DEDICATED TO MY BELOVED PARENTS
ABSTRACT
CHAPTER 1 INTRODUCTION
CHAPTER 2 REVIEW OF LITERATURE
CHAPTER 3 MATERIALS AND METHODS
CHAPTER 4 RESULTS
CHAPTER 5 DISCUSSION
CHAPTER 6 SUMMARY
CHAPTER 7 CONCLUSION
REFERENCES
APPENDIX
EFFECTS OF DIFFERENT LEVELS OF SUBMERGENCE AND NUTRIENTS ON BORO RICE (Binadhan-8) IN SALINE SOILS
MS THESIS
MD. ZAHIR RAIHAN
Department of Soil Science Bangladesh Agricultural University Mymensingh
June 2014
EFFECTS OF DIFFERENT LEVELS OF SUBMERGENCE AND NUTRIENTS ON BORO RICE (Binadhan-8) IN SALINE SOILS
A Thesis
Submitted to Bangladesh Agricultural University, Mymensingh In Partial Fulfillment of the Requirements for the Degree of Master of Science In Soil Science
By
Md. Zahir Raihan Roll No. 13 Ag. SS. JJ- 09M Semester: January-June, 2013 Registration No. 34162 Session: 2007-08
Department of Soil Science Bangladesh Agricultural University Mymensingh
June 2014
EFFECTS OF DIFFERENT LEVELS OF SUBMERGENCE AND NUTRIENTS ON BORO RICE (Binadhan-8) IN SALINE SOILS
A Thesis Submitted to Bangladesh Agricultural University, Mymensingh In Partial Fulfillment of the Requirements for the Degree of Master of Science In Soil Science By MD. ZAHIR RAIHAN Approved as to style and contents by
__________________________________ Prof. Dr. Abu Zofar Md.Moslehuddin Supervisor
_______________________________ Hafez Md. Ekram-ul Haque Co-supervisor
__________________________ Prof. Dr. Md. Anamul Haque Chairman Examination Committee & Head, Department of Soil Science
June 2014
Acknowledgements
ACKNOWLEDGEMENTS All praises are due to Almighty Allah who enabled me to complete a piece of research and prepare this thesis. At the outset, author express his heartfelt gratitude, ever indebtedness and deepest sense of respect to his honorable supervisor, Dr. Abu Zofar Md. Moslehuddin, Professor, Department of Soil Science, BAU, Mymensingh for his scholastic guidance, meaningful suggestions, and immense help in carrying out research and in preparing this thesis. The author extends his sincere appreciation to his reverend co-supervisor Hafez Md. Ekram-ul Haque, Principal Scientific Officer, Soil Science Division, BINA,Mymensingh for his valuable suggestions and sincere co-operation in preparing the thesis. The author is indebted to his respected teacher Professor Dr.Md.Anamul Hoque, Head, Department of Soil Science, BAU, Mymensingh for providing necessary facilities. The author wishes to extend cordial thanks to all other respected teachers of the Department for their encouragement and valuable advice to complete his Master’s study. The author is very pleased to extend thanks to Dr. Md. Mahbubul Alam (Tuton), Senior Scientific Officer, Soil Science Division, BINA, Mymensingh for his cordial co-operation in conducting field experiment, analyzing data, and encouragement in preparing the thesis. The author expresses thanks to Mohammad Forhad Hossain, Scientific Officer, Soil Science Division, BINA, Mymensingh for providing necessary information. The author expresses many thanks to all staff members of the laboratory, farm and office of Soil Science Division, BINA, Mymensingh. Thanks are extended to Md. Jahangir alam, Scientific Assistant, Soil Science Division, BINA, Mymensingh for his good help in analytical works and Md. Mortaba Ali (Manik) for neat typing. The author expresses extreme gratitude to his parents, sisters, brothers and relatives who have encouraged his to build up higher academic career and have sacrificed a lot and prayed always for his well beings.
The Author iv
EFFECTS OF DIFFERENT LEVELS OF SUBMERGENCE AND NUTRIENTS ON BORO RICE (Binadhan-8) IN SALINE SOILS
MD. ZAHIR RAIHAN ABSTRACT A field experiment was conducted at Kalikapur village of Kaliganj Upazila under Satkhira district in order to see the effects of flooding duration and additional application of K and S on Boro rice cv. Binadhan-8 in the saline area during from January to May 2013. The experiment was carried out in a split-plot design where the main plots comprised of five submergence levels viz. W 1 : continuous flooding, W 2 : submergence of field for 10 days (15 DAT), W 3 : submergence of field for 20 days (15 DAT), W 4 : submergence of field for 30 days (15 DAT), W 5 : submergence of field for 40 days (15 DAT), and the sub-plots of four additional nutrients rates viz. T 1: S 43 + K 25 , T 2 : K 38 , T 3 : S 32 + K 38 , T 4 : S 32 + K 38 (The suffices indicated amount of respective nutrients @ Kg ha-1) with three replications. The duration of flooding showed significant positive effect on the yield and yield components of Boro rice cv. Binadhan-8. The highest values for plant height (106.80 cm), panicle length (28.41 cm), plants hill-1 (15.32), grain yield (4.841 t ha-1), straw yield (6.466t ha-1) and biological yield (11.31 t ha-1) were recorded in continuous flooding (W 1 ) while these values were decreased with the decrease of the duration of field submergence from 40 days to 10 days. Additional application of K and S alsosignificantly influenced all of the parameters. Results revealed that the highest values for plant height (102.80 cm), panicle length (26.60 cm), plants hill-1 (15.44), 1000-grain weight (23.88g), grain yield (4.843 t ha-1), straw yield (6.045t ha-1), biological yield (10.89 t ha-1) and harvest index (44.56%) were obtained from T 3 where S and K were applied @ 32 and 38 Kg ha-1, respectively, in addition to the recommended fertilizer rate. The interaction of submergence and nutrients significantly manipulated the yield and yield attributes. Due to interaction of submergence and nutrients, the highest growth and yield was observed in continuous flooding with S 32 + K 38 (W 1 T 3 ). The single effect of submergence and nutrients, and their interaction were also found significant for K and S uptake by grain and straw and their total uptake. The highest amounts of total (grain + straw) K uptake (194.2 kg ha-1) and S uptake (24.24 kg ha-1) were recorded from continuous flooding, S 32 + K 38 (W 1 T 3 ). The results indicated that the treatment combination of continuous flooding and application of additional 38 Kg K and 32 Kg S per ha was the best option for increasing the yield potential of Binadhan-8 in saline soils of Bangladesh.
v
CONTENTS CHAPTER
TITLE
PAGE NO.
ACKNOWLEDGEMENTS
iv
ABSTRACT
v
LIST OF CONTENTS
vi
LIST OF TABLES
ix
LIST OF FIGURES
x
LIST OF APPENDICES
x
LIST OF ABBREVIATIONS
xi
1
INTRODUCTION
1
2
REVIEW OF LITERATURE
3
4-18
2.1
Effect of submergence on rice in saline area
4
2.2
Effect of nutrients on rice in saline area
13
2.2.1 Effect of potassium on rice in saline area
13
2.2.2 Effect of Sulphur on rice in saline area
15
MATERIALS AND METHODS
19-29
3. 1
Experimental site and soil
19
3.2
Collection and preparation of soils
19
3.3
Climate
21
3.4
Crop and variety
21
3.5
Land preparation
21
3.6
Treatments
22
3.7
Experimental design
22
3.8
Fertilizer application
24
3.9
Transplanting of rice seedlings
24
3.10
Intercultural operations
24
3.11
Submergence treatment
24
3.12
Harvesting and processing
25
3.13
Data collection and recording
25
vi
CONTENTS (Contd.) CHAPTER
TITLE 3.14 3.15 3.16 3.17
Procedure of data collection Soil analysis Plant analysis Statistical analysis RESULTS
4.1
Effect of submergence on Yield and yield contributing characters of Binadhan-8 4.1.1 Plant height 4.1.2 Panicle length (cm) 4.1.3 Number of Plants hill-1
4
4.1.4 1000-grain weight (g) 4.1.5 Grain yield 4.1.6 Straw yield 4.1.7 Biological yield 4.1.8 Harvest index (%) 4.2
Effect of nutrients on yield and yield contributing characters of Binadhan-8 4.2.1 Plant height 4.2.2 Panicle length (cm) 4.2.3 Number of Plants hill-1 4.2.4 1000-grain weight (g)
4.3
PAGE NO. 26 27 28 29 30-54
30 30 30 31 32 32 32 32 35 35 35 35 35
4.2.5 Grain yield 4.2.6 Straw yield 4.2.7 Biological yield 4.2.8 Harvest index (%) Interaction effect of submergence level and nutrients on Yield and yield contributing characters of Binadhan-8
36 36 37 37 39
4.3.1 Plant height 4.3.2 Panicle length (cm) 4.3.3 Number of Plants hill-1 4.3.4 1000-grain weight (g)
39 40 40 41
4.3.5 Grain yield 4.3.6 Straw yield
42 43 vii
CHAPTER
4
TITLE
4.4.1
4.4.2
5 6 7 8 9
4.3.7 Biological yield 4.3.8 Harvest index (%) Effects on Sulphur uptake by rice (Binadhan-8) 4.4.1.1 Effect of submergence S uptake by grain 4.4.1.2 Effect of submergence S uptake by straw 4.4.1.3 Effect of submergence total S uptake 4.4.1.4 Effect of nutrients S uptake by grain 4.4.1.5 Effect of nutrients S uptake by straw 4.4.1.6 Effect of nutrients total S uptake 4.4.1.7 Interaction effect of submergence and nutrients S uptake by grain 4.4.1.8 Interaction effect of submergence and nutrients S uptake by straw 4.4.1.9 Interaction effect of submergence and nutrients total S uptake Effects on potassium uptake by rice (Binadhan-8) 4.4.2.1 Effect of submergence K uptake by grain 4.4.2.2 Effect of submergence K uptake by straw 4.4.2.3 Effect of submergence total K uptake 4.4.2.4 Effect of nutrients K uptake by grain 4.4.2.5 Effect of nutrients K uptake by straw 4.4.2.6 Effect of nutrients total K uptake 4.4.2.7 Interaction effect of submergence and nutrients K uptake by grain 4.4.2.8 Interaction effect of submergence and nutrients K uptake by straw 4.4.2.9 Interaction effect of submergence and nutrients total K uptake DISCUSSION SUMMARY CONCLUSION REFERENCES APPENDICES
viii
PAGE NO. 44 44 47 47 47 47 48 48 48 49 49 49 51 51 51 51 52 52 52 53 53 53 55-56 57-58 59 60-68 69-71
LIST OF TABLES Sl. No.
Title
Page No.
1
Physical and chemical characteristics of the experimental field soil
20
2
Mean effect of submergence level on yield contributing characters of rice cv. Binadhan-8
31
3
Mean effect of submergence level on yield of rice cv. Binadhan-8
33
4
Mean effect of nutrients on yield contributing characters of rice cv. Binadhan-8
36
5
Mean effect of nutrients on of rice cv. Binadhan-8
37
6
Interaction effect of submergence level and nutrients on plant height (cm) of rice cv. Binadhan-8
39
7
Interaction effect of submergence level and nutrients on panicle length (cm) of rice cv. Binadhan-8
40
8
Interaction effect of submergence level and nutrients on plants hill1 of rice cv. Binadhan-8
41
9
Interaction effect of submergence level and nutrients on 1000 grain weight (g) of rice cv. Binadhan-8
42
10
Interaction effect of submergence level and nutrients on grain yield (t ha-1) of rice cv. Binadhan-8
42
11
Interaction effect of submergence level and nutrients on straw yield (t ha-1) of rice cv. Binadhan-8
43
12
Interaction effect of submergence level and nutrients on biological yield (t ha-1) of rice cv. Binadhan-8
44
13
Interaction effect of submergence level and nutrients on harvest index (%) of rice cv. Binadhan-8
45
14
Mean effect of submergence level on S uptake by rice cv. Binadhan-8
48
15
Mean effect of nutrients on S uptake by rice cv. Binadhan-8
49
16
Interaction effect of submergence level and nutrients on S uptake by rice cv. Binadhan-8
50
17
Mean effect of submergence level on K uptake by rice cv. Binadhan8
52
18
Mean effect of nutrients on K uptake by rice cv. Binadhan-8
53
19
Interaction effect of submergence level and nutrients on K uptake by rice cv. Binadhan-8
54
ix
LIST OF FIGURES
FIGURES
TITLE
PAGE NO.
3.1
Layout of the experiment
23
4.1
Effect of submergence level on grain and straw yield
34
4.2
Effect of nutrients on grain and straw yield
38
4.3
Interaction effect of submergence level and nutrients on grain yield
46
4.4
Interaction effect of submergence level and nutrients on straw yield
46
LIST OF APPENDICES PAGE NO.
APPENDIX
TITLE
I
Monthly record of air temperature, relative humidity and rainfall during the period from January to May, 2013
68
II
ANOVA for interaction effect of submergence level and nutrients on plant height (cm), panicle length (cm), number of plants hill-1 and 1000 grain weight (g) of rice cv. Binadhan-8
68
III
ANOVA for interaction effect of submergence level and nutrients on grain yield (t ha-1), straw yield (t ha-1), biological yield (t ha-1) and harvest index (%) of rice cv. Binadhan-8
69
IV
ANOVA for interaction effect of submergence level and nutrients on grain yield (t ha-1), straw yield (t ha-1) S uptake by rice cv. Binadhan-8
69
V
ANOVA for interaction effect of submergence level and nutrients on grain yield (t ha-1), straw yield (t ha-1) K uptake by rice cv. Binadhan-8
70
x
ABBREVIATIONS
AEZ
- Agro-ecological zone
Agril.
- Agricultural
BARC
- Bangladesh Agricultural Research Council
BAU
- Bangladesh Agricultural University
BBS
-Bangladesh Bureau of Statistics
BINA
- Bangladesh Institute of Nuclear Agriculture
BRRI
- Bangladesh Rice Research Institute
CV
- Coefficient of Variation
cv.
- Cultivar
DAT
- Days after Transplanting
et al.
- And others
FAO
- Food and Agriculture Organization
ILRI
- International Institute for Land Reclamation and Improvement
J.
- Journal
LSD
- Least Significant Difference
MoP
- Muriate of Potash
Res.
- Research
Sci.
- Science
Soc.
- Society
SRDI
- Soil Resource Development Institute
TSP
- Triple Super Phosphate
Var.
- Variety
Viz.
- Namely
%
- Percentage
Fig.
- Figure
xi
Introduction
CHAPTER 1
INTRODUCTION Rice (Oryza sativa L.) is the principal source of food for more than one third of the world’s population. It is rated as one of the major food crops in the world, but is also considered extremely salt-sensitive (Maas and Hoffman, 1977).It is deeply ingrained in
Bangladesh culture and even the words 'food' and 'rice' are synonymous in Bengali. It dominates over all other crops and covers 77% of the total cropped area and 93% farmers grow rice. The total area and production of rice in Bangladesh are about 11.7 million hectares and 31.98 million metric tons, respectively (BBS, 2011). Salinity is an environmental challenge affecting crop production seriously all over the world. Over 800 million hectares of land throughout the world are salt-affected, either by salinity (397 million ha) or the associated condition of sodicity (434 million ha) (FAO, 2005). In Bangladesh, salinization is one of the major natural hazards hampering crop production. Coastal area constitutes 20% of our country of which about 53% were affected by different degrees of salinity (Islam, 2005). Salinity has emerged as a major factor responsible for the crop production at a lower rate in Bangladesh. It is anticipated that regulation of fresh water from upstream, irregular rainfall, introduction of brackish water for shrimp cultivation, faulty management of sluice gate ,and polders, regular saline tidal water flooding in unprotected area, capillary rise of soluble salt s etc. are the main causes of increased soil salinity in the top soil of coastal region. A comparative study of the salt affected area between 1973 to2009 showed that about 0 .223 million ha (26.7%) new land have been affected by various degree of salinity during about the last four decades. It was also found that about .0354 million ha new land have been affected by various degree of salinity during last 9 years only (2000-2009). Various agricultural regions have significantly lost their productivity due to soil salinity in last several decades. The worst salinity conditions are reported from the Khulna, Bagerhat, Satkhira and Patuakhali districts (SRDI, 2010).
1
Introduction
Submergence or flooding duration has important effect in decreasing soil salinity and increasing rice yield under these conditions. The dissolution of salt through the maintenance of submergence by fresh water on the surface of the rice crop produce favorable conditions for plant development and rapidly enables reduction to take place. The effect of contact from the rising saline water table under pressure can also be reduced by dilution in the layer of fresh water (Maeght et al., 2005). The best method to use saline water was intermittent irrigation at FC with EC = 2 dS m-1. In case of more salinity, mixing fresh and saline water and intermittent irrigation can mitigate the severe effects of salinity on rice (Rezaei et al., 2013).Maximum growth and economic yields of rice can be obtained from continuous flooding and the lowest result comes under the moist regime (Singh and Mishra, 1990). Salinity from irrigation can occur over time wherever irrigation occurs; since almost all water (even natural rainfall) contains some dissolved salts. When the plants use the water, the salts are left behind in the soil and eventually begin to accumulate. Since soil salinity makes it more difficult for plants to absorb soil moisture, these salts must be leached out of the plant root zone by applying additional water. Salinization from irrigation water is also greatly increased by poor drainage and use of saline water for irrigating agricultural crops (ILRI, 1989).
Nutrients play essential roles for successful crop production in saline soil. Among the nutrients potassium and sulphur help in reducing soil salinity and play a major role in achieving the maximum growth and economic yields of rice in saline area. Qadar (1998) referred that K+ addition to Saline culture solution markedly improved rice yield and yield attributes as a results of increasing K+ uptake and decreasing Na+ uptake. Gypsum is the most commonly used amendment for sodic soil reclamation and for reducing the harmful effects of high sodium irrigation water sin agricultural areas because of its solubility, low-cost, availability and ease of handling (Amezketa et al., 2005). Studies on the effect of gypsum application on saline-sodic soil reclamation have shown that the soil receiving gypsum at higher rate removes the greatest amount of Na+ from the soil 2
Introduction
columns and causes a substantial decrease in soil electrical conductivity (EC) and sodium adsorption ration (Hamza et al., 2003).The application of gypsum could alleviate the adverse effects of salinity and increase tolerance to salinity in rice plants (Sharma, 2001). In Bangladesh population is increasing but the crop yield per unit area shows a decreasing trend due to poor management practices of soil nutrients and irrigation especially in saline area. It appears from the foregoing discussions that knowledge or comparative study of soil nutrients and irrigation on saline soils of dry and wet season are very important for successful crop production. In view of the above facts, the present study was conducted in the selected saline areas of Bangladesh with the following objectives: i)
To investigate the effect of submergence in rice production in saline area.
ii)
To study the effect of different nutrient management on soil salinity for rice production.
iii)
To know the interaction effect of different levels of submergence and nutrient management on soil salinity for rice production.
3
Review of Literature
CHAPTER 2
REVIEW OF LITERATURE This chapter presents a comprehensive review of the research information relating to the effects of submergence and nutrients on rice cultivation on the yield, yield contributing characters and nutrient uptake of rice. It is the most popular and common food crop in Bangladesh. Many experiments have been conducted at home and abroad on the nutritional requirements of rice. Different level of submergence and nutrients are applied to conduct the rice production. A review of literature related to pertinent research is presented below. 2.1 Effect of submergence on rice in saline area Rezaei et al. (2013) conducted a pot experiment in order to study the effects of salinity stress as well as water stress on rice at Rice Research Institute of Iran. Five water salinity levels: fresh water (EC = 1 dS m-1), 2, 4, 6 and 8 dS
m-1
and five
irrigation regimes: continues flooding, Alternative Wetting and Drying (AWD), intermittent irrigation at 100, 90 and 80 percent of field capacity (FC) were considered as irrigation treatments. Fresh water produced the highest yield, 18.57 gr pot-1, whereas, the yield in salinity levels of 2, 4, 6 and 8 ds m-1 were 13.78, 5.78, 3.61 and 0.74 gr pot-1, respectively, with the yield losses of 25, 70, 80 and 97%, respectively. Intermittent irrigation at FC produced the highest yield. The yield increased 8 and 13% in AWD and intermittent irrigation at FC treatments respectively, while it decreased 8 and 27% in intermittent irrigation at 80 and 90% of FC treatments as compared with continues flooding treatment. This study showed that the best method to use saline water was intermittent irrigation at FC with EC = 2 dS m-1. In case of more salinity, mixing fresh and saline water and intermittent irrigation can mitigate the severe effects of salinity on rice. Nosratollah (2013) stated that changes in pH, EC and concentration of phosphorus (P) in soil solution during submergence and rice (Oryza sativa. L.cv. Khazar) growth period were studied in three paddy soils of north of Iran (one acid and two alkaline-calcareous soils) with and without P fertilizer application. In P 4
Review of Literature
fertilized treatments, 40 mg P per kg of soil was added as triple superphosphate. The experiment was performed in a set of specially fabricated pots equipped with a perforated sampling tube installed in the root zone area. The results showed that after submergence, water soluble-P increased initially and then decreased in all three soils in both cultivated and uncultivated treatments. Rice cultivation in soils decreased significantly pH and concentration of water soluble-P compared to the uncultivated soils. After submergence, the pH of alkaline soils decreased, while the pH of acid soil increased significantly. Hague (2012) conducted a field experiment tidal submergence increased K uptake of rice. The K uptake by BR23 under tidal water was about 47, 43 and 8 kg/ha more than those recorded with ground water irrigation under absolute control, K omission and K addition treatments respectively, whereas it was 31, 21, and 68 kg/ha. The results indicated that whether fertilizers were applied or not plants absorb considerable amount of K from tidal water. Endo et al. (2011) selected farmlands in southern Baja California, Mexico, were surveyed to determine the levels and the causes of salinization/sodication in irrigated agricultural soil. The salt dynamics observed in profiles differed from farm to farm. Low EC and high pH levels were observed in the profiles of sandy fields, because the salt composition of these soils can easily change when salts are leached by irrigation water that contains carbonates of sodium. On the other hand, high levels of salinity and sodicity were observed in the soils of clayey fields.
Soil
salinization/sodication
is
complexly
interrelated
with
soil
characteristics, the amount and composition of salts in the soil, the quantity and quality of irrigation water applied, and the irrigation methods used. Our findings indicate that irrigation water in Baja California should be supplied at a rate that is sufficient to meet crop requirements without exacerbating salt accumulation.
Bailey et al. (2010) studied that many lowland rice cultivars, despite having an ability of internal aeration, are still sensitive to complete submergence. Their leaves and stems moderately elongate under complete submergence to reach the 5
Review of Literature
air-water interface, but their elongation growth can exhaust energy reserves and cause death when the flooding depth is deep and the flooding period is long. Haque (2010) reported tidal submergence is an important source of phosphorus. It increases all the growth parameters along with yield of rice. It supplies considerable quantities of phosphorus however; it could not meet the total phosphorus requirement of rice. Tidal submergence increases P uptake of rice. Phosphorus uptake from tidal water treatments increased when plants were supplied with N and K fertilizer. Tidal submergence contributed about 5-6 kg P/ha in P omission plot and about 12-14 kg P/ha in plots with added P. Sahrawat (2010) examined that the decomposition of OM in aerobic soils is rapid in the presence of oxygen, which is the most efficient electron acceptor. On the other hand, in the absence of oxygen in flooded soils or submergence and sediments, decomposition of OM depends on the availability of alternate electron acceptors such as NO 3- , SO 4 2- or Fe2-. Since iron is present in high amounts in rice soils, the ferric-ferrous iron redox reaction plays a dominant role in the oxidation of OM and its mineralization in submerged soils and sediments.
Colmer and Voesenek (2009) conducted a field experiment some cultivars use two distinct strategies of growth controls to survive under submerged conditions. One of the strategies is a quiescence strategy [i.e., the low-oxygen quiescence syndrome in which shoot elongation is suppressed to preserve carbohydrates for a long period (10-14 days) under flash-flood conditions. Submergence-tolerant cultivars can restart their growth during de submergence by using preserved carbohydrates. Another strategy is an escape strategy [i.e., the low-oxygen escape syndrome which involves fast elongation of internodes to rise above the water level and is used by deep water rice cultivars. Nayak et al. (2009) reported that replacement of dry season flooded rice crop by maize caused a reduction in C and N sequestration in the soil. The results demonstrated the capacity of continuous irrigated lowland rice system to sequester C and N during relatively short time periods and were in accord with 6
Review of Literature
those reported by other researchers on the long-term benefits of flooding on soil OM accumulation. Nie et al. (2009) stated that the overall role of production (crop rotations or intercropping) systems and nutrient and water management assume greater importance in the sustainability of the system as a whole. The critical limits for deficiency and toxicity of nutrients vary in flooded or submergence and nonflooded rice ecology and there is need for research in this important area for optimizing nutrient management strategy in aerobic rice. Colmer and Pedersen (2008) studied that the unlike other crop plants, rice has some adaptive traits for tolerance of submergence. One of the traits is formation of the longitudinal interconnection of gas spaces, called aerenchyma that enables internal aeration between shoot and roots.
Pampolino et al. (2008) reported that prolonged submerged soil conditions stimulate SOM accumulation and C sequestration in wetland soils and sediment. Belder et al. (2005) observed that with the land use change from paddy to aerobic rice is likely to have a reverse influence on the fertility benefits derived from soil submergence.This has implications for the growth and yield of aerobic rice through the depletion of soil organic matter and nitrogen. The availability of some nutrients especially micronutrients such as Mn and Fe on calcareous soils Yousefi (2006) reported that alternative irrigation reduced effect of salinity tension and attributed it to less absorption of water and saline solvable in water and as a result to less accumulation of salt in plant tissue. She also reported that in AWD, the effects of saline water will be alleviated. Maeght et al. (2005) the differences of pH values during submerged and dry conditions are important. These cyclic evolutions, which follow the seasons, cannot perhaps bring a return to initial state but may produce a differentiation of pH values. The dissolution of salt through the maintenance of submergence by fresh water on the surface of the rice crop produce favorable conditions for plant 7
Review of Literature
development and rapidly enables reduction to take place. The effect of contact from the rising saline water table under pressure can also be reduced by dilution in the layer of fresh water. Hassan and Karim (2002) conducted field experiment on mustard adopting seed placement techniques along with leaching practices using saline river water. Analysis of data reveled that irrigation with saline river water through fulfilling the leaching requirement and seed placed on the drain slope have been proved to be a successful water management technique to obtain optimum yield of mustard in saline area. Sahrawat and Narteh (2002) studied the pre-flooding of the soil for about four weeks prior to transplanting of the rice
seedlings leads to the release of
ammonium, P, K and other exchangeable ions in soil solution, which is good for growth of the rice plant. Jun Lu et al. (2000) in most cases, rice production is associated with flooding irrigation and the efficiency of irrigated water use is generally lower for production of rice than for other crops. We have examined the effects of various irrigation regimes on water consumption in a well-puddled paddy field, as well as on dry matter production, grain yield and physiological responses of the plants. Four sets of conditions were studied, with two replications, in the wellpuddled paddy field: continuous flooding irrigation treatment (CSF); three intermittent irrigation treatments, designated II-0, II-1 and II-2, in which plants were re-irrigated when the water potential of the soil fell below 0, –10, and –20 kPa at a depth of 5 cm, respectively. Intermittent irrigation led to the repeated shrinking and swelling of soil during II-1 and II-2 and, therefore, soil cracks developed rapidly. There were no significant differences in dry matter production and grain yield between CSF and II-0, but both were significantly greater than in the case of II-1 and II-2 Early senescence with ripening and water stress around midday decreased the rate of photosynthesis in leaves, causing the lower NAR. These physiological responses of the plants were responsible for the reduction on the dry matter production and grain yield in the intermittent irrigation. 8
Review of Literature
Narteh and Sahrawat (1999) said that submergence of soil improves the availability of ammonium-N, P, K,calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), and silicon (Si). Toxic concentrations of Al and Mn in soil solution are minimized with reduced solubility of these metals as a result of increased pH. On the other hand, the availability of S may be reduced due to sulfate reduction to sulfide in flooded soils. The supply of micronutrients such as copper (Cu) and molybdenum (Mo) is generally adequate. The availability of zinc (Zn) is reduced in submerged soils. Ragab et al. (1999) studied the use of alternative water resources such as brackish water (groundwater), seawater, desalination of saline water, etc. by adopting an integrated management approach for irrigation, drainage and leaching. A Model is being developed to predict the long-term effect of using saline water on soil and the environment, on crop yield, on soil water, and on soil salinity profiles under different strategies of water management. Blending alternate use of fresh and saline waters help to reduce soil salinity as well as improve crop yield. Neue et al. (1997) studied that the most important factor responsible for net accumulation of OM in wetland soils and sediments is the high net primary productivity of these systems In essence, slow decomposition of OM and higher net primary productivity of submerged rice soils lead to net accumulation of organic matter and N in submerged soils and sediments. Ibrahim et al. (1995) two experiments, one in each of the 1991 and 1992 rice growing seasons were conducted at the Sakha Agricultural Research Station in the Nile Delta to determine the effect of irrigation scheduling on grain and straw yield of transplanted rice. The drought tolerant variety ITT, showed no significant difference in yield due to irrigation interval ranging from 6 to 10 days. For the lowland variety Giza 172, one of the common varieties in Egypt, irrigation intervals should be every 6 days for approximately one month after transplanting. Irrigation intervals can then be extended to 10 days until the end of the growing season without decreasing yield.
9
Review of Literature
BINA (1995) found that there was no interaction effect on irrigation and cultivars but all the characters were increased under continuous ponding (3-5 cm) which contributed there to produce significantly higher yield. From the experiment it was also found that continuous submergence required the higher amount irrigation water but yield obtained in continuous submergence was around 10% higher over the treatments of irrigation 1, 2, 3, 4 or, 5 days after pond water drainage. From the experiment it revealed that 5 days after pond water drainage was better to produce optimum yield with minimum water use. Gowda (1995) studied the effects of submergence throughout the growth period, saturation until panicle initiation and submergence thereafter or saturation throughout the growth period on yield of rice cv.J13 Madhu and Pusha. Grain yield was highest with submergence and lowest with saturation throughout the growth period. Madhu gave the lower grain yields than J13 or Push in both years. Water use efficiency was highest with saturation. Mastan and Vijay Kumar (1993) reported that grain yield with continuous submergence was 5.5 t ha-1, while water use 1530 mm. Yield and water requirement decreased with increasing delay in applying water after the disappearance of pond water, and were 3.4 t ha-1 and 680 mm with a 5 days delay. Singh et al. (1991) reported that continuous submergence grain yield was positively correlated with number of grains panicle-1, harvest index and straw yield. Under wetting and drying panicle length, number grains panicle-1, 1000grain weight, harvest index and straw yield were positively correlated with grain yield. Kumar et al. (1988) reported that rice grown on a sandy clay loam soil with 5 cm irrigation applied 2 days after the disappearance of pond water or under continuous submergence gave similar paddy yields in the year when the water table was deep. The potential saving was 11-32% in irrigation water when applied 2 days' after the disappearance of ponds water compared to continuous submergence. Water loss through deep percolation was accelerated under continuous or partial submergence. 10
Review of Literature
Goel and Verma (1988) conducted a field experiment the out of 6 water management practices tested for rice in 1984-85, submergence up to the tillering stage followed by irrigation at 4 days intervals up to 50% flowering and there after 5 cm irrigation to keep the soil at saturation up to harvest gave the highest average paddy yields of 7.09 t ha-1 . Marimithu and KulandaiVelu (1987) stated that continuous flooding up to 5 cm depth and partial rotation (irregular and intermittent) irrigation gave the best grain yields in the wet and dry season, respectively. BRRI (1986) found that the optimum yield (5.0 t ha-1) and water application (1639 mm) were achieved in the treatment of 5 days interval. Minimum water applications were in the 10, 15, and 20 days intervals but the yields were very poor. Alva and Nielson (1980) concluded that grain yield of rice was found to increase with the increase of water availability.
Krishnamurthy et al. (1980) stated that 5 cm submergence of soil was the best for rice yield in rabi season, and Marimuthu and Kulandaivelu (1987) got the similar type of result in the summer season.
Ponnamperuma (1975) found the growing rice under non-flooded moisture regime likely would influence soil fertility and nutrient availability and this understandably has implications for the growth and productivity of aerobic rice. Such soil quality and fertility effects could range from overall depletion of soil organic matter and nitrogen to the availability of nutrients such as P on acid soils and micronutrients such as Mn and Fe on calcareous soils
Khare et al. (1970) found that the highest average paddy were obtained at 5 cm flooding, followed by 15 cm flooding and then saturation with no flooding Highest yield with 5cm flooding was increased tillering and ear length. 11
Review of Literature
2.2 Effect of nutrients on rice in saline area 2.2.1 Effect of potassium on rice in saline area Wang et al. (2012) reported that at high salinity (125 mmol/L NaCl), however, Ca2+ did not have any effects on Na+, K+ accumulation and K+/Na+ ratios in plants. Further analysis showed that, at low salinity, the addition of Ca2+ significantly enhanced the selective absorption and transport capacity for K+ over Na+ in rice. Although Na+ efflux and Na+ influx were remarkably reduced by Ca2+ under both low and high salt stresses, their ratio was lowered only under low salt stress. In summary, these results suggest that Ca2+ could regulate K+/Na+ homeostasis in rice at low salinity by enhancing the selectivity for K+ over Na+, reducing the Na+ influx and efflux, and lowering the futile cycling of Na. Ebrahimi et al. (2012) showed that soil salinity affected growth and yield component parameters in most of the cases. Potassium application alleviated the stress condition and significantly improved dry matter yield and yield components in rice. Grain, straw, total biological yield, harvest index, 100 seeds weight ,root dry weight and total tillers significantly decreased with increasing salinity but grain protein increased with increasing salinity. The interaction between salinity levels and methods of potassium application was significant only for root dry weight. Mohiti et al. (2011) reported that number of tillers increased significantly (P 100% GR + 20 Mgfed-1 WHC > 50% GR + 10 Mgfed-1 RSC > 50% GR + 10 Mgfed-1 WHC > 100% GR > RSC > WHC > control. This study suggests that application of gypsum combined with WHC or RSC enhanced reclamation and caused more decreases in salinity as well as sodicity.
Cha-um et al. (2011) stated to remediate saline soil using gypsum and/or FYM before the cultivation of rice. Subsequently, the physiological and morphological characters of the rice plants, as well as crop yield, were evaluated. In this study, rice grown in soil with the application of gypsum and FYM had 79.6% spikelet fertility, while rice grown in soil without the gypsum and FYM treatment had only 46.4%. The low sodium ion accumulation in gypsum and FYM treated rice 15
Review of Literature
was positively related to water use efficiency and pigment stabilization, leading to high efficiency of photosystem II (ΦPSII), and net-photosynthetic rate (Pn). The sugar content in the flag leaf of rice cultivated with gypsum and FYM treatment was enriched, leading to high productivity. The exogenous application of gypsum and FYM in saline fields may be used as effective remediation, which will lessen plant defects caused by the contaminating salts in saline soil. Silveira et al. (2008) stated that inadequate management of soil and irrigation water contribute to soil degradation, particularly in the alluvial areas of Northeast Brazil, where salinity and sodicity are already common features. This study evaluates the effects of the addition of gypsum in the irrigation water on physical and chemical properties of soils with different levels of salinity and sodicity. Leaching tests using simulated irrigation water classified as C 3 S 1 , and gypsumsaturated irrigation water were carried out in soil columns of 20 and 50 cm depth. Soil leaching with gypsum saturated water (T 2 ) resulted in an increase in the amounts of exchangeable calcium and potassium, and in a decrease of soil pH, in relation to the original soil (T 0 ), with significant statistical differences to the treatment using only water (T 1 ). Gypsum saturated water improved the hydraulic conductivity in both layers. The use of gypsum in the irrigation water improved soil physical and chemical properties and should be considered as an alternative in the process of reclamation of saline-sodic and sodic soils in Northeast Brazil. Khattak et al. (2007) conducted Pot experiment to evaluate the effect of various doses of gypsum on the yield of crops and properties of salt affected soils at Agricultural Research Institute. Earthen pots eighteen (18) in number were filled with this soil. There were six treatments comprising of gypsum @ 0, 25, 50, 75, 100 and 200 % of the gypsum requirement (G.R.). After the harvest of rice, every pot soil was analyzed for pH, EC and G.R. Then every pot soil was remixed and wheat was grown in it at field capacity without further addition of gypsum. Initial 5 leachates of drained water of all the pots were collected after respective irrigations and checked for the same characteristics, which were done during rice 16
Review of Literature
crop. The results showed that pH, EC, and SAR of the leachate samples were decreased with increasing level of gypsum and with the number of leachates. EC and SAR decreased considerably relative to pH. Gypsum application in different doses increased yield of rice by 9.8 to 25.3% and that of wheat crop by 10-80% over control treatment. Maximum increase occurred with the application rate of 200% of G.R. in both the cases. The data further indicated that soils were also improved with gypsum application especially with respect to pH and SAR
Hanay et al. (2004) examined that use of gypsum, calcite, calcium chloride, and other chemical agents that provide Ca, which tends to replace exchangeable Na, is effective for saline soil amelioration.
Bajwa and Josan (2003) conducted a field experiment to examine the influence of different amounts of gypsum, applied either each irrigation or in one dose, on the amelioration of deteriorating effects of sodic water irrigations under a fixed ricewheat cropping cycle. Application of gypsum decreased pH, SAR and ESP of the top 0-60 cm soil and hence increased yields of crops. Increase in levels of gypsum progressively decreased the Na saturation of the soil. In rice, small amounts of gypsum applied in one dose were less beneficial.
Chandel et al. (2002) conducted an experiment to study the effect of S applied to rice and mustard grown in sequence on the growth and yield of rice at the Research Farm, BHU, Varanasi, and Uttar Pradesh, India. Four main plots (rice) S rates (0, 15, 30 and kg ha-1) and three sub-plots (mustard) S rates (0, 20 and 40 kg ha-1) were laid out in a split-pilot design and S were supplied as SSP. They stated that increasing S levels in rice significantly improved growth attributes i.e. tiller number, leaf number and dry matter production; yield traits such as harvest index of rice up to 45 kg ha-1; however, 45 and 30 kg S ha-1 treatments were at par.
17
Review of Literature
Mandal et al. (2000) carried out a greenhouse experiment to evaluate the effect of N and S fertilizers on nutrient content of rice grain (cv. BR 3) at various growth stages (tillering, flowering and harvesting). Nitrogen was applied as urea and S as gypsum at 0, 5, 10 and 20 kg S ha-1. The combined application of these 2 elements increased the straw and grain yields significantly.
Sarkunan et al. (1998) carried out a pot experiment to find out the effect of P and S on the yield of rice under flooded condition on a P and S deficient sandy loam soil. The treatments were the combination of 4 levels of P (0, 25, 50 and 100 mg kg-1 soil) as ammonium phosphate and 4 levels of S (0, 10, 25 and 50 mg kg-1 soil) as ammonium sulphate. Increasing levels of P from 0-100-mg kg-1 progressively increased the grain yield from 16.9 to 42.5 g pot-1. Sulphur addition at 25 g kg-1 resulted in 9% increase in grain yield. The treatment combination of 100 mg P and 10 mg S kg-1 soil gave significantly higher grain yield than the other treatments.
18
MATERIALS AND METHODS
CHAPTER 3 MATERIALS AND METHODS This chapter describes the experimental aspects of the study. The field experiment was conducted at Kalikapur of Kaliganj upazila under Satkhira district to see the effects of flooding duration and additional application of K and S on Transplanted Boro rice cv. Binadhan-8. The materials used and the methods followed have been presented in this chapter. 3.1 Experimental site and soil The experiment was carried out at Kalikapur in Kaliganj upazila under Satkhira district during the period from January to May 2013. Experimental site was located 22.4500°N latitude and 89.0417°E longitude, the elevation was two meter from the mean sea level. The experimental site belongs to the Agro-ecological Zone of the Ganges Tidal Flood Plain. The General Soil Type of the experimental plot was the Calcareous Dark Grey Floodplain Soils. The experimental soil is clays in texture having the soil pH value 6.1. Among the nutrients, the N, P and Zn contents of this soil are especially low. The salinity of water in the experimental site was gradually increased from January to May 2013 except February month which were 3.70, 2.90, 4.50, 5.31, 8.8 dS m-1, respectively.
3.2 Collection and preparation of soilsThe soil samples were collected at a depth of 0-15 cm from 10 different spots of the experimental field. The samples were put together to make a composite soil sample. The unwanted materials like stones, gravels, pebbles, plant roots, etc. were removed from the soil. Then, the soil samples were air-dried and the clods were broken, ground to pass a 2-mm (10mesh) sieve, was kept in a plastic bottle for initial physical and chemical analysis. The data are presented in Table 3.1. 19
MATERIALS AND METHODS
Table 3.1 Physical and chemical characteristics of the experimental field soil Location
Kalikapur, Kaliganj, under Satkhira district
Agro-ecological zone AEZ)
Ganges Tidal Floodplain,
Land type
Medium Lowland
General soil type
Calcareous Dark Grey Floodplain Soils
Drainage
poor
Elevation
2 meter above the mean sea level
Consistency
Friable when moist
Vegetation
Rice
Characteristics
Value
1. Particle size distribution a. % Sand (2-0.05 mm)
11.64
b. % Silt (0.05 -0.002mm)
32.0
c. % Clay ( W 5 > W 4 > W 3 > W 2 (Table 4.1). The highest number of plants hill-1 (15.32) was observed in continuous flooding (W 1 ). The lowest (12.35) was recorded in submergence of field for 10 days (W 2 ). The plants hill-1 were statistically similar at W 3, W 4 and
W 5 treatments, which was
less than the highest value obtained from continuous flooding. 4.1.4 1000-grain weight (g) Analysis of variance of data showed the submergence effect on 1000-grain weight (g) was not statistically significant (Table 4.1). The 1000-grain weight ranged from 22.87 to 23.90 g. The 1000 grain weight followed the order of W 5 > W 2 > W 4 > W 1 > W 3 (Table 4.1). The highest 1000-seed weight (23.90g) was observed in Submergence for 40 days (W5) and the lowest (22.87g) was observed in submergence of field for 20 days (W3).
Table 4.1.Mean effect of submergence level on yield contributing characters of rice (cv. Binadhan-8) Level of submergence W 1 :continuous Flooding W 2 : submergence of field for 10 days(15DAT) W 3 : submergence of field for 20 days (15DAT) W 4 : submergence of field for 30 days (15DAT)) W 5 : submergence of field for 40 days (15DAT)) LSD 0.05
Plant height (cm)
Panicle length (cm)
Number of plants hill-1
1000 grain weight (g)
106.80 a
28.410 a
15.32 a
23.40
98.29 d
25.30 d
12.35 c
23.77
99.60 c
25.31 d
12.88 bc
22.87
100.10 bc
26.09 c
13.00 bc
23.57
101.00 b
26.31 b
13.85 b
23.90
0.960
0.174
1.03
0.764
Values in a column having common letters do not differ significantly at 5% level of significance. .
31
RESULTS
4.1.5 Grain yield Grain yield of rice is the ultimate product of yield components which was greatly influenced by submergence levels (Table 4.2, and Fig. 4.1). The highest grain yield (4.841 t ha-1) was observed in continuous flooding (W 1 ) where the lowest (3.935t ha-1) was observed in submergence of field for 10 days (W 2 ). Result revealed that grain yield at W 3, W 4 and W 5 were statistically similar. 4.1.6 Straw yield With regard to the conclusions of the result of submergence (Table 4.2 and figure 4.1), effectiveness of different growth stage on weight of straw was significant. The highest straw yield (6.466t ha-1) was observed in continuous flooding (W 1 ) and the lowest (5.155 t ha-1) was recorded in submergence of field for 10 days (W 2 ). Result revealed that straw yield at W 2 and W 3 were statistically similar as well as W 4 , W 5 were statistically similar. 4.1.7 Biological yield Results presented in the Table 4.2 showed that submergence had significant effect on the biological yield. It was observed that the treatments continuous flooding (W1) gave the highest Biological yield(11.31 t ha-1).The lowest biological yield (9.090 t ha1)
was obtained from submergence of field for 10 days (W2).
4.1.8 Harvest index (%) Table 4.2 reveals that the effect of submergence on harvest index was statistically significant (Table 4.2). The highest HI (45.26%) was recorded in submergence for 20 days (W 3 ) and the lowest HI (42.74%) was observed in continuous flooding (W 1 ). Result showed that HI decreased with increased submergence.
32
RESULTS
Table 4.2.Mean effect of submergence level on yield of rice (cv. Binadhan-8) Submergence level W 1 :continuous flooding W 2 : submergence of field for 10 days(15DAT) W 3 : submergence of field for 20 days (15DAT) W 4 : submergence of field for 30 days (15DAT)) W 5 : submergence of field for 40 days (15DAT))
Grain yield Straw yield (t ha-1) (t ha-1)
Biological yield (t ha-1)
HI (%)
4.841 a
6.466 a
11.31 a
42.74 b
3.935 e
5.155 c
9.09 e
43.21 b
4.282 d
5.174 c
9.456 d
45.26 a
4.439 c
5.790 b
10.23 c
43.40 b
4.597 b
5.918 b
10.52 b
43.72 b
LSD 0.05
0.148
0.234
0.249
1.09
Values in a column having common letters do not differ significantly at 5% level of significance.
Legend: W 1 = continuous flooding, W 2 = submergence of field for 10 days (15 DAT) W 3 = submergence of field for 20 days (15 DAT) W 4 = submergence of field for 30 days (15 DAT) W 5 = submergence of field for 40 days (15 DAT)
33
RESULTS
7 Grain
Straw
6
-1
Yield (t ha )
5
4
3
2
1
0 W1
W2
W3
W4
Submergence level
Fig. 4.1 Effect of submergence on grain and straw yield
Legend: W 1 = continuous flooding, W 2 = submergence of field for 10 days (15 DAT) W 3 = submergence of field for 20 days (15 DAT) W 4 = submergence of field for 30 days (15 DAT) W 5 = submergence of field for 40 days (15 DAT)
34
W5
RESULTS
4.2 Effect of nutrients on yield and yield contributing characters of Binadhan-8 4.2.1 Plant height There was a significant effect of nutrients on plant height (Table 4.3). The highest plant height (102.80 cm) was observed from S 32 + K 38 (T 3 ). The lowest plant height (99.56 cm) was produced from K 38 (T 2 ).Result revealed that plant height at T 1 and T 4 were statistically similar. 4.2.2 Panicle length (cm) Result showed that (Table 4.3) nutrients had significant effect on panicle length. The longest panicle (26.60 cm) was found from S 32 + K 38 (T3) and the shortest (26.01 cm) was obtained from K 38 (T 2 ). It indicated that panicle length at T 2 and T 4 are statistically similar 4.2.3 Number of plants hill-1 As observed in the (Table 4.3) there was a significant effect of nutrients in terms of the production of plants hill-1.The highest number of Plants hill-1 (15.44) was obtained from S 32 + K 38 (T 3 ) and the lowest number of Plants hill-1 (12.23) found from K 38 (T 2 ).Result revealed that number of plants hill-1 at T 2 and T 4 were statistically similar. 4.2.4 1000-grain weight (g) Thousand grain weight of rice was significantly influenced by different nutrients (Table 4.3). Thousand grain weight followed the order of T 1 =T 3 >T 4 >T 2 (Table 4.1). Apparently the highest 1000-grain weight (23.88g) was recorded from S 32 + K 38 (T 3 ) and the lowest 1000-grain weight (23.00g) was found in K 38 (T 2 ).Result showed that 1000-grain weight (g) at T 1 and T 3 were statistically similar, again those of T 2 and T 4 were also statistically similar to each other.
35
RESULTS
Table 4.3: Mean effect of nutrients yield contributing characters of rice (cv. Binadhan-8)
Nutrients
Plant height (cm) 101.30 b
Panicle length (cm) 26.37 b
Number of Plants hill-1 13.45 b
1000 grain weight (g) 23.88 a
T 2 (K 38 )
99.56 c
26.01 c
12.23 c
23.00 b
T 3 ( S 32 + K 38 )
102.80 a
26.60 a
15.44 a
23.88 a
T 4 (K 50 )
100.90 b
26.16 c
12.80 c
23.26 b
LSD 0.05
0.847
0.145
0.629
0.568
T 1 (S 43 +K 25 )
Values in a column having common letters do not differ significantly at 5% level of significance.
4.2.5 Grain yield Grain yield is the main parameter of this study. Rice grain yields are highly dependent upon the number of panicle-bearing tillers produced per plant. Nutrients had significant effect on grain yield (Table 4.4, Fig. 4.2). The highest grain yield (4.843 t ha-1) was obtained from S 32 + K 38 (T 3 ) and the lowest grain yield (4.021t ha-1) was found in K 38 (T 2 ). 4.2.6 Straw yield Unlike other parameters, there was a significant effect of nutrients on straw yield (Table 4.4, figure 4.2). The highest straw yield (6.045t ha-1) was observed from S 32 + K 38 (T 3 ) and the lowest straw yield (5.310t ha-1) was produced in K 38 (T 2 ).The straw yield due to different treatments ranked in the order of T 3 > T 1 > T 4 > T 2 . 4.2.7 Biological yield (tha-1) Similar to plant height, Biological yield responded significantly to nutrients application (Table 4.4). The highest biological yield (10.89 t ha-1) was obtained from S 32 + K 38 (T 3 ) and the lowest biological yield (9.33 t ha-1) was obtained from K 38 (T 2 ).which is statistically almost similar with the yield obtained from other treatments. 36
RESULTS
4.2.8 Harvest index (%) The influence of nutrients on harvest index was significant (Table 4.4). The experimental results showed that the highest harvest index (44.56%) was obtained from (S 32 + K 38 ) (T 3 ) and the lowest harvest index (43.15 %) were obtained from K 38 (T 2 ). Result showed that Harvest index (%) at T 1 and T 3 were statistically similar, again those of T 2 and T 4 were also statistically similar to each other. Table 4.4: Mean effect of nutrients on yield of rice (cv. Binadhan-8) Nutrients
Grain yield (t ha-1)
Straw yield (t ha-1)
Biological yield (t ha-1)
Harvest index (%)
T 1 (S 43 + K 25 )
4.536 b
5.818 b
10.36 b
43.80 ab
T 2 (K 38 )
4.021 d
5.31 d
9.331 d
43.15 b
T 3 ( S 32 + K 38 )
4.843 a
6.045 a
10.89 a
44.56 a
T 4 (K 50 )
4.274 c
5.629 c
9.903 c
43.16 b
LSD 0.05
0.115
0.153
0.178
0.827
Values in a column having common letters do not differ significantly at 5% level of significance.
37
RESULTS
7 Grain
Straw
6
-1
Yield (t ha )
5
4
3
2
1
0 T1
T2
T3
Nutrients Fig. 4.2 Effect of different nutrients level on grain and straw yield Legend: T 1 = S 43 + K 25
T 3 = S 32 + K 38
T 2 = K 38
T 4 = K 50
38
T4
RESULTS
4.3 Interaction effect of submergence level and nutrients on yield and yield Contributing characters of Binadhan-8 4.3.1 Plant height It is evident from Table 4.5 that the interaction between submergence level and nutrients at harvest had significant effect on plant height (Table 4.5). The highest plant height (108.7 cm) was observed with continuous flooding, S 32 + K 38 (W 1 T 3 ) which was statistically similar with W 1 T 1 , W 1 T 3 and W 1 T 4 . The lowest plant height (96.89cm) was observed in flooding for 10 days, K 38 (W 2 T 2) . Table 4.5: Interaction effect of submergence level and nutrients on plant height (cm) of rice cv. Binadhan-8) Submergence T1 level x nutrients W1 107.20a
T2
T3
T4
Mean
103.6 b
108.7 a
107.8 a
106.83
W2
98.37 fgh
96.89 h
100.4 cdef
97.47 gh
98.28
W3
98.87 fgh
99.07 efg
101.3 cd
99.13 efg
99.59
W4
101.0 cde
97.87 gh
102.3 bc
99.27 defg
100.11
W5
101.1 cde
100.4 cdef
101.4 cd
101.1 cde
101.00
102.82
100.95
Mean
101.31
99.57
101.16
LSD 0.05 : 1.89 Values under interaction treatment having same letter do not differ significantly at 5% level of probability. W1 W2 W3 W4 W5
= continuous flooding, = submergence of field for 10 days (15 DAT) = submergence of field for 20 days (15 DAT) = submergence of field for 30 days (15 DAT) = submergence of field for 40 days (15 DAT)
T 1 = S 43 + K 25 T 2 = K 38
T 3 = S 32 + K 38 T 4 = K 50
39
RESULTS
4.3.2 Panicle length (cm) The experimental results showed that the interaction effect of submergence level and nutrients was significant on panicle length (Table 4.6). However, statistically the longest panicle (28.99 cm) was obtained from continuous flooding, S 32 + K 38 (W 1 T 3 ) whereas the shortest panicle was (25.7 cm) obtained from submergence of field for 10 days, K 38 (W 2 T 2) . Table 4.6: Interaction effect of level of submergence and nutrients on panicle length (cm) of rice (cv. Binadhan-8) Submergence level x nutrients
T1
T2
T3
T4
Mean
W1
28.39 b
27.97 c
28.99 a
28.31 b
28.42
W2
25.27 h
25.07 h
25.77 f
25.10 h
25.30
W3
25.39 gh
25.21 h
25.40 gh
25.22 h
25.31
W4
26.41d
25.63 fg
26.41 d
25.92 ef
26.09
W5
26.37 d
26.19 de
26.43 d
26.23 de
26.31
Mean
26.37
26.01
26.60
26.16
26.28
LSD 0.05 : 0.325 Values under interaction treatment having same letter do not differ significantly at 5% level of probability. W1 W2 W3 W4 W5
= continuous flooding, = submergence of field for 10 days (15 DAT) = submergence of field for 20 days (15 DAT) = submergence of field for 30 days (15 DAT) = submergence of field for 40 days (15 DAT)
T 1 = S 43 + K 25 T 2 = K 38
T 3 = S 32 + K 38 T 4 = K 50
40
RESULTS
4.3.3 Number of Plants hill-1 The interaction effect of submergence level and nutrients for number of Plants hill-1 was also significant (Table 4.7). Results revealed that the height number of plants hill-1 (21.53) was obtained from continuous flooding, S 32 + K 38 (W 1 T 3 ).The lowest number of plants hill-1 (12.00) was observed in continuous flooding K 38 (W 1 T 2 ). Table 4.7: Interaction effect of level of submergence and nutrients on plants hill-1 Of rice (Binadhan-8) Submergence T1 level x nutrients W1 14.73 bc W2 12.33 fg W3 13.20 cdefg W4 12.80 defg W5 14.20 bcd Mean 13.45 LSD 0.05 : 1.41
T2 12.00 g 12.00 g 12.27 fg 12.47 efg 12.40 fg 12.23
T3
T4
21.53 a 13.00 defg 13.60 bcdefg 14.07 bcde 15.00 b 15.44
13.00 defg 12.07 g 12.47 efg 12.67 defg 13.80 bcdef 12.80
Mean 15.32 12.35 12.89 13.00 13.85 13.48
Values under interaction treatment having same letter do not differ significantly at 5% level of probability. W 1 = continuous flooding, W 2 = submergence of field for 10 days (15 DAT) W 3 = submergence of field for 20 days (15 DAT) W 4 = submergence of field for 30 days (15 DAT) W 5 = submergence of field for 40 days (15 DAT) T 1 = S 43 + K 25 T 2 = K 38
T 3 = S 32 + K 38 T 4 = K 50
4.3.4 1000-grain weight (g) Results presented in the Table 4.8 showed that the interaction effect between submergence level and nutrients for 1000-grain weight (g) was statistically significant. The highest 1000-seed weight (25.43g) was observed in continuous flooding, S 32 + K 38 (W 1 T 3 ) and the lowest (21.89g) were observed in submergence of field for 10 days, K 38 (W 2 T 2) .
41
RESULTS
Table 4.8: Interaction effect of level of submergence and nutrients on 1000 grain Weight (g) of rice cv. Binadhan-8 Submergence T1 T2 T3 T4 Mean level x nutrients W1 22.27 fgh 22.50 efgh 25.43 a 23.40 cdefg 23.40 W2
24.65 abcd
21.89 h
24.87 abc
23.68 bcdef
23.77
W3
23.18 defgh
22.10 gh
22.65 efgh 23.57 cdefg
22.88
W4
24.67 abc
23.48 cdefg 22.67 efgh 23.48 cdefg
23.58
W5
24.62 abcd
25.05ab
23.77bcde
22.17 gh
23.90
Mean
23.88
23.00
23.88
23.26
23.51
LSD 0.05 : 1.27 Values under interaction treatment having same letter do not differ significantly at 5% level of probability. 4.3.5 Grain yield It is evident from Table 4.9 that the interaction effect between submergence level and nutrients in relation to grain yield was statistically significant .The highest grain yield (5.140t ha-1) observed in continuous flooding, S 32 + K 38 (W 1 T 3 ) and the lowest (3.480t ha-1) was observed in submergence of field for 10 days, K 38 (W 2 T 2) . Table 4.9.Interaction effect of submergence level and nutrients on grain yield (t ha-1) of rice cv. Binadhan-8 Submergence level x nutrients W1 W2 W3 W4 W5 Mean LSD 0.05 : 0.258
T1
T2
5.063 ab 4.080 ijk 4.320 ghi 4.707 cdef 4.510 fgh 4.54
4.320 ghi 3.480 l 3.927 k 3.960 jk 4.420 fgh 4.02
T3
T4
5.140 a 4.840 bcde 4.580 efg 3.600 l 4.657 def 4.223 hij 4.870 abcd 4.220 hij 4.970 abc 4.487 fgh 4.84 4.27
Mean 4.84 3.94 4.28 4.44 4.60 4.42
Values under interaction treatment having same letter do not differ significantly at 5% level of probability.
42
RESULTS
4.3.6 Straw yield The interaction effect between submergence level and nutrients in relation to straw production was also significant (Table 4.10). The highest straw yield (6.820 t ha-1) observed in continuous flooding, S 32 + K 38 (W 1 T 3 ) and the lowest (4.730 t ha1)
were observed in submergence of field for 10 days, K 38 (W 2 T 2) .
Table 4.10: Interaction effect of submergence level and nutrients on straw yield (t ha-1) of rice cv. Binadhan-8 Submergence T1 T2 T3 T4 Mean level x nutrients W1 W2 W3 W4 W5 Mean
6.433 b 6.270 bcd 6.820 a 6.340 bc 5.170 ijk 4.730 l 5.697 fgh 5.023 jkl 5.357 hij 4.890 kl 5.427 hi 5.023 jkl 6.010 cdef 5.050 jkl 6.200 bcde 5.900 defg 6.120 bcde 5.610 gh 6.080 bcde 5.860 efg 5.82 5.31 6.04 5.63
6.47 5.16 5.17 5.79 5.92 5.70
LSD 0.05 : 0.342 Values under interaction treatment having same letter do not differ significantly at 5% level of probability. W1 W2 W3 W4 W5
= continuous flooding, = submergence of field for 10 days (15 DAT) = submergence of field for 20 days (15 DAT) = submergence of field for 30 days (15 DAT) = submergence of field for 40 days (15 DAT)
T 1 = S 43 + K 25 T 2 = K 38
T 3 = S 32 + K 38 T 4 = K 50
4.3.7 Biological yield With regard to the conclusions of the result interaction of submergence level and nutrients significantly influenced the biological yield (Table 4.11). The highest biological yield (11.96 t ha-1) was recorded from continuous flooding, S 32 + K 38 (W 1 T 3 )and the lowest biological yield (8.210 t ha-1) was observed in submergence of field for 10 days , K 38 (W 2 T 2) . 43
RESULTS
Table 4.11: Interaction effect of submergence level and nutrients on biological yield (t ha-1) of rice cv. Binadhan-8 Submergence level x nutrients W1 W2 W3 W4 W5 Mean
T1
T2
T3
T4
Mean
11.51 b 9.250 h 9.679 g 10.72 de 10.64 de 10.36
10.59 e 8.210 j 8.817 i 9.010 hi 10.03 fg 9.33
11.96 a 10.28 ef 10.08 fg 11.07 cd 11.05 cd 10.89
11.18 bc 8.623 i 9.247 h 10.12 f 10.35 ef 9.90
11.31 9.09 9.46 10.23 10.52 10.12
LSD 0.05 : 0.398 Values under interaction treatment having same letter do not differ significantly at 5% level of probability. W1 = continuous flooding, W2 = submergence of field for 10 days (15 DAT) W3 = submergence of field for 20 days (15 DAT) W4 = submergence of field for 30 days (15 DAT) W5 = submergence of field for 40 days (15 DAT) T 1 = S 43 + K 25 T 2 = K 38
T 3 = S 32 + K 38 T 4 = K 50
4.3.8 Harvest index (%) The interaction effect between submergence level and nutrients in relation to HI was also statistically significant (Table 4.12). The highest HI (46.18%) was observed in submergence of field for 20 days, S 32 + K 38 kg ha-1(W 3 T 3 ). The lowest HI (40.79%) was observed in continuous flooding K 38 (W 1 T 2 ).
44
RESULTS
Table 4.12: Interaction effect of submergence level and nutrients on harvest Index (%) of rice (cv. Binadhan-8) Submergence T1 T2 T3 T4 Mean level x nutrients W1 43.96 bcde 40.79 g 42.96 cdef 43.26 cdef 42.74 W2 44.10 abcde 42.39 efg 44.60abcd 41.74 fg 43.21 W3 44.64 abc 44.53 abcde 46.18 a 45.68 ab 45.26 W4 43.88 bcde 43.97 bcde 44.02 bcde 41.74 fg 43.40 W5 42.42 defg 44.05 abcde 45.04 abc 43.36 cdef 43.72 Mean 43.80 43.15 44.56 43.16 43.67 LSD 0.05 : 1.85 Values under interaction treatment having same letter do not differ significantly at 5% level of probability. W1 = continuous flooding, W2 = submergence of field for 10 days (15 DAT) W3 = submergence of field for 20 days (15 DAT) W4 = submergence of field for 30 days (15 DAT) W5 = submergence of field for 40 days (15 DAT) T1 T2 T3 T4
= S 43 + K 25 = K 38 = S 32 + K 38 = K 50
45
RESULTS
6 T1
T2
T3
T4
4
3
2
1
0 W1
W2
W3
W4
W5
Interaction effect of submergence level and nutrients
Fig. 4.3 Interaction effect of submergence level and nutrients on grain yield 8
T1
T2
T3
T4
7
6
Straw yield (t ha-1)
Grain yield (t ha-1)
5
5
4
3
2
1
0 W1
W2
W3
W4
W5
Interaction effect of submergence level and nutrients
Fig. 4.4 Interaction effect of submergence level and nutrients on straw yield
46
RESULTS
4.4. Effects on Sulphur uptake by rice (Binadhan-8) 4.4.1.1 Effect of submergence S uptake by grain It is evident from Table 4.13 that the effect of submergence on grain yield (kg ha-1) was statistically significant (Fig.7).The highest grain yield (8.137 kg ha-1) was observed in continuous flooding (W 1 ) where the lowest (6.400 kg ha-1) was observed in flooding for 10 days (W 2 ).Result revealed that grain yield at W 4 and W 5 were statistically similar. 4.4.1.2 Effect of submergence S uptake by straw Straw yield was significantly affected by submergence (Table4.13 and fig.7). The highest straw yield (11.47 kg ha-1) was observed in continuous flooding (W 1 ) and the lowest (8.622 kg ha-1) was recorded in submergence of field for 20 days (W 3 ). Reduced straw yield under salinity condition might be due to inhibited photosynthesis under salinity stress that causes less amount of nutrient uptake by the plant. 4.4.1.3 Effect of submergence total S uptake The effect of submergence on total S uptake (kg ha-1) was statistically significant (Table-4.13, and Fig.7). Result revealed that total S statistically similar. The highest total S
uptake at W 4 and W 5 are
uptake (19.60kg ha-1) was observed in
continuous flooding (W 1 ) where the lowest (15.15 kg ha-1) was observed in submergence for 10 days (W 2 ).
47
RESULTS
Table 4.13: Mean effect of submergence level on S uptake by rice (cv. Binadhan-8) Submergence W 1 :continuous Flooding W 2 : flooding for 10days (15 DAT) W 3 : flooding for 20 days (15 DAT) W 4 : flooding for 30 days(15 DAT) W 5 : flooding for 40 days(15 DAT) LSD 0.05
Grain 8.137a
S uptake (kg ha-1) Straw Total 11.47a 19.60 a
6.400 d
8.752 c
15.15c
6.838 c
8.622 c
15.46 c
7.653 b
10.43 b
18.09b
7.956 ab
10.68 b
18.65b
0.329
0.686
0.587
Values in a column having common letters do not differ significantly at 5% level of significance. .
4.4.1.4 Effect of nutrients S uptake by grain The number of grains was markedly affected by sulphur treatment. Nutrients had significant effect on grain yield (Table 4.14). The highest grain yield (8.213 kg ha-1) was obtained from S 32 + K 38 (T 3) and the lowest grain yield (6.555 kg ha-1) was found in K 38 (T 2 ). 4.4.1.5 Effect of nutrients S uptake by straw Results presented in the Table 4.14 showed that Nutrients were significant in terms of straw yield .The highest straw yield (10.82 kg ha-1) was observed from S 32 + K 38 (T 3 ) and the lowest straw yield (8.920 kg ha-1) was produced K 38 (T 2 ). Result showed that S uptake by straw at T 1 and T 3 were statistically similar. 4.4.1.6 Effect of nutrients total S uptake The total S uptake was drastically reduced in Binadhan-8 (salt-tolerant) rice varieties under salt stress condition .Salinity caused significant reductions in total S uptake by Binadhan-8 (salt-tolerant) .Nutrients had significant effect on total S uptake (Table 4.14). The highest total S uptake (19.03 kg ha-1) was obtained from S 32 + K 38 (T 3 ) and the lowest grain yield (15.48 kg ha-1) was found in K 38 (T 2 ).
48
RESULTS
Table 4.14: Mean effect of nutrients on S uptake by rice (Binadhan-8) S uptake (kg ha-1) Grain Straw Total T 1 (S 43 + K 25 ) 7.865 b 10.52 a 18.38 a T 2 (K 38 ) 6.555 d 8.920 c 15.48 c T 3 ( S 32 + K 38 ) 8.213 a 10.82 a 19.03 a T 4 (K 50 ) 6.954 c 9.708 b 16.67 b LSD 0.05 0.278 0.420 0.715 Values in a column having common letters do not differ significantly at 5% level of significance. . Nutrients
4.4.1.7 Interaction effect of submergence and nutrients S uptake by grain With regard to the conclusions of the result the interaction effect between submergence and nutrients in relation to grain yield was statistically significant (Table 4.15). The highest grain yield (9.913) kg ha-1 observed in continuous flooding, S 32 + K 38 (W 1 T 3 ) and the lowest (5.190 kg ha-1) was observed in submergence of field for 10 days, K 38 (W 2 T 2) . 4.4.1.8 Interaction effect of submergence and nutrients S uptake by straw It is evident from Table 4.15 that the interaction effect between submergence and nutrients in relation to straw production was also significant (Table 4.15). The highest straw yield (14.32 kg ha-1) observed in continuous flooding, S 32 + K 38 (W 1 T 3 ) and the lowest (7.287 kg ha-1) were observed in submergence of field for 10 days, K 38 (W 2 T 2) .
4.4.1.9 Interaction effect of submergence and nutrients total S uptake The interaction effect between submergence and nutrients in relation to total S uptake was statistically significant (Table 4.15). The highest total S uptake (24.24 kg ha-1) observed in continuous flooding, S 32 + K 38 (W 1 T 3 ) and the lowest (12.47 kg ha-1) was observed in submergence of field for 10 days, K 38 (W 2 T 2) .
49
RESULTS
Table 4.15: Interaction effect of submergence level and nutrient management on S uptake by rice cv. Binadhan-8 Submergence level x nutrients W1 W2 W3 W4 W5
T1
Grain T2 T3
T4
T1
8.61b
6.88gh
9.91a
7.14 fg
6.89gh
5.19j
8.05bcd
5.47j
7.34efg
6.10 i
6.94gh
8.34bc
6.28hi
8.28bc 7.70cdef 11.27bc
T2
Straw
T3
T4
17.00ef
24.24a
16.99ef
15.94fg
12.47j
18.42bcde
13.77 ij
8.707hij
16.80ef
14.01hij
8.27ijk 10.72bcde 11.48b
19.61bc
14.56 ghi 19.00 bcd 19.18 bcd
19.36bcd
19.35 bcd 18.16 cde 17.74 de
11.57b 10.12def 9.04ghi
7.28k
6.97gh 9.47 fgh 7.893 jk
T3
T4
T1
T2
14.32a
9.85 efg
20.18b
10.37cdef
8.30ijk
8.413 ij
8.14bcd 8.31bc 7.88cde 7.48defg 11.22bc 11.03bcd 10.28cdef 10.20cdef
LSD 0.05
0.617
0.940
The values having common letters do not differ significantly at 5% level of significance. W1 = continuous flooding, W2 = submergence of field for 10 days (15 DAT) W3 = submergence of field for 20 days (15 DAT) W4 = submergence of field for 30 days (15 DAT) W5 = submergence of field for 40 days (15 DAT) T 1 = S 43 + K 25 T 2 = K 38
Total
T 3 = S 32 + K 38 T 4 = K 50
50
15.34fghi 15.68fgh
1.60
RESULTS
4.4.2 Effects on potassium uptake by rice (Binadhan-8) 4.4.2.1 Effect of submergence K uptake by grain With regard to the conclusions of the result the effect of submergence on grain yield (kg ha-1) was statistically significant (Table-4.16). The highest grain yield (26.20 kg ha-1) was observed in continuous flooding (W 1 ) where the lowest (19.08 kg ha-1) was observed in submergence of field for 10 days (W 2 ). Result revealed that grain yield at W 3 and W 4 were statistically similar. Reduced grain yield under salinity condition might be due to the production of lower number of grains panicle-1. 4.4.2.2 Effect of submergence K uptake by straw Straw yield was significantly affected by submergence (Table 4.16). The highest straw yield (127.50 kg ha-1) was observed in continuous flooding (W 1 ) and the lowest (89.37 kg ha-1) was recorded in submergence of field for 10 days (W 2 ). Reduced straw yield under salinity condition might be due to inhibited photosynthesis under salinity stress that causes less amount of nutrient uptake by the plant. 4.4.2.3 Effect of submergence total K uptake The effect of submergence on total K uptake (kg ha-1) was statistically significant (Table 4.16). The highest total K uptake (153.7 kg ha-1) was observed in continuous flooding (W 1 ) where the lowest (108.50 kg ha-1) was observed in submergence of field for 10 days (W 2 ). Result revealed that grain yield at W 3 and W 4 were statistically similar. Reduced total K uptake under salinity condition might be due to the production of lower number of grains panicle-1.
51
RESULTS
Table 4.16: Mean effect of submergence level on K uptake by rice (cv. Binadhan-8) Level of submergence
K uptake (kg ha-1) Straw 127.50 a
Grain 26.20 a
Total 153.70 a
W 1 : Continuous flooding W 2 : flooding for 19.08 d 89.37 c 108.50 d 10 day (15 DAT) W 3 : flooding for 20 22.21 c 95.59 c 117.80 c days(15 DAT) W 4 : flooding for 22.60 c 93.78 c 116.40 c 30 days(15 DAT) W 5 : flooding for 24.12 b 117.40 b 141.50 b 40 days(15 DAT) LSD 0.05 0.741 8.31 7.10 Values in a column having common letters do not differ significantly at 5% level of significance. .
4.4.2.4 Effect of nutrients K uptake by grain Nutrients had significant effect on grain yield (Table 4.17). The highest grain yield (25.90 kg ha-1) was obtained from S 32 + K 38 (T 3) and the lowest grain yield (20.86 kg ha-1) was found in K 50 (T 4 ). The results in Table 4.17 indicated that the K uptake by grain of Binadhan-8 varied significantly by different treatments. 4.4.2.5 Effect of nutrients K uptake by straw The results in Table 4.17 indicated that the K uptake by straw of Binadhan-8 varied significantly by different treatments. Nutrients had significant in terms of straw yield. The highest straw yield (117.20 kg ha-1) was observed from K 50 (T 4 ).and the lowest straw yield (88.26 kg ha-1) was produced in K 38 (T 2 ).
4.4.2.6 Effect of nutrients total K uptake
The total K uptake by grain and straw was also significantly affected by the different treatments (Table 4.17) and the total K uptake by Binadhan-8 varied from 138.0 to 109.7 kg ha-1. Nutrients had significant effect on total K uptake (Table 4.17). The highest total K uptake (138.0 kg ha-1) was obtained from (T 4 ) and the lowest total K uptake (109.7 kg ha-1) was found in K 38 (T 2 ).
52
RESULTS
Table 4.17.Mean effect of nutrients on K uptake by rice cv. Binadhan-8 Nutrients T 1 (S 43 + K 25 ) T 2 (K 38 ) T 3 ( S 32 + K 38 ) T 4 (K 50 ) LSD 0.05
K uptake (kg ha-1) Straw 103.20 c 88.26 d 110.20 b 117.20 a 4.87
Grain 23.20 b 21.40 c 25.90 a 20.86 c 0.712
Total 126.40 b 109.70 c 136.10 a 138.00 a 4.56
Values in a column having common letters do not differ significantly at 5% level of significance.
4.4.2.7 Interaction effect of submergence and nutrients K uptake by grain Results presented in the Table 4.18 showed that the interaction effect between submergence and nutrients in relation to grain yield was statistically significant. The highest grain yield (30.92kg ha-1 observed in continuous flooding, S 32 + K 38 (W 1 T 3 ) and the lowest (14.38 kg ha-1) was observed in submergence of field for 10 days, K 38 (W 2 T 2) .
4.4.2.8 Interaction effect of submergence and nutrients K uptake by straw It is evident from Table 4.18 that the interaction effect between submergence and nutrients in relation to straw production was also significant (Table 4.18). The highest straw yield (163.20 kg ha-1) observed in continuous flooding, S 32 + K 38 (W 1 T 3 ) and the lowest (51.09 kg ha-1) were observed in submergence of field for 10 days, K 38 (W 2 T 2) . 4.4.2.9 Interaction effect of submergence and nutrients total K uptake The interaction effect between submergence and nutrients in relation to total K uptake was statistically significant (Table 4.18). The highest total K uptake (194.2 kg ha-1 observed in continuous flooding, S 32 + K 38 (W 1 T 3 ) and the lowest (65.47 kg ha-1) were observed in submergence of field for 10 days, K 38 (W 2 T 2) .
53
RESULTS
Table 4.18: Interaction effect of submergence level and nutrients on K uptake by rice cv. Binadhan-8 Submergence level x nutrients W1 W2 W3 W4 W5 LSD 0.05
Grain T1 24.61cd 23.49de 22.47efgh 23.19def 22.26efgh
T2
Straw T3
T4
22.98defg 30.92a 26.31b 14.38k 20.77hi 17.67j 21.21ghi 26.64b 18.51j 22.54efgh 24.52cd 20.15i 25.91bc 26.67b 21.66fghi 1.59
T1
T2
Total T3
= continuous flooding, = submergence of field for 10 days (15 DAT) = submergence of field for 20 days (15 DAT) = submergence of field for 30 days (15 DAT) = submergence of field for 40 days (15 DAT)
T 1 = S 43 + K 25 T 2 = K 38
T1
T2
T3
T4
83.46gh 128.5bc 163.2a 134.7b 108.1fg 151.5bc 194.2a 161.0b 96.82ef 51.09j 99.85de 109.7d 120.3de 65.47i 120.6de 127.4d 121.0c 100.3de 75.97h 85.13fgh 143.4c 121.5de 102.6g 103.6fg 90.80efg 64.92i 86.75fgh 132.7bc 114.0ef 87.46h 111.3efg 152.8bc 124.1bc 96.49ef 125.2bc 123.6bc 146.4c 122.4de 151.9bc 145.3c 10.90 10.21
The values having common letters do not differ significantly at 5% level of significance. W1 W2 W3 W4 W5
T4
T 3 = S 32 + K 38 T 4 = K 50
54
DISCUSSION
CHAPTER 5 DISCUSSION Rice is one of the most widely grown crops in coastal areas (Akbar and Yabuno, 1972). Binadhan-8, a salt tolerant boro rice variety was tested in saline area to see the impacts of prolonged flooding with fresh water (in the form of irrigation) and additional application of two nutrients K and S on its yield performance. In the present study, five submergence levels viz. W 1 : continuous flooding, W 2 : submergence of field for 10 days (15 DAT), W 3 : submergence of field for 20 days (15 DAT), W 4 : submergence of field for 30 days (15 DAT), W 5 : submergence of field for 40 days (15 DAT) and four nutrients rates viz.T 1 : S 43 + K 25 , T 2 : K 38 , T 3 : S 32 + K 38 , T 4 : K 50 were imposed on Boro rice cv. Binadhan-8. It was observed that the different levels of flooding had significant effect on the yield and yield components. The most yield and yield components were increased with increasing flooding duration, on the other hand it decreased due to short duration flooding. Rice yield usually decreases at salt stress, but in this study it was increased due to application of fresh water in different duration. Certain depth of irrigation water is kept in the field for growing successful rice crop. This practice simultaneously helps in leaching of soluble salt consequently reducing soil salinity (SRDI, 2010). If sufficient irrigation water of good quality is available, introduction of rice crop is possible in saline area resulting in the additional production of grain yield. Binadhan-8 was responded significantly due to application of different nutrients (K and S) over the normal recommended rate. Combined application of these two nutrients gave the better results than using K alone. Beneficial effects of K and S (as gypsum) on crop in saline soils were reported by many researchers. Potassium application alleviated the stress condition and significantly improved dry matter yield and yield components in rice (Ebrahimi et al., 2012). The number of tillers increased significantly (P
