ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 69 Number 3
Weed management in a low-input cropping system in the Peruvian Amazon region
A weed-control study in a five-crop sequence [rice-rice-cowpea-rice-cowpea] following forest clearing of a Typic Paleudult in the Peruvian Amazon had the following objectives: (1) to determine the magnitude of the weed problem during the transition from secondary forest to continuous cropping; (2) to measure the effect of weed infestation on crop yields; and (3) to test cultural practices that could form the basis of a weedmanagement programme for a continuously cropped, low-input system. Tillage and residue mainplot treatments were: (1) rototill with previous crop residues incorporated; (2) rototill with residues mulched; and (3) no-till with residues mulched. A factorial arrangement of two crop planting densities (high and low) and three weed control practices (hand weed, herbicide and no control) comprised the subplot treatments. Tilled plots had more weeds than untilled in the first crop but fewer in the fifth. Mulching residues had little weed-controlling effect, and crop yields were always higher when residues were incorporated. High planting density reduced weed levels and increased crop yields. Herbicides were as effective as hand weeding in controlling weeds, but herbicide costs sharply limit their use in low-input systems. Rice yields fell by 54-100% in the absence of weed control but were reduced by less than 30% for cowpea. Sedges comprised 84% of the weeds in the first crop following forest clearing, but grasses dominated (79%) in the fifth crop.
Keywords: Weed management; Herbicides; Mulches; Planting density; Shifting cultivation; Forest clearing; Peruvian Amazon