EFFECT OF COMPETITIVE ABILITIES OF SOME SOYBEAN GENOTYPES, PLANT DENSITIES AND WEED CONTROL TREATMENTS ON SOYBEAN (GLYCINE MAX L.) AND IT'S ASSOCIATED WEEDS.

Abstract

Two field experiments were conducted during the two successive seasons of 2013 and 2014 at Sakha Agricultural Research Station, to evaluate the efficiency of plant densities, genotypes and weed control treatments on soybean and associated weeds. Split- split plot design with four replications was used. The main plots included three plant densities (168000, 144000 and 120000 plants/ fed), the sub plots included two soybean genotypes (Giza 111 and Toano). Meanwhile, the sub-sub plots included six weed control treatments (prometryne at 1.0 L/fed; pendimethalin at 1.5 L/fed) plus one hand hoeing; (prometryne and pendimethan) followed by fluzifop-p-buty at of 1.0 L/fed, hand hoeing twice and unweeded control treatment. Results showed that increasing plant density reduced dry weight of broad- leaved, grassy and total weeds under combined, reduced dry weight of broad- leaved, grassy and total weeds by 26.4, 27.9 and 26.9%, to Toano. However, Giza 111 suppressed the growth of broad- leaved, grassy and total weeds by 28.7, 24.7 and 27.3%, respectively, and increased soybean seed yield by 6.67%. All weed control treatments reduced dry weight of broad-leaved, grassy and total weeds as compared with control treatment. Yield losses under control treatment were estimated by 39.66% as compared with prometryne/ one hand hoeing treatment. Seed yield (ton/fed) was positively correlated with yield components and negatively correlated with most weeds in combined analysis. Thus, weed control of soybean depended on weed control integrated in this crop. Whereas plant density reduced the weeds by 26.9%, genotypes by 27.3% and prometryne/one hand hoeing by 89.8%. Meanwhile, the integration between such factors as plant density, genotypes and weed control treatments reduced the weeds by 94.0%.