Planting density of gliricidia when intercropped with corn for weed control

Abstract

Reduced use of herbicides that cause environmental pollution problems is of great interest in modern agriculture. Soil mulching with gliricidia (Gliricidia sepium) branches does not have an allelopathic effect on corn, but decreases weed populations. The objective of this study was to evaluate the effects of gliricidia planting density, when grown as an intercrop, on weed control and corn yield parameters. A randomized block design with split-plots and ten replicates was adopted. Corn cultivars AG 1051 and BM 3061 were grown without hoeing, with two hoes (at 24 and 44 days after planting), and intercropped with gliricidia (planted simultaneously with corn, between crop rows, using two seedlings/pit, spaced at 30, 40, or 50 cm). Twenty-one weed species were found in the experimental area. Increased gliricidia planting density reduced weed biomass, but no difference was found between weed biomass in the intercrop and weed biomass in non-hoed corn. Gliricidia intercropped with corn, planted at a row spacing of 30 cm, did not significantly differ from hoed corn in most characteristics considered to evaluate green corn yield, although mean values were smaller. As to the number and weight of marketable green ears, reductions of 5% and 13%, respectively, were observed. Intercropping caused a 17% reduction in grain yield, reducing the losses (36%) observed in non-hoed corn by more than 50%. The highest green ear yield and grain yield values were obtained with two hoeings, while the lowest values were observed for non-hoed corn. The cultivars did not differ regarding green ear yield and grain yield.

Weed control in corn and weed sample size for growth evaluations

“…Often, this is not observed. Linhares et al (2009), for example, verified differences between weed control methods on corn yield, but did not see effects of those methods on weed control. Such occasional lack of "parallelism" between the effects on both characteristics (crop yield and weed growth) may be associated with the small sample sizes used in weed growth evaluation.…”

“…This implies small experimental precision; consequently, no differences can be detected between weed control methods on growth of those plants. Linhares et al (2009) It can be concluded that "two hoeings [at 20 and 40 days after corn sowing (DACS)] (treatment A)" provided the best baby corn, green corn, and grain yields. The treatment represented by "hoeing at 20 DACS + gliricidia after hoeing (treatment B)" did not differ from treatment A with regard to yield for the three products and was equivalent to the "gliricidia at corn + hoeing at 40 DACS" treatment for green corn yield, but it was superior to it for baby corn weight and grain yield.…”

“…In one such study, gliricidia was grown between corn rows and partially controlled weeds (Silva et al, 2009). Several other studies, in which broadcasting sowing of gliricidia was performed between corn rows (Linhares et al, 2009, Silva et al, 2010a, confirmed that gliricidia partially controls weeds in corn, with benefits on green ear yield and corn grain.…”

Controle de plantas daninhas na cultura do milho com gliricídia em consorciação

“…Além disso, há indícios de que ocorre o "pegamento" de algumas plantas daninhas após as capinas (Silva et al, 2010a). Resultados semelhantes a esses foram observados por outros autores (Linhares et al, 2009;Silva et al, 2009b), que também estudaram o consórcio milho-gliricídia visando ao controle de plantas daninhas.…”

“…Portanto, das 25 sementes viáveis de gliricí-dia semeadas, apenas 28% deram origem a plantas que sobreviveram até o final do ciclo do milho. Essa redução na população de plantas de gliricídia foi observada por outros autores (Linhares et al, 2009) e pode ser atribuída a vários fatores, incluindo a supressão, em razão da competição interespecífica com o milho e plantas daninhas, além de outros fatores ambientais que usualmente reduzem o estande das culturas (ataque de pragas, profundidade de semeadura inadequada, etc. ).…”