Impact of Plant Spacing and Weed Control Treatments on Yield, Quality of Soybean (Glycine Max L.) and Associated Weeds Characters under Middle Egypt Conditions

The present study was carried out on soybean var. Giza 111 atthe Experimental Farm of Faculty of Agriculture, El-Minia University during the summer seasons of 2015 and 2016, to study the impact of plant spacing and weed control treatments on weed control, yield and quality of soybean. The treatments include rows and plant spacing (density) as P1: 60×4cm (175000 plant fed-1), P2: 60×5cm (140000 plant fed-1), P3: 70×4cm (150000 plant fed-1) and P4: 70 × 5cm (120000 plant fed-1) and 10 weed control treatments (W1: Gesagard 50% FW at 1 L fed-1,W2: Fusilade super 12.5%EC at 1 L fed-1, W3: Gesagard 50%FW+ Fusilade super 12.5% EC,W4:Stomp 50%EC at 1.7 L fed-1,W5: Stomp 50%EC + Select-super 12.5% EC at 1 L fed-1, W6: Select-super 12.5%EC, W7: Stomp 12.5%EC+ one hand hoeing, W8: hand hoeing twice, W9: unweeded check and W10: weed free for whole seasons. This study was carried out in a strip-plot design with three replications.  Results showed that increasing of soybean plant density by sowing in the narrow ridge (60 cm) and plant space (4 cm between hills) caused a significant reduction in fresh and dry weight of weeds at 60 days after planting (DAP), compared to wider plant spacing in both seasons. The narrow spacing 60×4 cm led to a reduction in dry weight of total weeds by 26.62 % and 22.90 % and increased soybean seed yield by 5.31% and 4.92% in 2015 and 2016 seasons, respectively. All weed control practices reduced the fresh and dry weight of total weeds, compared to the unweeded check in both seasons. Yield of seeds in unweeded check plots was decreased were about 43.18 and 42.69% due to about 3.5 and 3.3 ton fed-1 fresh weight of total weeds in 2015 and 2016 seasons, respectively, compared to weed free for whole season. Protein and oil% of soybean seeds were decreased by (10.56 and 10.60%) and (18.23 and 18.05%) in 1st and 2nd seasons, respectively due to the weed interference. The interaction effect between plant spacing, 60×4 cm (P1) and weed free followed plant spacing P1 and weed control by Stomp 50%EC + one hand hoeing (W7) gave the best weed control efficiency (WCE) 78.9 and 81.0% in 2015 and 2016 seasons, respectively as well as superior in seed yield of soybean  and net return.