NPK-fertilization effect on drought overcome of sunflower (Hellianthus annuus L.)

Field Crop Production Original scientific paper NPK-fertilization effect on drought overcome of sunflower (Hellianthus annuus L.) Velichka Koteva1, M...
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Field Crop Production Original scientific paper

NPK-fertilization effect on drought overcome of sunflower (Hellianthus annuus L.) Velichka Koteva1, Marina Marcheva2 1 2

Institute of agriculture – Industrialna 1, Karnobat 8400, Bulgaria¸email: [email protected] Institute of Plant Genetic Resources “K. Malkov” – Drujba 2, Sadovo 4122, Bulgaria

Abstract The sunflower is one of the most important crops in the Bulgarian agriculture with 30 – 40 % of the annually cultivated areas in the country. Insufficient amounts of rainfalls during the vegetation and high air temperature at flowering phase are crucial for nutrition of sunflower plants and correspondingly for the formation of grain yield. The present study aims at investigation of the mineral fertilization effect on the drought overcome by sunflower (Helianthus annuus L.) cultivated for 45 years in long term stationary fertilizing trial (maizewheat-sunflower-barley rotation). Four fertilizing levels of NPK-fertilization (Т0 =N0 P0 K0; Т1= N50 P20 K20; Т2= N100P60K60; Т3=N150 P80 K80) were applied. Sunflower grain yield and weather data (precipitation and air-temperatures) for the period 1963 – 2007 was shown. In general, applied fertilization effects on yields and alleviation of drought stress were low. The sustainable growing of sunflower on Pellic vertisols in South East Bulgaria in dry years can be achieved without mineral fertilizing. However, for the other field crops are needed moderate fertilization. Key words: sunflower, grain yield, fertilization, drought, long term stationary trial.

Introduction The sunflower is main oil crop for Bulgaria. Grain is meant to satisfy the oil and biodiesel production. Part of its production is exported to EU and Asia. The sunflower consist 30 – 40 % of the field crops rotation with 0.6 – 0.7 millions ha cultivated every year (http://www.mzh.government.bg). It presents important part of the total production and economical gain for the farmers and leaseholders. The yield is essential for the sustainable development of the Bulgarian agriculture. The sunflower yield depends on the genetic potential of the hybrid and the environmental conditions (Radevska, 2004). Local Bulgarian and foreign hybrids with high productive potential are grown in Bulgaria. Modern intensive cultivation practices are used. Treatment with moderate N-P-K fertilizers ensures good soil chemical composition (Angelova, 2001; Ilkov, 1984; Saldjiev 2004). In Bulgaria the sunflower is grown on soils with good potential fertility. Main restrictive factor is the climate (Ivanov and Plamenov, 2002; Nikolov, 1999; Slavov et al., 2005). Problematic environmental conditions are the water deficit during the whole vegetation period and the high air temperature at flowering phase (Koteva, 1992). As evidences for that can be point the extreme low ield in the very dry year of 2007 (940 kg/ha) and the one in the favorable conditions of 2008 (1770 kg/ha). Global warming and decrease of the rainfalls in most of the geographical regions have negative effect on the crops‘ productivity (Dekov, 1997; Draganov, 1956; Parry, 1990). Short or longer droughts occur more frequently in the recent years (Koteva, 1992). Severe drought during all the vegetation period of the sunflower was manifested in 1983 and 2007. Practically every second year the sunflower suffers from spring and summer droughts (Stanev et al., 1995).

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The sunflower nutrition is a complicated physiological process. The mineral fertilizing and the natural soil supply of mobile nitrogen (N), phosphorus (P) and potassium (K) are of primary importance for it. Insufficient amounts of rainfalls and high air temperature during the vegetation in many years are crucial for nutrition of sunflower plants and correspondingly for the formation of grain yield. The considerable role of the mineral fertilizing on the drought overcome has been investigated by several Bulgarian (Angelova et al., 2003; Ilkov, 1984; Radomirov, 1937) and foreign researchers (Parry, 1990). Stationary and long-term experiments are suitable for testing fertilization on field crops status including sunflower. Aim of this study was testing fertilization effect on the drought overcome by sunflower (Helianthus annuus L.) cultivated for 45 years in long term stationary fertilizing trial.

Material and methods The experiment was conducted in the stationary fertilizing trial (maize – wheat - sunflower barley rotation) maintained since 1963 in the experimental field of the Institute of agriculture – Karnobat (South East Bulgaria) on Pellic vertisols. The cultivation practices are according the established traditional techniques for the corresponding varieties and hybrids. Observations and investigations were made on the sunflower variety Peredovik and hybrid Albena. Fertilizing levels of N, P and K are determined provisionally as ―low‖ –T1, ―moderate‖ – T2, and ―high‖ - Т3. Comparisons are to the non-fertilizing control – T0. The application rates are accordingly the biological requirements of each crop. They were augmented three times in the first 20 years. In the last 25 years the fertilizing levels remain unchanged - „low‖ by N50 P20 K20 (Т1); ―moderate‖ - N100 P60 K60 (Т2); „high‖ - N150 P80 K80 (Т3); and „non-fertilized‖- N0 P0 K0 (Т0). Hereafter are present the analyses of the results from the variants Т1 and Т2 which fertilizing is close to the one used in the agricultural practices in Bulgaria. The non-fertilized check T0 is used as control. Data for grain yield (kg/ha at 14 % humidity) of sunflower, cultivated in the crop rotation in the stationary trial during the period 1963 - 2007, are summarized. The rainfall in the vegetatio and the average monthly air temperature in July and August are analyzed. In previous researches has been established medium correlation between those parameters and grain yield (Koteva, 1992). The soil fecundity changes were track out by content of mineral nitrogen (Turin- Kononova method), mobile Р and K (AL-method), total humus (according Turin) and рН in KCl (potentiometrically). Agrochemical analyses were made in samples of the 0 – 60 cm soil layer from each variant in four replicates. The trial was conducted on Pellic vertisols with favorable for the sunflower soil fertility. The humus layer (0–60 cm) is heavy sandy-loamy with moderate content of humus and weak acid reaction. The supply of mineral nitrogen is poor, mobile phosphorus – poor to moderate, mobile potassium – good, main micro-elements (Zn, Cu, Fe, Mn, Mo and B) – moderate to good (Koteva, 1992). The Karnobat region has continental climate with average rainfall 553 mm in the last century. The spring is continuous and cool, summer – hot and dry, autumn – warm and dry and wintermoderate warm and humid. Results and discussion The soil fertility in the stationary trial has been changed by the crops fertilization for 45 years. The results from agrochemical analysis in 1982 – 2007, compared to the one before the trial establishment in 1963 made by Philipov (1976), are present to Table 1.

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It has been found tendency to diminution of total humus, mineral N and mobile P in crop rotation without fertilization (Т0). Unchanged remain the soil reaction and mobile potassium content. In this variant the sunflower is developed in conditions of nitrogen and phosphors deficit but at good potassium supply. Table 1. Soil fertility changes influenced by continuous mineral fertilization in crop rotation in stationary fertilizing field trial. Soil properties and fertilization level: mineral N (mg/1000g), AL-soluble Р2О5 and К2О (mg/100g), humus (%) and pH (1nKCl); A = at start the experiment 1963 (Philipov, 1976) and status in the period 1982-2007 (B = means; C = range of variations) Control* (N0 P0 K0 =Т0) Low (N50 P20 K20=Т1) Moderate (N100P60K60=Т2) A B C A B C A B C N 27.4 25.7-31.4 49.9 44.7-55.1 62.8 51.6-67.2 Р2О5 2–4 3.2 2.6-4.3 2–4 6.3 5.5- 6.9 2–4 13.3 10.5-16.9 К2О 32–35 35.3 34.2-37.0 32–35 40.2 39.8-42.4 32–35 49.0 42.7-51.4 Humus 2. 74 2.74 2.56-2.79 2. 74 2.81 2.79-2.99 2. 74 2.91 2.89-2.97 pHKCl 5.9-6.3 6.4 6.0-7.0 5.9-6.3 6.6 6.5-7.2 5.9–6.3 6.6 6.5-7.2

The low fertilizing levels (Т1) retard the decrease of the total humus and the mobile phosphorous observed in the non-fertilized control. The content of mineral nitrogen and mobile phosphorus is higher but still insufficient for the optimal nutrition of the crop. The moderate level (Т2) ensures good circumstances for balanced nutrition of the sunflower – the content of mineral N and mobile P, while K was sufficiently. The humus content, compared to 1963 amount, marks tendency to increase. In all three variants the soil reaction remains weak acid and creates conditions for mineralization of the organic matter. This ensures additional nutritive substances and ameliorates the nutritive regime of sunflower. The characteristic of the years as suitable for the sunflower is determined by calculation of the security (P %) of rainfall in the vegetation period and average air temperature in July and August. Data are present in Table 2. Table 2. Year characterization during the vegetation period (March - August). Weather characteristics (locality Karnobat) in the period 1963-2007: mean air-temperatures (0С) and precipitation (H-humid, MH-moderate humid, M-moderate, MD-moderate dry, D-Dry, VD-very dry, VHvery hot, W-warm, MV-moderate warm, MC-moderate cool, C-cool) Precipitation Mean air-temperature (NY = number of years) (March-August) July August 0 0 Year mm NY Year С NY Year С NY H 440 - 361 8 VH 25.0 - 22.5 10 VH 24.0 - 22.3 9 MH 352 - 323 8 W 22.3 - 22.1 8 W 22.2 - 21.6 7 M 310 - 252 9 MW 22.0 - 21.4 9 MW 21.5 - 20.7 9 Total 25 Total 27 Total 25 MD 248 - 230 8 M 21.3 - 21.0 10 VH 20.6 - 20.0 11 D 224 - 176 6 MC 20.9 - 20.0 6 W 19.9 - 18.1 7 VD 175 - 160 6 C 19.2 - 11.0 2 MW 16.3 - 15.4 2 Total 20 Total 18 Total 20

The analyses show that in the 45-y period 25 years (55 %) are humid, moderate humid and moderate (Table 2). They can be considered as favorable regarding the soil humidity expressed by rainfall amount. It is well known that at sufficient water supply the nutrition elements, imported by the fertilizers and accumulated in the soil layers has higher coefficient of assimilation. Thus under favorable nutrition regime the sunflower can express its full

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productive potential. The rest 20 years (45%) are moderate dry, dry or very dry. Under similar circumstances the occurred water deficit has negative effect on the growth and development of the crop. It is due not only to the shortage of water but also to the low coefficient of assimilation of fertilizer and soil nutritive substances. The average air temperature in July and August frequently are unfavorable (Table 2). July has been very hot to moderate hot in 60 % of the years and in the rest 40 % - moderate to cool. Every fourth year had very high air temperature in the sunflower flowering phase (July). The climate conditions at grain ripening in August are similar to July – 55 % of the years are very hot to warm and 45 % are moderate to cool. The average yields for 45 years prove that the natural fertility of Pellic vertisols (variant T 0) secure formation of grain yield of 1520 kg/ha (table 3). Amelioration of the soil fecundity and creation of better nutritional regime has been reached by long term fertilization with N-P-K. The low rates of fertilizing (T1) raise the yield by 350 kg/ha while the moderate rates – by 480 kg/ha. Table 3. Grain yield of sunflower, cultivated with different fertilization regimes in dry and favorable years, kg/ ha. Fertilization

Average for 1963-2007

Т0 Т1 Compared to Т0 Т2 Compared to Т0 Compared to Т1

1520 1870 + 350 2000 + 480 + 130

During the period 1963 – 2007 Very dry and dry years Moderate and medium humid (in risk) years (favorable) Average Variation Average Variation 710 450 - 1080 2180 1990 - 2950 780 350 - 1150 2730 1980 - 3060 + 70 + 550 790 270 - 1200 2520 2100 - 3680 + 80 + 340 + 10 - 210

In years with favorable climate conditions and good coefficient of assimilation of the soil and fertilizer nutrition elements in the non-fertilized control (T0) the yield reaches 2180 kg/ha, in the ―low‖ (T1) variant - 2730 kg/ha and in ―moderate‖ (T2) – to 2520 kg/ha (table 3). Very dry and dry years reduce the sunflower productivity to 710 kg/ha in Т0, 780 kg/ha in Т1 and 790 kg/ha in Т2. The yield in both variants with different levels of fertilizing is almost equal to the control T0. No effect of the fertilizing or the soil fecundity has been shown in such conditions. Lower variation of the grain yield is observed at ―low‖ level of fertilization (350 - 1150 kg/ha) than the ―moderate‖ variant T2 (270 - 1200 kg/ha).

Conclusions In South-East Bulgaria every second year in the last 45 was in risky for the sunflower cultivation on Pellic vertisols because of the insufficient rainfalls during the vegetation period and high air temperatures at flowering phase, grain fill and ripening. The sunflower has very low grain yield (710 kg/ha) at natural soil fertility of the Pellic vertisols, in dry years with obvious water deficit. The mineral fertilizing creates better nutritional regime but does not reduce the negative effect of the drought and does not raise the grain yield. The sustainable cultivation of oil sunflower on Pellic vertisols in South East Bulgaria in dry years can be achieved without mineral fertilizing. This requires annually moderate fertilizing of the other species in the crop rotation to ensure soil supply of mineral nitrogen above the average (more then 50 mg/1000 g), and good reserve of mobile phosphorus and potassium (more then 10 mg/100 g and 40 mg/100 g correspondingly).

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References Angelova, M., D. Georgiev, L. Glogova (2003). Investigation of the different correlation between the precipitation and the content of nitrogen, phosphorus and potassium in the sunflowers stalks. Scientific conference, Stara Zagora, vol. 1, Agrarian sciences, part 2, Crop science, pp.103-116. Angelova, M. (2001). Nitrogen fertilization effect on the sunflower yield on pellic vertisols in Northwest Bulgaria, Plant science, vol. 38, pp. 14-21. Dekov, O., (1997), Review of global changes and main trends in agricultural researches, Agricultural science, 1997, vol. 4, pp. 34 - 36. Draganov, Dr., (1956), Characterization of climate inconvenience in South-East Bulgaria. Book of scientific works in agriculture of Institute MA, vol. Х. Ivanov, P., Dr. Plamenov, (2002), Global warming, climate changes and agricultural adaptation. (Review), Research Communications of U.S.B. - Dobrich, , vol. 4, pp. 14 - 21. Ilkov, D., (1984), Mineral and organic farming in the struggle with drought. Soil science and agro chemistry, vol. 2, pp. 9 - 18. Koteva, V., (1992). Changes in some parameters of the soil fertility in leached smolnitza under continuous fertilizing in crop rotation, Dissertation, Sofia, pp. 193. Radevska, M., (2004), Field trial of sunflower hybrids in the climate conditions of Central South Bulgaria, Field Crops Studies, vol. II – 2, pp. 303-308. Radomirov, P., (1937), Drought and artificial fertilizers, Sofia, pp. 110. Saldjiev, Iv. (2004). Effect of fertilization and crop density on the yield from sunflower variety Peredovik. Field Crops Studies, vol. 1, pp. 434 - 438. Slavov, N, V. Georgieva, M. Moteva, (2005). Climate changes in Bulgaria in the last century and negative changes of the natural resources, Scientific reports from Scientific conference, 15 – 19th of May 2005, Sofia, pp. 533 - 538. Stanev, S. M. Kuchukova, S. Lingova, (1995). Climate of Bulgaria, Sofia, pp. 199. Philipov, Hr., (1976), Influence of the systematically fertilizing with increasing levels on the crop‘s productivity, Dissertation, Plovdiv, pp.160. Parry, M. L. (1990). Climate change and World agriculture, London, pp. 230. http://www.mzh.government.bg

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