Cover crops and herbicide timing management on soybean yield under no-tillage system

Abstract

-The objective of this work was to evaluate the effect of cover crops and timing of pre-emergence herbicide applications on soybean yield under no-tillage system. The experiment consisted of four cover crops (Panicum maximum, Urochloa ruziziensis, U. brizantha, and pearl millet) and fallow, in addition to four herbicide timings (30, 20, 10, and 0 days before soybean sowing), under no-tillage system (NTS), and of two control treatments under conventional tillage system (CTS). The experimental design was a completely randomized block, in a split-plot arrangement, with three replicates. Soybean under fallow, P. maximum, U. ruziziensis, U. brizantha, and pearl millet in the NTS and soybean under U. brizantha in the CTS did not differ significantly regarding yield. Soybean under fallow in the CTS significantly reduced yield when compared to the other treatments. The amount of straw on soil surface did not significantly affect soybean yield. Chemical management of P. maximum and U. brizantha near the soybean sowing date causes significant damage in soybean yield. However, herbicide timing in fallow, U. ruziziensis, and pearl millet does not affect soybean yield.Index terms: Glycine max, Panicum maximum, brachiaria, chemical management, herbicide timing, pearl millet. Plantas de cobertura e manejo da época de aplicação de herbicida na produção de soja em sistema plantio diretoResumo -O objetivo deste trabalho foi avaliar o efeito de plantas de cobertura e época de aplicação de herbicidas antes do semeio na produtividade da soja em plantio direto. O experimento consistiu em quatro plantas de cobertura (Panicum maximum, Urochloa ruziziensis, U. brizantha e milheto) e pousio, além de quatro épocas de aplicação de herbicidas (30, 20, 10 e 0 dias antes do semeio da soja), em sistema plantio direto (SPD), e em dois tratamentos controle em sistema convencional (SC). Utilizou-se o delineamento experimental de blocos ao acaso, com parcelas subdivididas e três repetições. Soja sobre pousio, P. maximum, U. ruziziensis, U. brizantha e milheto em SPD e soja sobre U. brizantha em SC não diferiram significativamente entre si quanto à produtividade. Soja sobre pousio em SC resultou em redução significativa na produtividade da soja, em comparação aos demais tratamentos. A quantidade de palha na superfície do solo não teve efeito significativo na produtividade da soja. O manejo químico de P. maximum e U. brizantha próximo à época de semeadura da soja causa dano significativo na produtividade da soja. Entretanto, a época de aplicação do herbicida após pousio, U. ruziziensis e milheto não afeta a produtividade da soja.Termos para indexação: Glycine max, Panicum maximum, braquiaria, manejo químico, época aplicação de herbicida, milheto.

Corn and soybean yields as affected by cover crops and herbicide timing under no-tillage system

“…Also Nascente and Crusciol (2012) reported that the amount of 7.6 Mg ha -1 of B. brizantha and 2.8 Mg ha -1 of millet did not affect soybean plant population. On the other hand, Monquero et al (2010) observed that desiccation done close to the soybean planting day caused reduction in the plant stand.…”

“…Besides, it could be observed that Brachiaria brizantha produced a bigger amount of dry matter in both evaluations (6,547 and 7,968 Mg ha -1 for 15 and 0 days before crop planting) than millet (4,101 and 5,032 Mg ha -1 for 15 and 0 days before crop planting) and common bean (3,937 and 4,424 Mg ha -1 for 15 and 0 days before crop planting). B. brizantha is well-known for producing high amount of biomass that can be used as straw in the no-tillage system (NTS) Nascente and Crusciol, 2012). In NTS, cover crops that produce large amounts of dry matter are desirable to favor a suitable ground cover (Nunes et al, 2006;Nunes et al, 2009;Ferreira et al, 2010).…”

“…On the other hand, Monquero et al (2010) observed that desiccation done close to the soybean planting day caused reduction in the plant stand. Moreover, when the herbicide was applied near the seeding of soybeans, cover crops were not dry enough to allow the straw to be cut by the planter disks (Nascente and Crusciol, 2012). Therefore, the inadequate time to herbicide management could cause a minor seeding efficiency due to the difficulty of cutting and bushing or it might cause initial shadow on the soybean seedling with significant effect in the grain yield (Grisso et al, 2009;Nascente and Crusciol, 2012).…”

“…Such systems are sustainable because of untilled soils and crop rotation that provide permanent maintenance of straw on the soil surface (Sulc and Tracy, 2007;Nascente and Crusciol, 2012;Nascente et al, 2013c). Soybean and corn are the most important cash crops planted in soil under NTS, which is becoming an important kind of soil management practice in Brazil (Conab, 2012).…”

“…The management of cover crops before planting crops is done with total systemic herbicide action, with glyphosate being the most widely used (Nascente and Crusciol, 2012;. This herbicide has broad spectrum of action, normally allowing control of annual and perennial weeds and cover crops (Yamada and Castro, 2007).…”