INFLUENCE OF HERBICIDE APPLICATION TIMINGS, RATES AND ADJUVANT TYPE ON WEED CONTROL AND YIELD OF MAIZE GROWN FOR FORAGE

, Agricultura 9(4) 2010, 77-84 INFLUENCE OF HERBICIDE APPLICATION TIMINGS, RATES AND ADJUVANT TYPE ON WEED CONTROL AND YIELD OF MAIZE GROWN FOR FORAGE Zenon Woźnica, Robert Idziak Poznań University of Life Sciences 1 Abstract. Field experiments were carried out in 2008 and 2009 to develop an efficacious and cost-effective weed control program for maize. Herbicides containing terbuthylazine (Click 500 SC), nicosulfuron (Accent 75 WG) and tritosulfuron + dicamba (Mocarz 75 WG) were applied in tank-mixtures at reduced rates, sequentially at 14- to 18-day intervals with nonionic surfactant Trend 90 EC or methyleted seed oil adjuvant Atpolan Bio 80 EC. These standard herbicides were also applied once at recommended timing and rates, without adjuvant. Maize was infested mostly with Chenopodium album L., Polygonum convolvulus (L.) Á. Löve and Echinochloa crus-galli (L.) P. Beauv. Broadleaf plus grass weed control with standard herbicide treatment of Click 500 SC, Accent 75 WG and Mocarz 75 WG was only 28, 6 and 21%, respectively. Herbicide tank-mixtures applied sequentially at reduced rates with adjuvants greatly increased weed control and weed control consistency that ranged between 92 and 99%. Atpolan Bio 80 EC was more effective adjuvant then Trend 90 EC. Sequential application of herbicide mixtures with adjuvants provided high increase of maize grain yield (as compared with the control by 9.36-10.38 t ha -1 ) and high net return (from 4037 to 4482 PLN ha -1 ). Benefits from standard herbicide treatments applied once at recommended rates without adjuvant were significantly lower (grain yield increase by 0.49-2.60 t ha -1 and net return from -6 to1080 PLN ha -1 ). Key words: herbicide mixtures, non-ionic surfactant, oil adjuvant, split application of herbicides, weed infestation of maize INTRODUCTION Maize (Zea mays L.), due to its very slow growth and low density, is easily infested by weeds, which usually leads to a heavy reduction, and even the complete loss of yield [Zimdahl 1980, Rola 1986, Kells 1999, Idziak and Woźnica 2008]. For this reason, effective weed control, currently based almost exclusively on herbicide application, is Corresponding author Adres do korespondencji: prof. dr hab. Zenon Woźnica, Department of Agronomy of Poznań University of Life Sciences, Mazowiecka 45/46, 60-623 Poznań, e-mail: woznica@up.poznan.pl

78 Z. Woźnica, R. Idziak absolutely necessary. Leaving even a small number of weeds characterizing with a great competitiveness, especially common lambsquarters (Chenopodium album L.), green amaranth (Amaranthus retroflexus L.) and barnyard grass (Echinochloa crus-galli (L.) P. Beauv.) is, besides the unfavorable course of the weather conditions, one of the most common factors that reduces the potentially high yield-forming capacity of maize and the maximum economic benefits in the given conditions. The studies and observations of agricultural practice to date indicate that in spite of withdrawing of use herbicides based on atrazine and simazine, effective weed control in maize with herbicides from other chemical groups is fully possible, yet more expensive and burdened with a higher risk of the occurrence of secondary weed infestation. The usually changeable state of maize weed infestation and a gradual increase in weed species with higher thermal requirements appearing imply a more precise selection of herbicides and the use of mixtures of several active substances supplementing one another in one application [Kudsk 2002]. Many studies stress also significance of selecting appropriate activator adjuvants to the spray liquid in order to reduce the effect of factors hindering retention of spraying droplets on the surface of weeds and absorption and transport of herbicide active substances to the place of action [Nalewaja et al. 1986, Praczyk and Adamczewski 1996, Woźnica and Skrzypczak 1998]. Also it seems that in modern weed control programs in maize, generally without of residual, soil-applied herbicides (except for terbuthylazine), a higher efficiency of weed control, as well as a more reliable herbicide action in different conditions of weed infestation and the course of weather, can be obtained by means of using a mixture of active substances in two sequential applications conducted at several-day or even twenty-day intervals [Idziak and Woźnica 2009]. A merit of such herbicide application, especially if active substances with various mode of action are present in the mixture, is also inhibiting the selection of weed biotypes resistant to herbicides and for this reason it should be especially preferred [Woźnica et al. 1996, Rola and Rola 2002]. However, sequential herbicide application is burdened with additional costs and organizational inconveniences. The aim of this study was to estimate if a sequential, split application of herbicide mixtures at reduced rates with activator adjuvants can contribute to ensure high herbicidal efficacy, an increase in maize yield and improvement of economic benefits of maize cultivation. MATERIAL AND METHODS A field experiment was carried out in 2008-2009 at the Experimental Research and Education Centre Gorzyń near Poznań (52 26 N; 16 18 E) on the sandy loam soil classified as the quality class IIIa. Plots with an area of 25 m 2 (2.5 x 10 m) were sown with maize hybrids PR 39B56 in a density of 8 pcs m -1 and 70-cm row spacing. Mineral fertilization of maize was applied in the amount of 140 kg N, 60 kg P and 60 kg K ha -1. The weed control treatments being the subject of this study were mixtures of the herbicides Click 500 SC (terbuthylazine) + Accent 75 WG (nicosulfuron) and Click 500 SC + Accent 75 WG + Mocarz 75 WG (tritosulfuron + dicamba) applied twice postemergence, at 14-18-day intervals (BBCH 12 and 15) and at rates reduced 2-4-times in relation to the recommended rates. These mixtures were applied with the non-ionic surfactant Trend 90 EC at a concentration of 0.1% or an adjuvant of oil origin the

Influence of herbicide 79 methyled ester of fatty acids with a build-in ph buffer (Atpolan Bio 80 EC) at a rate of 1.5 dm 3 ha -1. On the reference plots herbicides that were included in the mixtures were applied once at recommended rates and dates: Click 500 SC at 1.5 dm 3 ha -1, 3 days after maize sowing (BBCH 01), Accent 75 WG at 80 g ha -1, at the stage of 5 maize leaves (BBCH 15) and Mocarz 75 WG at 200 g ha -1, at the stage of 5 maize leaves (BBCH 15). Herbicides were applied with a plot sprayer equipped with flat fan nozzles Lurmark 02 110, and a spray volume was 200 dm 3 ha -1. Efficacy of the applied herbicides was estimated on the basis of the weight analysis of weeds carried out after 4 weeks from the last foliar application. Effect of the tested herbicide-adjuvant combinations on maize grain yield and net return from weed control was also determined. Net return from weed control was calculated from the difference between the value of grain yield gains of maize weeded by means of the given herbicide combinations, and the value of the applied herbicides, including the costs of their application. Average prices of maize grain, herbicides and adjuvants, and also the costs of pesticide application in Great Poland in 2009 were adopted for the calculations. The experiments were conducted in a randomized complete block design with four replications. Significance of differences among means were determined using analysis of variance and t-student test at P = 0.05 significance level (statistical calculations were made using the statistical program packet MSTAT-C, version 1.3). RESULTS In both years of the study climatic conditions at the initial period of maize vegetation were not very favorable for its growth and efficacy of the tested herbicides. In 2008 and 2009, total precipitation in 30-day period, involving the time from maize sowing to the 5-leaf stage (the third decade of April to the end of the second decade of May), when the herbicide applications were completed, were only 19.5 and 30.6 mm, respectively (Table 1). Low precipitation at that time was accompanied by relatively high air temperatures (Table 2). Dominant weed species occurring in maize were: common lambsquarters (Chenopodium album L.), black knotgrass (Polygonum convolvulus (L.) Á. Löve) and barnyard grass (Echinochloa crus-galli (L.) P. Beauv.). The efficacy of the soil applied herbicide Click 500 SC and the leaf-applied herbicides Accent 75 WG and Mocarz 75 WG sprayed once at recommended rates, was very low and amounted to 28.6 and 21%, respectively, in relation to the total weed infestation (Table 3). The herbicide Accent 75 WG, although it well controlled barnyard grass, led to the compensation of dicotyledonous species, mostly common lambsquarters. A relatively poor efficacy of the herbicide Click 500 SC resulted mainly from water deficit in soil, caused by low precipitation during the several-week period after its application. Meanwhile, on the treatment sprayed with the herbicide Mocarz 75 WG, which poorly controlled common lambsquarters and barnyard grass, also secondary weed infestation occurred, represented mainly by black knotgrass. Agricultura 9(4) 2010

80 Z. Woźnica, R. Idziak Table 1. Precipitations during maize growing period, mm Tabela 1. Opady w czasie wegetacji kukurydzy, mm Month Miesiąc April Kwiecień May Maj June Czerwiec July Lipiec August Sierpień September Wrzesień Mean total 1961-2008 Średnia suma z wielolecia 1961-2008 monthly total suma miesięczna 2008 2009 10-day period dekada monthly total 10-day period dekada I II III suma miesięczna I II III 38.5 120.7 49.2 71.5 0.0 13.3 1.1 4.5 7.7 56.1 19.5 1.4 18.1 0.0 85.3 7.8 15.1 62.4 62.3 8.6 0.0 4.2 4.4 79.3 30.0 29.9 19.4 77.3 80.1 7.0 73.1 0.0 68.1 25.4 28.2 14.5 67.7 171.5 15.1 136.8 19.6 31.4 13.5 17.9 0.0 48.8 29.8 13.5 1.5 14.8 50.0 22.1 6.1 21.8 Table 2. Air temperature during maize growing period, C Tabela 2. Temperatura powietrza w czasie wegetacji kukurydzy, C Month Miesiąc April Kwiecień May Maj June Czerwiec July Lipiec August Sierpień September Wrzesień Mean Średnia wieloletnia 1961-2008 monthly mean średnia miesięczna 2008 2009 10-day period dekada monthly mean 10-day period dekada I II III średnia miesięczna I II III 7.8 8.7 6.5 7.5 12.0 11.7 11.3 10.4 13.3 13.2 15.2 14.0 15.1 16.4 13.4 12.7 12.6 14.8 16.4 19.1 21.0 16.7 19.7 15.7 13.3 15.2 18.6 18.1 20.0 21.0 18.3 21.7 19.7 20.5 19.3 19.4 17.5 18.8 20.3 18.9 17.2 19.7 20.3 19.5 19.3 13.2 13.9 18.2 11.5 11.9 15.6 17.2 15.7 13.9 Mixtures of herbicides applied two times Click 500 SC + Accent 75 WG (0.75 dm 3 + 20 g ha -1 in each application) and Click 500 SC + Accent 75 WG + Mocarz 75 WG (0.75 dm 3 + 20 g + 50 g ha -1 in each application) with the surfactant Trend 90 EC (0.1%) or the oil adjuvant Atpolan Bio 80 EC (1.5 dm 3 ha -1 ) were very efficacious, reducing the weight of occurring weeds by 92-98%. Atpolan Bio 80 EC turned out to be a more effective adjuvant than Trend 90 EC, especially in mixture with the twocomponent and cheaper combination of herbicides Click 500 SC + Accent 75 WG. In this case, the herbicidal efficacy observed amounted to 99% and was similar to that obtained after the application of a more expensive mixture of three herbicides (Click 500 SC + Accent 75 WG + Mocarz 75 WG).

Influence of herbicide... 81 Table 3. Efficacy of herbicides, grain yield and profitability of weed control in maize Tabela 3. Wpływ herbicydów na skuteczność chwastobójczą, plony ziarna i opłacalność odchwaszczania kukurydzy Treatment Kombinacja Rate per 1 ha Dawka na 1 ha Time of application Termin stosowania Efficacy of herbicides Skuteczność chwastobójcza herbicydów % Grain yield Plon ziarna t ha -1 Value of grain yield enhancement, PLN ha -1 Wartość zwyżki plonu ziarna, zł ha -1 Cost of weed control, PLN ha -1 Koszt zwalczania chwastów, zł ha -1 Control Kontrola 0* b 2.00 b Click 500 SC 1.5 dm 3 BBCH 01 28 b 4.20 b 990 106 884 Accent 75 WG 80 g BBCH 15 6 b 2.49 b 220 226 6 Mocarz 75 WG 200 g BBCH 15 21 b 4.60 b 1170 90 1080 Click 500 SC + Accent 75 WG + Trend 90 EC Click 500 SC + Accent 75 WG + Atpolan Bio 80 EC Click 500 SC + Accent 75 WG + Mocarz 75 WG + Trend 90 EC Click 500 SC + Accent 75 WG + Mocarz 75 WG + Atpolan Bio 80 EC 0.75 dm 3 + 20 g + 0.1% BBCH 12 + BBCH 15 0.75 dm 3 + 20 g BBCH 12 + 1.5 dm 3 + BBCH 15 0.75 dm 3 + 20 g BBCH 12 + 50 g + 0.1% + BBCH 15 0.75 dm 3 + 20 g BBCH 12 + 50 g + 1.5 dm 3 + BBCH 15 Net return PLN ha -1 ** Opłacalność zwalczania chwastów zł ha -1 92 a 11.80 a 4410 160 4250 98 a 11.36 a 4212 175 4037 99 a 11.41 a 4234 173 4061 99 a 12.38 a 4671 189 4482 * fresh mass of weeds on untreated control plots was 2291 g m -2 świeża masa chwastów na poletkach kontrolnych wynosiła 2291 g m -2 ** calculations were made based on average prices of maize grain, herbicides, adjuvants and costs of application in October 2009 wyliczono na podstawie przeciętnych cen ziarna kukurydzy, herbicydów, adiuwantów i kosztów aplikacji z października 2009 r. Agricultura 9(4) 2010.

82 Z. Woźnica, R. Idziak Split application of herbicide mixtures with adjuvants allowed not only the elimination of weeds more tolerant towards individual components of the mixture, but also prevented the occurrence of secondary weed infestation. In spite of high herbicidal efficacy, none of the tested herbicide mixtures applied with adjuvants caused significant maize injuries. Some small and short-lived plant injuries were observed only in the treatments where the adjuvant Atpolan Bio 89 EC was included. Thanks to almost complete elimination of weeds, two-time application of a mixture of herbicides with an addition of adjuvants had an effect on maize grain yield increase by 9.36-10.80 t ha -1 ) as compared with the control treatment. In contrast, an increase in grain yield after the application of single herbicides once in recommended rates was only 0.49-2.60 t ha -1. The cost of tested mixtures of herbicides with adjuvants, together with the cost of their application, ranged from 160-189 PLN ha -1, as compared with 90-226 PLN ha -1 in the case of a single application of comparative herbicides. Taking into consideration a high herbicidal efficacy and consequently, a considerable growth in the value of grain yield harvested, the profitability of using herbicide mixtures with an addition of adjuvants amounted to 4037-4482 PLN ha -1 and was 3-4-times higher than that at using comparative herbicides at one time. DISCUSSION Currently available foliar-applied herbicides for maize weed control are characterized by a relatively short time of action, and the considerable majority of them are recommended for a single application during maize growing period. A single application of herbicides is certainly justified organizationally and economically, but it cannot be always carried out during the highest sensitivity of weeds to herbicides and it does not prevent the risk of secondary weed infestation. The conducted study confirmed that maize is exceptionally sensitive to weed infestation, since it responded on it with the almost complete loss of grain yield. A single application of standard herbicides Click 500 SC, Accent 75 WG and Mocarz 75 WG at rates and times recommended for agricultural practice proved to be complete ineffective. Lack of the efficiency of the tested herbicides may have resulted from their improper choice for the occurring weed species and exceptionally unfavorable weather conditions, especially very low precipitation during and after their application. Under such conditions, mixtures of those herbicides applied even in lowered rates but with adjuvants turned up to be very efficient. A selection of at least two active substances applied two times on weeds, in the period of their highest sensitivity, undoubtedly widened the spectrum of the eliminated weed species and increased their biological activity. Based on the previous analyses, it is possible to state with large probability that an addition of adjuvants to the spray liquid, especially methylated ester with ph buffer (Atpolan Bio 80 EC) contributed to an increased retention of spraying droplets on the surface of sprayed weeds and to a higher absorption of the active substance to plant cells [Nalewaja et al. 1986, Praczyk and Adamczewski 1996, Woźnica and Skrzypczak 1998]. Thus under conditions of water stress, which occurred in both years of the study, an addition of adjuvants could prove to be particularly favorable. The application of herbicides in mixture and at two dates, on weeds in the period of their highest sensitivity can be in such a situation a good solution and bring notable economic benefits, just as it was found in the case of elimination of persistent weeds on plantations of sugar beets

Influence of herbicide 83 [Dexter and Luecke 1998, Woźnica et al. 2007], cereals [Ramsdale and Messersmith 2002], legumes [Jensen 2006] and maize with another set of herbicides and adjuvants [Idziak and Woźnica 2009]. CONCLUSION Foliar, split-application of herbicide mixtures: Click 500 SC + Accent 75 WG (0.75 dm 3 + 20 g ha -1 in each application) and Click 500 SC + Accent 75 WG + Mocarz 75 WG (0.75 dm 3 + 20 g + 50 g ha -1 in each application) with the surfactant Trend 90 EC (0.1%) or the oil adjuvant Atpolan Bio 80 EC (1.5 dm 3 ha -1 ) at reduced rates ensured effective weed control in maize, as opposed to the use of the tested herbicides according to the recommendations at full rates, once and without an adjuvant. Atpolan Bio 80 EC proved to be a more effective adjuvant than Trend 90 EC. Applying a mixture of herbicides sequentially with adjuvants contributed to a high increase in grain yield (by 9.36-10.38 t ha -1 as compared with the control) and a high net return (4037-4482 PLN ha -1 ). REFERENCE Dexter A.G., Luecke J.L., 1998. Special survey on micro-rate, 1988. Sugarbeet Res. Ext. Rep. 29, 64-70. Idziak R., Woźnica Z., 2008. Skuteczność chwastobójcza herbicydu Callisto 100 SC stosowanego z adiuwantami i nawozem mineralnym [Efficacy of the herbicide Callisto 100 SC applied with adjuvants and a mineral fertilizer]. Acta Agrophys. 11(2), 403-410 [in Polish]. Idziak R., Woźnica Z., 2009. Ocena skuteczności chwastobójczej mieszaniny herbicydów Callisto 100 SC i Maister 310 WG stosowanych z adiuwantem olejowym i mineralnym stosowanych w uprawie kukurydzy [Assessment of efficacy of mixture of herbicides Callisto 100 SC and Maister 310 WG applied with oil and mineral adjuvants in maize cultivation]., Agricultura 8(1), 17-26 [in Polish]. Jensen P.K., 2006. Split application of herbicides in peas. Weed Res. 32(4), 295-302. Kells J.J., 1999. Weed competition in corn. Illinois Crop Protection Conference Proceedings, 63-64. Kudsk P., 2002. Optimising herbicide performance. [In:] Weed management handbook, R.E.L. Naylor (ed.), Blackwell Publishing, 323-344. Nalewaja J.D., Skrzypczak G.A., Gillespie G.R., 1986. Absorption and translocation of herbicides with lipid compounds. Weed Sci. 34, 564-568. Praczyk T., Adamczewski K., 1996. Znaczenie adiuwantów w chemicznej ochronie roślin [Role of adjuvants in chemical plant protection]. Prog. Plant Protection/Post. Ochr. Roślin 36(1), 117-121 [in Polish]. Ramsdale B.K., Messersmith C.G., 2002. Low-rate split-applied herbicide treatments for wild oat (Avena fatua) control in wheat (Triticum aestivum). Weed Technol. 16(1), 149-155. Rola H., 1986. Zależność wysokości plonów kukurydzy od okresu występowania w łanie Echinochloa crus-galli i Amaranthus retroflexus [Dependence of maize yield height on the period of occurrence of Echinochloa crus-galli and Amaranthus retroflexus in the stand]. Pam. Puł. 87, 15-170 [in Polish]. Rola H., Rola J., 2002. Teoria i praktyka uodparniania się chwastów segetalnych na herbicydy stosowane w Polsce [Theory and practice of segetal weed resistance to herbicides used in Poland]. Prog. Plant Protection/Post. Ochr. Roślin 41(1), 375-382 [in Polish]. Agricultura 9(4) 2010

84 Z. Woźnica, R. Idziak Woźnica Z., Adamczewski K., Manthey F.A., 1996. Biotypy chwastów odpornych na herbicydy [Biotypes of weeds resistant to herbicides]. Prog. Plant Protection/Post. Ochr. Roślin 36(1), 97-101 [in Polish]. Woźnica Z., Idziak R., Waniorek W., 2007. Mikrodawki herbicydów nowa opcja odchwaszczania buraków cukrowych [Microrates of herbicides a new option of weed control in sugar beet]. Prog. Plant Protection/Post. Ochr. Roślin 47(2), 310-315 [in Polish]. Woźnica Z., Skrzypczak G., 1998. Adjuvants for foliar applied herbicides. Ann. Warsaw Agricult. Univ. SGGW, Agriculture 32, 33-42. Zimdahl L.R., 1980. Weed-crop competition. A review. Inter. Plant Prot. Center. Oregon, State University Corvallis Inter. P. Prot. Center. WPŁYW TERMINÓW STOSOWANIA I DAWEK HERBICYDÓW ORAZ RODZAJU ADIUWANTA NA ZACHWASZCZENIE I PLONOWANIE KUKURYDZY PASTEWNEJ Streszczenie. Celem badań polowych wykonanych w latach 2008-2009 było opracowanie efektywnego pod względem biologicznym i ekonomicznym systemu odchwaszczania kukurydzy. Kombinacje, będące przedmiotem badań, stanowiły mieszaniny herbicydów zawierające terbutyloazynę (Click 500 SC), nikosulfuron (Accent 75 WG) oraz tritosulfuron + dikambę (Mocarz 75 WG). Mieszaniny te stosowano dwukrotnie, w odstępach 14-18-dniowych, w dawkach silnie zredukowanych, z dodatkiem adiuwantów surfaktanta niejonowego Trend 90 EC lub estru metylowego kwasów tłuszczowych Atpolan Bio 80 EC. Na obiektach porównawczych herbicydy wchodzące w skład mieszanin zastosowano jednorazowo, w zalecanej przez producenta dawce i terminie, bez adiuwanta. Dominującymi gatunkami chwastów w kukurydzy były: Chenopodium album L., Polygonum convolvulus (L.) Á. Löve oraz Echinochloa crus-galli (L.) P. Beauv. Skuteczność chwastobójcza herbicydów Click 500 SC, Accent 75 WG oraz Mocarz 75 WG stosowanych jednorazowo w zalecanych dawkach, bez adiuwanta w stosunku do ogółu chwastów była bardzo słaba i wynosiła odpowiednio 28,6 i 21%. Zastosowanie mieszanin tych herbicydów dwukrotnie, w dawkach zredukowanych z adiuwantami, było w pełni skuteczne (zniszczenie chwastów od 92-99%). Atpolan Bio 80 EC okazał się bardziej efektywnym adiuwantem niż Trend 90 EC. Stosowanie mieszaniny herbicydów w dawkach dzielonych z adiuwantami przyczyniło się do silnego wzrostu plonów ziarna (w porównaniu z kontrolą o 9,36-10,38 t ha -1 ) i uzyskania wysokiej opłacalności odchwaszczania kukurydzy (4037-4482 zł ha -1 ). Korzyści wynikające z odchwaszczania kukurydzy pojedynczymi herbicydami, stosowanymi jednorazowo w zalecanych dawkach i terminach bez dodatku adiuwanta, były zdecydowanie mniejsze (wzrost plonów o 0,49- -2,60 t ha -1, a opłacalność odchwaszczania od -6 do 1080 zł ha -1 ). Słowa kluczowe: adiuwant olejowy, dzielone dawki herbicydów, mieszaniny herbicydów, surfaktant niejonowy, zachwaszczenie kukurydzy Accepted for print Zaakceptowano do druku: 29.11.2010