Acta Sci. Pol., Agricultura 10(2) 2011, 57-73

EFFECTIVENESS OF WEED CONTROL IN MAIZE (Zea mays L.) DEPENDING ON THE DATE AND METHOD OF HERBICIDE APPLICATION Roman Kierzek, Adam Paradowski, Roman Krawczyk Institute of Plant Protection – National Research Institute in Poznań1 Abstract. In years 2006-2009, six experiments were carried out. Their aim was the assessment of the effectiveness of herbicides used for weed control in maize at lower doses and different dates. Herbicides were applied in three variants: (1) twice on weeds at a stage no later than two proper leaves regardless of maize developmental stage, (2) in-leaf operation + on-leaf operation, (3) two on-leaf operations – at the stages of 1-3 and 4-6 maize leaves. In the research, the following active substances were used: acetochlor, dicamba, linuron, florasulam + 2.4-D, fluroxypyr, foramsulfuron + iodosulfuron, nicosulfuron, nicosulfuron + rimsulfuron, and rimsulfuron. Research showed that after the application of lower herbicide doses, there is a possibility to obtain satisfactory herbicidal effect. Limitation of weed number and weed development inhibition made it possible to obtain yields that did not differ significantly from the ones obtained after the operations with standard doses. The best component in the studied herbicide mixtures proved to be the combination of florasulam + 2.4-D. In the case of significant Chenopodium album L. infestation, fluroxypyr should not be used as a mixture component. It was also found that in the conditions of late and uneven weed emergence, the system of two operations with lower herbicide doses limited effectively maize infestation in a longer growth period. Key words: herbicide mixture, lower herbicide dose, maize infestation, pest control, split doses

INTRODUCTION In recent years, in many regions of the country – due to unfavourable weather conditions – low effectiveness of pest control operations in maize growth was noted. Particularly low effectiveness, mostly due to dry soil, was characteristic for in-soil herbicides applied before cultivated plant emergence. Means for on-leaf pest control were applied usually with great delay due to cold. Therefore, on many plantations, mass emergence of secondary infestation was noted [Gołębiowska 2006]. Lack of Corresponding author – Adres do korespondencji: dr Roman Kierzek, Department of Weed Science and Plant Protection Techniques of the Institute of Plant Protection – National Research Institute in Poznań, W. Węgorka 20, 60-318 Poznań, e-mail: [email protected]

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precipitation after maize sowing and long periods of low temperatures decrease herbicide effectiveness in relation to the species that emerge in masses at a latter time [Gołębiowska and Snopczyński 2008]. After the withdrawal of atrazine, the possibilities of chemical maize protection against weeds became limited [Paradowski 2008]. First of all, the number of herbicide mixtures to prepare in containers decreased drastically. Due to the negative effects of the climate and simplifications in agrotechnics, conducting one herbicide operation with the use of one active substance may not guarantee full plantation protection against infestation during the entire growth period [Rola and Rola 1995, Gołębiowska 2006, Gołębiowska and Kaus 2009b]. Such situation creates the necessity to search for new and effective methods of maize weeding and its better protection against secondary infestation. Particular attention should be paid to the improvement of the effectiveness of on-leaf operations, to the need of performing more than one chemical operation [Kierzek and Adamczewski 2008, Paradowski 2008], and also to the use of complex mixtures made by factory or right before the operation in sprayer tank [Skrzypczak et al. 2007, Kierzek and Adamczewski 2008, Snopczyński and Gołębiowska 2008]. Cost of such protection should not undergo significant increase in relation to traditional chemical weed control [Paradowski and Kierzek 2009]. One of the possibilities to obtain better pest control results is the joint application of herbicides with adjuvants [Matysiak et al. 1995, Praczyk and Adamczewski 1996, Woźnica et al. 1997, Skrzypczak et al. 1998, Woźnica and Skrzypczak 1998, Adamczewski and Matysiak 2005, Kierzek and Miklaszewska 2009]. Aim of the research was the assessment of maize weed control with the use of lower herbicide doses and conducting two herbicide operations at different application times. In the experiment, the application of herbicides directly after sowing and in two on-leaf operations was taken into account, at different maize developmental stages. MATERIAL AND METHODS Research was carried out in years 2006-2009 at the Field Experimental Station Institute of Plant Protection – National Research Institute (IPP – NRI) in Winna Góra (two experiments) (52o12’ N; 17o27’ E) and one on each individual farm situated in the fields near Poznań – in Dąbrówka (52o22’ N; 16o44’ E), Lusowo (52o25’ N; 16o41’ E), Nieczajna (52o34’ N; 16o46’ E), and Rawicz (51o36’ N; 16o50’ E). All the experiments were set up as a randomized block design in four replications. Maize was grown for grain or silage. Preparations were applied at three different times: – directly after sowing, – at the 1-3 maize leaf stage, – at the 4-6 maize leaf stage. In one experimental cycle, the application of herbicides was marked by weed development stage. The operations were carried out at the latest during the stage of first true pair leaves, regardless of maize developmental stage. Observations of the effects of weed control were carried out with the use of the visual method, that is through the comparison of plant state and condition on plots treated with herbicides with the control (no treatment). Results were presented in a percentage scale, where 0% was no herbicide effect, and 100% was total weed Acta Sci. Pol.

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destruction. Fresh mass of 100 cobs (calculated as standard grain moisture 14%) and green mass of maize plants were marked. Results underwent statistical evaluation with the use of analysis of variance and the t-Student’s test. Result diversification significance was evaluated at the level of P = 0.05. Biological effect of the application of the following active substances was studied: 2.4-D + florasulam (Mustang 306 SE), acetochlor (Guardian 840 EC or Trophy 768 EC), dicamba (Dicamba 480 SL), linuron (Dispersive Afalon 450 SC), fluroxypyr (Starane 250 EC), foramsulfuron + iodosulfuron (Maister 310 WG), nicosulfuron (Milagro 040 SC), and rimsulfuron (Titus 25 WG). Trade names, active substance content, and the applied doses are presented in Table 1. In the experiments carried out in Dąbrówka, Nieczajna, and Rawicz, to the second on-leaf treatment, adjuvant Atpolan Bio 80 SL was added (methyl ester of rapeseed oil, pH stabilizers). Detailed data concerning the choice of active substances, doses of the particular combinations, and application dates, and also results including herbicide effect in relation to the particular species, plant height, and maize yield are presented in Tables 2-5. During the analyses, the phytotoxic effect of herbicides in relation to maize was also determined. Data concerning weather conditions in the four growth seasons is presented in Figures 1-4 and in Table 6. RESULTS Effects of the chosen maize weed control systems on Chenopodium album L. destruction – experiments carried out in years 2006-2008 Operations were carried out in two systems. In the first system, in-soil treatment was carried out before maize emergence and on-leaf on weeds at the stage of the first couple of proper Ch. album leaves. In the second system, both treatments were carried out at the stage no latter than of two true Ch. album leaves. In neither of the systems, maize developmental stage was not taken into account. Herbicide effect In the part of the experiment that included in-soil and early on-leaf treatment, the average number of Ch. album in the particular years oscillated between 16 and 116 plants per 1 m2, which amounted to 10% to 57% of the population of all weeds (Table 2). In the system of two on-leaf treatments, the number of Ch. album was similar and amounted to analogically 25 to 114 plants per 1 m2, which equalled 17% to 55% of the population. During three years in the in-soil – on-leaf system, the best herbicide effect was obtained after the application of acetochlor/florasulam + 2.4-D combination (89-100% effectiveness), and in the system of two on-leaf treatments, after two times application of florasulam + 2.4-D (98-100%) and the mixture of florasulam + 2.4-D /dicamba (89-99%). In-soil combinations with the participation of linuron demonstrated poor herbicide effect in the first year of the experiment (2006). Very diversified effect was characteristic for on-leaf operations with the use of dicamba, since, depending on the year of the experiment, Ch. album destruction was obtained from 28% up to 100%. The poorest effect was found after its two times application on the same plot and jointly with fluroxypyr. Pure fluroxypyr destroyed the species within the range of 0% to 32%, and with the participation of dicamba from 4% to 78%.

Agricultura 10(2) 2011

Active substance (a.s.) Substancja aktywna (s.a.)

linuron (450 g·dm-3) dicamba (480 g·dm-3) foramsulfuron + iodosulfuron (10 + 300 g·kg-1) nicosulfuron (40 g·dm-3) florasulam + 2.4-D (6.25 + 300 g·dm-3) fluroxypyr (250 g·dm-3) rimsulfuron (25%) acetochlor (768/840 g·dm-3)

Herbicide – Herbicyd

Afalon Dyspersyjny 450 SC Dicamba 480 SL MaisTer 310 WG Milagro 040 SC Mustang 306 SE Starane 250 EC Titus 25 WG Trophy 768 EC/Guardian 840 EC

Table 1. List of herbicides and their doses used in the experiments Tabela 1. Wykaz herbicydów i ich dawek stosowanych w doświadczeniach

900 240 45 + 1.5 60 3.8 + 180 250 15 1920 / 2100

maximum recommended dose maksymalna według zaleceń 675 96 15 + 0.5 20; 40 1.9 + 90 75; 125 7.5 768 / 840

tested lower doses testowane dawki obniżone

Dose, g a.s.·ha-1 – Dawka, g s.a.·ha-1

75 40 33 33; 66 50 30; 50 50 40

Percentage of the recommended maximum dose applied in the experiments Procent zalecanej dawki maksymalnej stosowanej w badaniach %

60 R. Kierzek, A. Paradowski, R. Krawczyk

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Agricultura 10(2) 2011 Dose of a.s. Dawka s.a. g·ha-1

Application time** Termin zabiegu

Ch. album control Zniszczenie Ch. album %

Maize plant height Wysokość roślin kukurydzy m

2007 11.1 21.7 19.2 20.6 22.3 2.85 10.7 18.7 17.1 11.9 21.4 18.7 2.75

2006 – – – – –

– – – – – –

22.3 19.0 16.1 23.5 15.1 3.05

11.6

27.7 21.1 28.3 27.3 3.32

12.6

2008

100 maize cob mass Masa 100 kolb kukurydzy kg

* localization and year of the experiment – miejscowość i rok badań ** application time – termin zabiegu: T0 – in-soil, pre-emergence treatment – doglebowo, przed wschodami kukurydzy, T1 – on-leaf, post-emergence, regardless of maize developmental stage on weeds up to the 2-leaf stage – nalistnie, bez względu na fazę rozwojową kukurydzy, na chwasty do fazy 2 liści, T2 – 10-14 days after T1, regardless of maize developmental stage, on weeds up to the 2-leaf stage – około 10-14 dni po T1, bez względu na fazę rozwojową kukurydzy na chwasty do fazy 2 liści

2006 2007 2008 2006 2007 2008 Two treatment system – in-soil (T0) and on-leaf (T1) – System dwóch zabiegów – doglebowy (T0) i nalistny (T1) Control, plant·m-2 / % in total weed population 53 / 16 / 116 / – – – 1.53 1.70 39% 10% 57% Kontrola, szt.·m-2 / % w ogólnej populacji chwastów Acetochlor/florasulam + 2.4-D 768/1.9 + 90 T0/T1 100 94 89 – 1.93 1.88 Acetochlor/dicamba 768/96 T0/T1 96 68 26 – 2.05 2.28 Linuron/florasulam + 2.4-D 675/1.9 + 90 T0/T1 68 86 96 – 1.88 2.55 Linuron/dicamba 675/96 T0/T1 67 96 89 – 2.10 2.43 LSD0.05 – NIR0,05 Two on-leaf treatment system – T1 and T2 – System dwóch zabiegów nalistnych – T1 i T2 Control, plant·m-2 / % in total weed population 90 / 25 / 114 / – – – 1.54 1.30 Kontrola, szt.·m-2 / % w ogólnej populacji chwastów 46% 17% 55% Florasulam + 2.4-D/florasulam + 2.4-D 1.9 + 90/1.9 + 90 T1/T2 100 99 98 – 1.83 1.94 Dicamba/dicamba 96/96 T1/T2 75 100 28 – 1.70 1.41 Fluroxypyr/fluroxypyr 75/75 T1/T2 13 0 32 – 1.76 1.51 Florasulam + 2.4-D/dicamba 1.9 + 90/96 T1/T2 96 99 89 – 2.30 2.02 Dicamba/fluroxypyr 96/75 T1/T2 4 78 43 – 2.07 1.44 LSD0.05 – NIR0,05

Combination – Kombinacja

Table 2. Effect of weed control systems on Chenopodium album control and maize plant height and cob mass (Winna Góra 2006, Lusowo 2007, Dabrówka 2008)* Tabela 2. Wpływ systemów odchwaszczania na zniszczenie Chenopodium album oraz na wysokość roślin i masę kolb kukurydzy (Winna Góra 2006 r., Lusowo 2007 r., Dabrówka 2008 r.)*

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Application time* Termin zabiegu

Weed control effectiveness Skuteczność zniszczenia chwastów % Green mass yield Plon zielonej masy t·ha-1

24.5 25.6 23.3 23.9 25.5 25.6 24.1 24.7 4.92

25.1 24.5 22.4 23.4

20.1

100 maize cob mass Masa 100 kolb kukurydzy kg

* application time – termin zabiegu: T0 – in-soil, pre-emergence treatment – doglebowo, przed wschodami kukurydzy, T1 – on-leaf, post emergence, at the 1-3 maize leaf stage – nalistnie, w fazie 1-3 liści kukurydzy, T2 – on-leaf, post emergence, at the 4-6 maize leaf stage – nalistnie, w fazie 4-6 liści kukurydzy ** herbicide with the addition of adjuvant Atpolan Bio80 SL at the dose of 1.0 dm3·ha-1 – herbicyd z dodatkiem adiuwanta Atpolan Bio 80 SL w dawce 1,0 dm3·ha-1 ECHCG – Echinochloa crus-galli, CHEAL – Chenopodium album, POLsp. – Polygonum species (P. convolvulus + P. nodosum + P. aviculare)

ECHCG CHEAL POLsp. Two treatment system – in-soil (T0) and on-leaf (T1) – System dwóch zabiegów – doglebowy (T0) i nalistny (T2) Control, plant·m-2 / % in total weed population 120 / 20 / 20 / – – 82.4 Kontrola, szt.·m-2 / % w ogólnej populacji chwastów 67% 12% 12% Acetochlor/nicosulfuron** 768/40 T0/T2 100 100 99 105.3 Acetochlor/nicosulfuron** 768/20 T0/T2 100 199 99 97.1 Acetochlor/rimsulfuron** 768/7.5 T0/T2 100 99 97 91.0 Acetochlor/foramsulfuron + iodosulfuron** 768/15 + 0.5 T0/T2 99 98 88 90.1 Two on-leaf treatment system T1 and T2 – System dwóch zabiegów nalistnych – T1 i T2 Florasulam + 2.4-D/nicosulfuron** 3.8 + 180/40 T1/T2 100 100 97 105.5 Florasulam + 2.4-D/nicosulfuron** 1.9 + 90/20 T1/T2 94 96 92 101.4 Florasulam + 2.4-D/rimsulfuron** 1.9 + 90/7.5 T1/T2 99 98 92 92.2 Florasulam + 2.4-D/foramsulfuron + iodosulfuron** 1.9 + 90/15 + 0.5 T1/T2 92 96 95 92.3 Fluroxypyr/nicosulfuron** 250/40 T1/T2 100 100 99 106.1 Fluroxypyr/nicosulfuron** 125/20 T1/T2 86 85 92 92.4 Fluroxypyr/rimsulfuron** 125/7.5 T1/T2 95 93 85 98.1 Fluroxypyr/foramsulfuron + iodosulfuron** 125/15 + 0.5 T1/T2 85 94 91 104.7 LSD0.05 – NIR0,05 12.87

Combination – Kombinacja

Dose of a.s. Dawka s.a. g·ha-1

Table 3. Effectiveness of weed control in silage maize with protection technology based on two treatments with lower herbicide doses (Rawicz 2007) Tabela 3. Skuteczność zwalczania chwastów w kukurydzy uprawianej na kiszonkę po zastosowaniu technologii ochrony opartej na 2 zabiegach z obniżonymi dawkami herbicydów (Rawicz 2007 r.)

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Application time* Termin zabiegu

Weed control effectiveness Skuteczność zniszczenia chwastów % Plant height Wysokość roślin cm

Agricultura 10(2) 2011 20.0 20.9 22.2 21.2 15.8 16.1 15.3 15.6 4.47

12.2 20.1 16.4 17.4 19.1

10.2

100 maize cob mass Masa 100 kolb kukurydzy kg

* application time – termin zabiegu: T0 – in-soil, pre-emergence treatment – doglebowo, przed wschodami kukurydzy, T1 – on-leaf, post emergence, at the 1-3 maize leaf stage – nalistnie, w fazie 1-3 liści kukurydzy, T2 on-leaf, post emergence, at the 4-6 maize leaf stage – nalistnie, w fazie 4-6 liści kukurrydzy ** herbicide with the addition of adjuvant Atpolan Bio80 SL at the dose of 1.0 dm3·ha-1 – herbicyd z dodatkiem adiuwanta Atpolan Bio 80 SL w dawce 1.0 dm3·ha-1 CHEAL – Chenopodium album, SOLNI – Solanum nigrum, POLCO – Polygonum convolvulus

CHEAL SOLNI POLCO Two treatment system – in-soil (T0) and on-leaf (T1) – System dwóch zabiegów – doglebowy (T0) i nalistny (T2) Control, plant·m-2 / % in total weed population 106 / 67 / 7/ – – 158.5 Kontrola, szt.·m-2 / % w ogólnej populacji chwastów 57% 36% 0.5% Acetochlor 2100 T0 9 85 95 170.0 Acetochlor/nicosulfuron** 840/40 T0/T2 90 98 91 175.5 Acetochlor/nicosulfuron** 840/20 T0/T2 70 83 40 168.2 Acetochlor/rimsulfuron** 840/7.5 T0/T2 81 55 85 172.5 Acetochlor/foramsulfuron + iodosulfuron** 840/15 + 0.5 T0/T2 88 92 85 174.2 Two on-leaf treatment system T1 and T2 – System dwóch zabiegów nalistnych – T1 i T2 Florasulam + 2.4-D/nicosulfuron** 3.8 + 180/40 T1/T2 98 99 100 171.7 Florasulam + 2.4-D/nicosulfuron** 1.9 + 90/20 T1/T2 97 99 92 190.8 Florasulam + 2.4-D/rimsulfuron** 1.9 + 90/7.5 T1/T2 94 100 94 183.8 Florasulam + 2.4-D/foramsulfuron + iodosulfuron** 1.9 + 90/15 + 0.5 T1/T2 92 99 94 175.0 Fluroxypyr/nicosulfuron** 250/40 T1/T2 96 100 97 163.9 Fluroxypyr/nicosulfuron** 125/20 T1/T2 87 99 98 167.1 Fluroxypyr/rimsulfuron** 125/7.5 T1/T2 92 98 99 166.7 Fluroxypyr/foramsulfuron + iodosulfuron** 125/15 + 0.5 T1/T2 91 97 91 168.3 LSD0.05 – NIR0,05 12.45

Combination – Kombinacja

Dose of a.s. Dawka s.a. g·ha-1

Table 4. Effectiveness of weed control in grain maize with protection technology based on two treatments with lower herbicide doses (Winna Góra 2008) Tabela 4. Skuteczność zwalczania chwastów w kukurydzy uprawianej na ziarno po zastosowaniu technologii ochrony opartej na 2 zabiegach z obniżonymi dawkami herbicydów (Winna Góra 2008 r.)

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Application time* Termin zabiegu CHEAL

POLCO

CENCY

88 62 81 94 93 88 100 100

100 100 98 100 100 100 95 95

stage – nalistnie, w fazie 1-3 liści kukurydzy, T2 – on-leaf, post emergence, at the 4-6 maize leaf stage – nalistnie, w fazie 4-6 liści kukurrydzy ** herbicide with the addition of adjuvants Atpolan Bio80 SL at the dose of 1.0 dm3·ha-1 – herbicyd z dodatkiem adiuwanta Atpolan Bio 80 SL w dawce 1.0 dm3·ha-1 CHEAL – Chenopodium album, POLCO – Polygonum convolvulus, CENCY – Centaura cyanus, GALAP – Galium aparine, VIOAR – Viola arvensis

* application time – termin zabiegu: T0 – in-soil, pre-emergence treatment – doglebowo, przed wschodami kukurydzy, T1 – on-leaf, post emergence, at the 1-3 maize leaf

11 / 6% 0 100 75 40 25

VIOAR

22 / 12% 95 100 100 100 100

GALAP

Weed control effectiveness – Skuteczność zniszczenia chwastów %

Two treatment system – in-soil (T0) and on-leaf (T1) – System dwóch zabiegów – doglebowy (T0) i nalistny (T2) Control, plant.·m-2 / % in total weed population 53 / 64 / 28 / – – 29% 35% 15% Kontrola, szt.·m-2 / % w ogólnej populacji chwastów Acetochlor 2100 T0 55 15 55 Acetochlor/nicosulfuron + rimsulfuron** 840/17.2 + 4.3 T1/T2 92 23 50 Acetochlor/nicosulfuron** 840/20 T1/T2 85 50 30 Acetochlor/rimsulfuron** 840/7.5 T1/T2 85 52 59 Acetochlor/foramsulfuron + iodosulfuron** 840/15 + 0.5 T1/T2 98 30 63 Two on-leaf treatment system T1 and T2 – System dwóch zabiegów nalistnych – T1 i T2 Florasulam + 2.4-D/nicosulfuron + rimsulfuron** 3.8 + 180/17.2 + 4.3 T1/T2 99 84 99 Florasulam + 2.4-D/nicosulfuron** 1.9 + 90/20 T1/T2 97 80 98 Florasulam + 2.4-D/rimsulfuron** 1.9 + 90/7.5 T1/T2 87 91 96 Florasulam + 2.4-D/foramsulfuron + iodosulfuron** 1.9 + 90/15 + 0.5 T1/T2 100 90 100 Fluroxypyr /nicosulfuron + rimsulfuron ** 250/17.2 + 4.3 T1/T2 70 99 100 Fluroxypyr /nicosulfuron** 125/20 T1/T2 71 99 100 Fluroxypyr /rimsulfuron** 125/7.5 T1/T2 62 100 100 Fluroxypyr /foramsulfuron + iodosulfuron** 125/15 + 0.5 T1/T2 90 98 100 LSD0.05 – NIR0,05

Combination – Kombinacja

Dose of a.s. Dawka s.a. g·ha-1

Table 5. Effectiveness of weed control in grain maize with protection technology based on two treatments with lower herbicide doses (Nieczajna 2009) Tabela 5. Skuteczność zwalczania chwastów w kukurydzy uprawianej na ziarno po zastosowaniu technologii ochrony opartej na 2 zabiegach z obniżonymi dawkami herbicydów (Nieczajna 2009)

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Agricultura 10(2) 2011

61.8

41.2

14.3

117.3

13.3

18.5

13.6

rainfall opady mm

9.1

temperature temperatura o C

2006

15.7

19.3

17.5

10.4

temperature temperatura o C

88.0

45.4

13.0

rainfall opady mm

146.4

2007

13.6

18.1

14.4

8.4

temperature temperatura o C

2008

Table 6. Weather conditions in maize growth seasons Tabela 6. Warunki pogodowe w sezonach wegetacji kukurydzy

rainfall temperature opady temperatura o C mm April – Kwiecień 35.6 11.2 May – Maj 10.7 13.1 June – Czerwiec 8.4 15.3 Mean – Średnia 54.7 13.2 72.4

18.6

rainfall opady mm

191.3

100.3

2009

14.1

17.8

14.6

9.8

temperature temperatura o C

127.4

52.8

42.4

32.3

rainfall opady mm

Mean – Średnia 2006-2009

12.9

16.3

13.8

8.5

temperature temperatura o C

152.2

64.0

50.0

38.2

rainfall opady mm

Many-years mean Średnia wieloletnia

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Fig. 1. Rys. 1.

Rainfall and mean air temperature in 2006 (Winna Góra) Opady deszczu i średnia dobowa temperatura powietrza w 2006 roku (Winna Góra)

Fig. 2. Rys. 2.

Rainfall and mean air temperature in 2007 (Rawicz) Opady deszczu i średnia dobowa temperatura powietrza w 2007 roku (Rawicz)

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Fig. 3. Rys. 3.

Rainfall and mean air temperature in 2008 (Winna Góra) Opady i średnia dobowa temperatura powietrza w 2008 roku (Winna Góra)

Fig. 4. Rys. 4.

Rainfall and mean air temperature in 2009 (Gaj Mały – about 10 km away from Nieczajna) Opady i średnia dobowa temperatura powietrza w 2009 roku (Gaj Mały – około 10 km od Nieczajny)

Effect on the cultivated plant In the first year of the experiment, plant height and maize cob yield were not determined. In the following years, the smallest plants were on the control plots (1.3-1.7 m). Maize plant height in 2007 was levelled regardless of the weeding system. In the following year, maize with the contribution of in-soil treatments was significantly higher (1.88-2.55 m) than after two on-leaf treatments (1.44-2.02 m). The reason for this was probably the effective usage of April precipitation (35.6 mm), very close to the many-years average (38.2 mm). Mass of 100 cobs in both years usually depended on the effectiveness of the control of mass-occurring Ch. album. Higher mass of 100 cobs was obtained in the weeding system based on in-soil and on-leaf treatments than in the case

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of two on-leaf treatments. In 2007, after two times application of fluroxypyr, cob mass did not differ significantly from the mass of cobs collected from the control plot. In the remaining combinations, no statistical differences in the mass of 100 cobs were found. In both research years, the highest yields were obtained from the combinations in which the in-soil – on-leaf weed control system was applied (acetochlor/florasulam + 2.4-D, linuron/florasulam + 2.4-D, and linuron/dicamba). Lower mass of 100 cobs in both years was found after the application of acetochlor/dicamba. In 2007, mass of 100 cobs in this combination was significantly lower than the one obtained only on one plot, and in 2008 it was lower than cob mass from all the plots. After the application of two on-leaf treatments in 2007, no statistical differences were found (except the discussed combination of fluroxypyr/fluroxypyr) between the tested combinations. In 2008, mass of 100 maize cobs obtained after the application of the combination of active substances in combinations dicamba/fluroxypyr and fluroxypyr/fluroxypyr was significantly lower than the yields from the remaining combinations. After the application of combination florasulam + 2.4-D, the obtained cob masses were significantly higher than the control and did not differ between themselves. The applied active substances did not cause maize damage. Effect of weed control technology based on two treatments with lower doses – experiments carried out in years 2007-2009 Treatments in the first system were carried out in-soil and on-leaf at the 4-6 maize leaf stage. In the second system, the first treatment was carried out when maize developed 1-3 leaves, and the second one at the 4-6 leaf stage (Tables 3-5). Weed developmental stage did not determine treatment time but weeds never reached the stage beyond four true leaves. Herbicide effect In the three-year-long experiments, every year Ch. album occurred (Tables 3-5) – in the first year 20 plants·m2, which amounted to 12% of the entire weed population, whereas in the following years it was respectively: 106 plants (57%) and 53 plants (29%). Also, numerous emergences of Polygonum sp. were noted. Number of this plant species equalled 20 plants per 1 m2 (12% of the population). It was represented by the following species: P. convolvulus, P. nodosum, and P. aviculare. In the second and third year, only P. convolvulus was noted, respectively: 7 plants·m2 (0.5% of the population) and 64 plants·m2 (35% of the population). Other species occurred only in single experiments. In 2008, mass occurrence of Solanum nigrum was found (106 plants·m2 – 36% of the population), and in 2009 Centaurea cyanus (28 plants·m2 – 15%), Galium aparine (22 plants·m2 – 12%), and Viola arvensis (11 plants·m2 – 6%). The only representative of monocotyledonous weeds was in 2007 Echinochloa crus-galli, which occurred at the density of 120 plants·m2 and amounted to 67% of the entire weed population. Good and very good results were obtained in Ch. album control after in-soil and onleaf treatments. In 2007, herbicide effect oscillated between 99-100% regardless of the applied nicosulfuron dose. In the following two years, the effect of weed control was significantly lower (70-88%) and depended on the applied nicosulfuron dose. Applied

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in the same system acetochlor, and subsequently foramsulfuron + iodosulfuron, limited the occurrence of Ch. album in the three-year-long research in 88-98%. Alone acetochlor had a very poor effect (9% effectiveness) due to very low rainfall in 2008, three times lower than the many-years average. Mixtures in which instead of acetochlor applied in-soil, at the 1-3 maize leaf stage florasulam + 2.4-D or fluroxypyr were applied, destroyed Ch. album within the range of 85-100%. In 2009 (Table 5), lower effectiveness of its destruction was found only in those combinations in which fluroxypyr was used in the first treatment (62-90%). In the first year of the experiment, all the experimental combinations effectively limited (in 85-99%) the occurrence of species from genus Polygonum sp. (Table 3). In the following years, only the presence of P. convolvulus was noted. Its destruction amounted to 85-100%. In terms of herbicidal activity, the exception was the combination in which in-soil acetochlor and on-leaf nicosulfuron were used at a lower dose (40% destruction in 2008). In 2009, preparations applied in the in-soil – on-leaf system with mass-occurring P. convolvulus (35% of the total weed population) limited this species within the range of 23-52%. Higher herbicide effect in relation to this species, equal to 80-100%, was obtained after the application of only on-leaf treatments. Significantly better results were obtained by combinations with the use of florasulam + 2.4-D. Very similar effect was obtained with Centaurea cyanus control. The species occurred only in 2009. In the same year, a very good result was given by the application of both weeding systems in relation to Galium aparine (95-100% destruction). Viola arvensis that occurred in one experiment was destroyed in a diversified way. One hundred percent destruction was stated in the in-soil – on-leaf system after the application of acetochlor, and subsequently nicosulfuron with rimsulfuron and in the on-leaf system after the application of fluroxypyr with rimsulfuron and fluroxypyr with the mixture of foramsulfuron and iodosulfuron. Slightly lower effect (88-94%) was obtained after all the treatments except the combination of florasulam with nicosulfuron and the remaining in-soil – on-leaf treatments. Dicotyledonous species that occurred only once was Solanum nigrum. This species was very effectively destroyed by on-leaf (97-100%) and in-soil – on-leaf (83-98%) treatments, except the combination of acetochlor with rimsulfuron (55%). The only representative of monocotyledonous weeds which occurred in masses in 2007, covering plots in 67%, was species Echinochloa crus-galli. This weed was destroyed by in-soil and on-leaf treatments in 99-100%, and by two on-leaf treatments in 85-100%. Effect on the cultivated plant In 2007, 100 cob yield was determined (Table 3). In comparison with the control, it was significantly higher after the application of the combination of acetochlor (in-soil) with nicosulfuron (on-leaf) at the highest dose and the compounds applied in two onleaf treatments: florasulam + 2.4D/nicosulfuron in both doses. Cob mass from the remaining plots did not differ significantly. Determined in the same experiment green mass yield (whole plants – cobs with stems) obtained after the application of all treatment combinations was significantly higher from the control. The highest yields were noted after the application of the highest herbicide doses. They differed significantly from certain ones calculated from the remaining plots, although no connection with the doses was noted. In the following year (Table 4), differences in 100 cob yields were significantly higher. Maize plant height on the tested plots oscillated Agricultura 10(2) 2011

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between 163.9 and 190.8 m and in all the cases was greater than that of the control plants (158.5 m). In the last year of the experiment, analyses were not carried out. No maize damage was found caused by the application of different herbicide combinations. DISCUSSION At the Department of Weed Science and Plant Protection Techniques, for the last more than ten years, research has been carried out on the possibilities of improving herbicide effect through the application of lower doses, split doses, and adjuvant addition (support). In the experiments presented in the work, all three factors were taken into account. One of the most burdensome maize weeds is Ch. album. In the experiments by IPP – NRI Poznań, very good effects were obtained after lowering florasulam + 2.4-D dose by 50% for the first treatment and foramsulfuron with iodosulfuron for the second treatment. Gołębiowska and Kaus [2009a] after the application of an identical mixture in split doses found a satisfactory effect in relation to Ch. album and other species. This effectiveness was obtained using the combinations jointly with adjuvant Actirob 842 EC. In the present study, Atpolan Bio 80 EC was used as adjuvant. Favourable effect of adding this adjuvant was noted on the effectiveness of herbicides applied as second on-leaf treatments. In the studies by Gołębiowska and Kaus [2009a] and in the present study, similar results were obtained also in the destruction of S. nigrum and E. crus-galli. Poor effects of Ch. album control were found on most plots weeded with fluroxypyr. This is the compound to which Ch. album is fairly sensitive, which was confirmed in the research. High effectiveness in E. crus-galli control (85-100%) was obtained in the system of split doses, using mainly acetochlor and sulfonylurea preparations. For effective maize weeding with the use of a system based on in-soil and on-leaf herbicide application, significant soil humidity was necessary during the first in-soil treatment. In the present study, in years with favourable precipitation balance right before and after the in-soil treatment, optimal amount of water in the soil made active acetochlor action possible. Kneżević et al. already in 2003 published a work in which they presented the effects of the application in the same system of metolachlor, sulfonylurea herbicides, and in lower doses metolachlor with atrazine. The authors found the destruction of E. crus-galli and dicotyledonous weeds to have been at the level of 95-97%. Skrzypczak et al. [2007], using at different dose levels mezotrion + pethoxamid with terbuthylazine, obtained herbicide effectiveness within the range of 91-100% in relation to E. crus-galli, Ch. album, V. arvensis, P. aviculare, and P. convolvulus. In the present study, during which other active substances at lower doses were used, the results were comparable, with the exception of herbicide effect in relation to V. arvensis. Mass of 100 maize cobs obtained after the use of lower doses and after treatments in the system of split doses was higher than the control yields. This increase was proved statistically for many herbicide combinations. Not always the relation between herbicide doses and cob mass was found. This confirms good effectiveness of the studied systems, based on the application of lower herbicide doses. Kneżević et al. [2003], using herbicides at split and lower doses, showed a significant increase in cob yield. Similar results were also obtained by Skrzypczak et al. [2007] in relation to maize cobs and

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grain. After atrazine withdrawal, the applied alternative mixtures at lower doses also showed a significant effect on the increase in maize cob mass in relation to the control [Paradowski 2008]. Application of herbicides at lower doses and/or in the system of split doses requires perfect conditions, including proper growth and precise treatment. It ought to be accompanied also by optimal weather conditions. Rather high precipitation deviation from the many-years average during the experiment would certainly have a negative effect on proper maize development and would have a decreased herbicide effect. Optimal weather conditions have a direct effect on maize development (resistance to herbicides) and weed development (sensitivity to herbicides). This factor is paid special attention to by many authors who study the effectiveness of maize weeding depending on herbicide application method [James et al. 2000, 2006, Gąsiorowska and Makarewicz 2008, Gołębiowska and Snopczyński 2008]. When analyzing the results of the present study and of those by other authors, it ought to be stated that the research direction is right and economically justified. The obtained results at least in part could be put into practice to the benefit of maize planters. Unfortunately, procedure and registration proceedings are a hindrance. Registration motion for any kind of weed control system must be put forward by herbicide producers. However, producers are rarely interested in positive results concerning the application of lower doses. CONCLUSIONS 1. There is a possibility to control maize weeds effectively with the use of lower herbicide doses in the system of two treatments. 2. Satisfactory effectiveness of weed control against some dicotyledonous weeds and Echinochloa crus-galli was obtained after the in-soil application of lowered by 60% acetochlor dose and lowered by 50% nicosulfuron and rimsulfuron doses, as well as the mixtures of nicosulfuron + rimsulfuron and foramsulfuron + iodosulfuron applied on-leaf. 3. Effective herbicide result in relation to some weeds was obtained by lowering by 50% the mixture dose of florasulam + 2.4-D applied on-leaf in the first treatment and nicosulfuron, rimsulfuron, or foramsulfuron + iodosulfuron in the second treatment. Combinations of this system within the range of 90% to 100% controlled the following dicotyledonous weed species: C. cyanus, Ch. album, E. crus-galli, G. aparine, Polygonum sp., Solanum nigrum, and Viola arvensis. 4. Combinations in which fluroxypyr was used in the first treatment and nicosulfuron, rimsulfuron, or foramsulfuron + iodosulfuron in the second one, worked effectively for the occurring weeds with the exception of Chenopodium album. In all the experiments, it was shown that the combination applied at lower doses with the use of the mixture of florasulam + 2.4-D is the best component for weed control system based on two treatments. 5. Yields of 100 maize cobs and maize green mass after the application of lower herbicide doses were mostly significantly higher than the yields from the untreated plots (without treatments).

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REFERENCES Adamczewski K., Matysiak R., 2005. Znaczenie i korzyści wynikające ze stosowania adiuwantów z herbicydami sulfonylomocznikowymi [Significance and advantages that result from the application of adjuvants with sulfonylurea herbicides]. Prog. Plant Protection/ Post. Ochr. Roślin 45(1), 17-24 [in Polish]. Gąsiorowska B., Makarewicz A., 2008. Skuteczność działania wybranych herbicydów w uprawie kukurydzy [Effectiveness of chosen herbicides in maize growth]. Prog. Plant Protection/Post. Ochr. Roślin 48(2), 578-581 [in Polish]. Gołębiowska H., 2006. Wpływ sposobu aplikacji herbicydów na poziom zachwaszczenia wtórnego w kukurydzy [Effect of herbicide application method on secondary infestation level in maize]. Prog. Plant Protection/ Post. Ochr. Roślin 46(2), 265-268 [in Polish]. Gołębiowska H., Kaus A., 2009a. Efektywność chemicznej regulacji zachwaszczenia w różnych systemach uprawy kukurydzy [Effectiveness of chemical infestation regulation in different maize growth systems]. Acta Sci. Pol., Agricultura 8(1), 3-16 [in Polish]. Gołębiowska H., Kaus A., 2009b. Wpływ zróżnicowanych systemów uprawy na stan zachwaszczenia kukurydzy [Effect of diversified growth systems on maize infestation]. Prog. Plant Protection/Post. Ochr. Roślin 49(2), 792-796 [in Polish]. Gołębiowska H., Snopczyński T., 2008. Wzrost zagrożenia zachwaszczeniem wtórnym na plantacji kukurydzy na tle zróżnicowanego przebiegu pogody [Increase in secondary infestation threat in maize plantation against diversified weather course]. Prog. Plant Protection/ Post. Ochr. Roślin 48(2), 602-611 [in Polish]. James T.K., Rahman A., Mellsop J., 2000. Weed competition in maize crop under different timings for post-emergence weed control. New Zeland Plant Protection 53, 269-272 James T.K., Rahman A., Trolove M., 2006. Optimal timing for post emergence applications of nicosulfuron for weed control in maize. New Zeland Plant Protection 59, 250-254. Kierzek R., Adamczewski K., 2008. Możliwości łącznego stosowania mieszanin herbicydów w kukurydzy [Possibilities of joint application of herbicide mixtures in maize]. Prog. Plant Protection/Post. Ochr. Roślin 48(3), 1146-1149 [in Polish]. Kierzek R., Miklaszewska K., 2009. Redukcja zachwaszczenia kukurydzy poprzez stosowanie herbicydów z adiuwantami oraz różnymi technologiami uprawy [Maize infestation reduction through the application of herbicides with adjuvants and various growth technologies]. Prog. Plant Protection/Post. Ochr. Roślin 49(2), 811-818 [in Polish]. Kneżević M., Durkić M., Kneżević I., Lonćarić Z., 2003. Effects of pre- and post-emergence weed control on weed population and maize yield in different tillage systems. Plant Soil Environ. 49(5), 223-229. Matysiak R., Woźnica Z., Pudełko J., Skrzypczak G., 1995. Adiuwant do herbicydów – mechanizm działania [Herbicide adjuvants – action mechanism]. Materiały 35. Sesji Nauk. Inst. Ochr. Roślin 2, 67-86 [in Polish]. Paradowski A., 2008. Alternatywa dla atrazyny w kukurydzy [Alternative for atrazine in maize]. Prog. Plant Protection/Post. Ochr. Roślin 48(2), 640-645 [in Polish]. Paradowski A., Kierzek R., 2009. Ekonomiczne aspekty chemicznego odchwaszczania kukurydzy po wycofaniu atrazyny [Economic aspects of chemical maize weeding after atrazine withdrawal]. Prog. Plant Prot./Postęp Ochr. Roślin. 49(4), 1630-1636 [in Polish]. Praczyk T. Adamczewski K., 1996. Znaczenie adiuwantów w chemicznej ochronie roślin [Significance of adjuvants in chemical plant protection]. Prog. Plant Protection/Post. Ochr. Roślin 36(1), 117-121 [in Polish]. Rola J., Rola H., 1995. Wpływ uproszczonej technologii uprawy kukurydzy i buraków cukrowych na stan zachwaszczenia wtórnego plantacji na Dolnym Śląsku [Effect of the simplified growth technology of maize and sugar beets on the secondary infestation of a plantation in Lower Silesia]. Materiały 35. Sesji Nauk. Inst. Ochr. Roślin, cz. 1, 139-145 [in Polish].

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Skrzypczak G., Pudełko J., Blecharczyk A., 1998. Ocena działania herbicydów i adiuwantów w uprawie kukurydzy [Assessment of herbicide and adjuvant effectiveness in maize growth]. Prog. Plant Protection/ Post. Ochr. Roślin 38(2), 698-700 [in Polish]. Skrzypczak G., Pudełko J., Waniorek W., 2007. Assessment of the tank mixture of mesotrione and penhoxamid plus terbuthylazine efficacy for weed control in maize (Zea mays L.). J. Plant Protection Res. 47, 375-381. Snopczyński T., Gołębiowska H., 2008. Ocena skuteczności chwastobójczej mieszaniny mezotrion + terbutyloazyna + S-metolachlor w uprawie kukurydzy [Assessment of the herbicide effectiveness of the mixture of mezotrion + terbuthylazine + S-metolachlor in maize growth]. Prog. Plant Protection/Post. Ochr. Roślin 48(2), 674-677 [in Polish]. Woźnica Z., Miłkowski P., Waniorek W., 1997. Adiuwanty a skuteczność chwastobójcza herbicydów [Adjuvants versus herbicide effectiveness]. Prog. Plant Protection/ Post. Ochr. Roślin 37(2), 190-192 [in Polish]. Woźnica Z., Skrzypczak G., 1998. Adjuvants for foliar applied herbicides. Ann. Warsaw Agric. Univ., Agriculture 32, 33-42.

EFEKTYWNOŚĆ ODCHWASZCZANIA KUKURYDZY (Zea mays L.) W ZALEŻNOŚCI OD TERMINU I METODY APLIKACJI HERBICYDÓW Streszczenie. W latach 2006-2009 przeprowadzono 6 ścisłych doświadczeń polowych, których celem była ocena działania herbicydów używanych do odchwaszczania kukurydzy w obniżonych dawkach i różnych terminach. Herbicydy stosowano w trzech wariantach: (1) dwukrotnie na chwasty w fazie nie przekraczającej 2 liści właściwych, bez względu na fazę rozwojową kukurydzy, (2) zabieg doglebowy + zabieg nalistny, (3) dwa zabiegi nalistne – w fazie 1-3 oraz 4-6 liści kukurydzy. W badaniach wykorzystano następujące substancje aktywne: acetochlor, dikamba, linuron, florasulam + 2,4-D, fluroksypyr, foramsulfuron + jodosulfuron, nikosulfuron, nikosulfuron + rimsulfuron i rimsulfuron. Badania wykazały, że po zastosowaniu obniżonych dawek herbicydów istnieje możliwość uzyskania zadowalającego efektu chwastobójczego. Ograniczenie liczby chwastów i zahamowanie ich rozwoju pozwoliło uzyskać plony nie różniące się istotnie od uzyskanych po zabiegach w dawkach standardowych. Najlepszym komponentem w badanych mieszaninach herbicydów okazała się kombinacja florasulam + 2,4-D. W przypadku dużego nasilenia Chenopodium album L. jako komponentu mieszaniny nie należy stosować fluroksypyru. Stwierdzono, że w warunkach opóźniających się i nierównomiernych wschodów chwastów system dwóch zabiegów z obniżonymi dawkami herbicydów skutecznie ograniczał zachwaszczenie kukurydzy w dłuższym okresie wegetacji. Słowa kluczowe: dawki dzielone, mieszanina herbicydowa, obniżona dawka herbicydu, zachwaszczenie kukurydzy, zwalczanie chwastów

Accepted for print – Zaakceptowano do druku: 11.04.2011

Agricultura 10(2) 2011