Weed dynamics in grain sorghum-grass intercropped systems

Joilson Sodré Filho,Robélio Leandro Marchão,Arminda Moreira De Carvalho,Ricardo Carmona

doi:10.1590/s1806-66902014000500019

Abstract

The aim of this study was to assess the influence of short-season sorghum-grass intercropped systems on weed population dynamics. The integrated systems consisted of sorghum grown at two row spacings (0.50 m and 0.70 m), intercropped with palisade grass or Congo grass. We also used sole crops of sorghum, palisade grass, Congo grass and a fallow to serve as a reference for spontaneous vegetation. The experiment was conducted in 2010 and 2011 at Planaltina (Federal District) in Brazil. Weed populations and weed dry matter were assessed during the short season and during the succession soybean cycle. The weed soil seed bank was sampled in both years of the study. Sorghum at a row spacing of 0.50 m intercropped with Congo grass reduced the Ageratum conyzoides population. The Tridax procumbens seed bank in the soil was reduced by using sorghum at a the row spacing of 0.70 m, whether intercropped or not. Planting palisade grass during the short season reduced Digitaria sanguinalis in the soil seed bank. Planting palisade grass or Congo grass as a sole crop or intercropped reduced the number of weed seeds in the soil, showing that these species can be recommended for integrated weed management in intercropped systems.

Highlights

One of the most serious problems in intensive tropical agriculture, especially under no-tillage, is the presence of weed species that are difficult to manage
Planting palisade grass during the short season reduced Digitaria sanguinalis in the soil seed bank
In all the assessment we identified 22 weed species, as follows in decreasing order of occurrence: Bidens pilosa (22.39%), Chamaesyce hirta (14.60%), Richardia brasiliensis (12.41%), Ageratum conyzoides (6.34%), Eleusine indica (4.55%), Digitaria sanguinalis (4.49%), Tridax procumbens (3.70%), Emilia fosbergii (3.60%), Gnaphalium spicatum (2.57%), Rhynchelytrum repens (2.19%), Commelina benghalensis (0.99%), Galinsoga parviflora(0.91%),Conyzabonariensis (0.40%),Brachiaria decumbens (0.29%), Euphorbia heterophylla (0.18%), Amaranthus deflexus (0.14%) and Oxalis corniculata (0.09%)

Summary

Introduction

One of the most serious problems in intensive tropical agriculture, especially under no-tillage, is the presence of weed species that are difficult to manage. Controlling weeds when sowing crops after desiccation can be important in maintaining crop competitiveness. This kind of control is efficient only for weeds that are already established, allowing new weeds to emerge during the crop cycle. Silva et al (2009) observed reductions of up to 73% in soybean yields due to the presence of weeds during the entire crop cycle. One way of keeping weed populations below the level at which economic damage results is to use the crop itself, leaving crop residues on the soil surface, a strategy for reducing weed populations rather than eliminating weed species altogether

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Results