AbstractKaki and 28-Bushy pigeon peas were grown in the southern plains of Puerto Rico, in four spatial arrangements with six intervals of weed competition during two growing seasons to determine the influence of weed competition on crop growth, development and yield. In both growing seasons, Cleome gynandra, Amaranthus dubius, Echinochloa colona, Leptochloa filiformis, and Digitaria sanguinalis were the dominant weeds. C. gynandra and E. colona dominated the early weed flora until approximately 40 days after pigeon pea emergence. Later, weed flora was dominated by L. filiformis, D. sanguinalis, and A. dubius. The presence of weeds during early growth stages reduced initial crop growth and delayed differentiation including flowering of the two pigeon pea cultivars. Elimination of weeds at or before 21 to 28 days after pigeon pea emergence and thereafter, generally resulted in the recovery of pigeon pea plants and prevented measurable losses in final yield. The critical period for removing weeds in pigeon peas appeared to vary between the pigeon pea cultivars and between the two growing seasons. In the May 6 planting, pigeon pea yields were reduced after 28 and 21 days of early competition for Kaki and 28-Bushy, respectively. In the July 1 planting, however, losses occurred at 21 and 14 days of weed competition for the two respective cultivars. No differences were found in weed numbers or yield between the two cultivars or among spatial arrangements in either planting season. However, weed number and yield were greater during the first planting season compared with those of the second. Planting pigeon peas under short photoperiods accelerated vegetative growth, shortened the total cropping cycle, and resulted in reduced yield and total growth for both cultivars. Losses from early weed competition occurred earlier under the short-day planting than those under the long-day planting.
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