Cowpea plant population under irrigation regime

Abstract

Two experiments were carried out under a sprinkle irrigation condition in alluvial eutrophic soil in Teresina, PI, Brazil, in 1993 to evaluate the productive behavior of erect and spreading cowpea (Vigna unguiculata (L.) Walp.), at different plant populations. One factorial schedule (3 x 6) in a randomized block with four replications was used. The spreading cultivars studied were BR 14-Mulato, BR 7-Parnayba and BR 10-Piauí, in a population of 2.5; 5.0; 7.5; 10.0; 12.5 and 15.0 plants.m^-2. The erect cultivars were BR 12-Canindé, Vita 7 and IT 82D-784, combined with a population of 3.33; 6.67; 10.00; 13.30; 16.67 and 20.00 plants.m^-2. There was no interaction between cultivar x plant population in both experiments, showing that, the performance of cultivars planted do not depend on plant populations. The average grain productivity for the spreading cultivars (2,149 kg.ha^-1) and for the erect cultivars (2,389 kg.ha^-1) did not depend on plant population; however, the erect cultivars produced 11.2% more grain than spreading cultivars. The Vita 7 and BR 14-Mulato, presented the best water efficiency, 9.4 kg.ha^-1.mm^-1 and 7.1 kg.ha^-1.mm^-1, respectivelly. In general, the production component more affected by the plant population was pod number, and grain weight by plant, that decreased when the plant number by area increased.