PLANTING TIMES OF COWPEA INTERCROPPED WITH CORN IN THE WEED CONTROL

Abstract

Corn yield losses caused by weeds may reach up to 80%. Reducing the use of herbicides is one of agriculture's major goals and several alternatives are currently being investigated, including intercropping. In the Brazilian Northeast, corn intercropping with cowpea (Vigna unguiculata (L.) Walp.) is extensively practiced, and there is interest in evaluating weed control under this type of intercropping. The objective of this work was to evaluate the effects of different cowpea planting times, intercropped with corn, on green ear yield of two corn cultivars. The experiment was carried out under randomized design blocks with four replications. AG 1051 and AG 2060 corn cultivars were submitted to the following treatments: no hoeing, two hoeings (20 and 40 days after planting), and cowpea planting (BR 4 - Mulato cultivar, with indeterminate growth) at corn planting and at 5, 10, and 15 days later. Twenty-eight weed species were found in the experiment area. In all characteristics evaluated, except for plant height, ear height, and total number of green ears, where no difference occurred between treatments, the lack of weeding determined the smallest means, while weed control determined the highest. In plots where cowpea was sown, intermediate means were obtained for number and weight of marketable unhusked green ears and for number and weight of marketable husked ears. This suggests that cowpea controlled weeds to a certain extent, especially when it is planted earlier, which was, however, insufficient to avoid green ears yield loss. The corn cultivars evaluated were not different among themselves, except with regard to ear height. The cowpea grain yields were practically null in all plots.