Effect of weed control treatments and hill-spacing on soybean and associated weeds

Abstract

Two field experiments were carried out at the Experimental Farm of Assiut University, during the 2000 and 2001 summer seasons, to study the effect of three hill spacings (5, 10 and 15 cm) and six weed control treatments on the associated weeds, plant growth, yield and quality of soybean. The weed control treatments were carried out with trifluralin, linuron, pendimethalin, bentazon and hand hoeing, with an unweeded treatment as the control. All the weed control treatments exerted a significant influence on the dry weight of weeds. Hand hoeing and pendimethalin treatment significantly decreased the dry weight of dicot and monocot weeds as compared to the unweeded treatment. Hand hoeing gave the lowest value of the dry weight of total weeds and the highest efficiency percentage. In general, the significantly lowest dry weight of total weeds was recorded for densely sown soybeans. The weed control treatments exerted a significant influence on all the characters under study (plant height, weight of pods and seeds/plant, number of plants at harvest, seed yield/ha). The height of the first pod was lowered by hand hoeing and the application of pendimethalin increased the number of pods/plant, while the highest values of number of branches/plant, seed index, oil and protein contents were obtained after linuron application. wider spacing produced higher values for the number of pods and branches/plant, weight of pods and seeds/plant, seed index and protein content and lowered the height of the first pod as compared to plants sown at closer spacing. The latter produced the highest values of number of plants/ha, seed yield/ha and oil content at harvest. The first order interaction exerted a significant influence on all the characters studied, the highest seed yield/ha (2728.6 kg) being obtained from sowing plants at 5 cm combined with hand hoeing.