Comparative Advantage of Narrow Row Spacing and Low Seeding Rate of Soybean Under Semi-Arid No-till Condition.

Drought is the main abiotic factor limiting soybean yield in the semi-arid region of the Northern Great Plains of the USA. There is a lack of information on suitable row spacing and seeding rate of soybean under no-till dryland condition. We hypothesize that narrower row spacing (19 cm) and low seeding rate (36 thousand PLS ha^-1) has comparative advantage over wider row spacing (76 cm) and higher seeding rate (72 thousand PLS ha^-1) in terms of physiology, growth, water use, and yield. Soybean was seeded using an ultra-narrow precision research plot seeder that maintained row spacing of 19, 38, 57, and 76 cm as main plots, and plant population of 36, 48, 60, and 72 thousand PLS ha^-1 as sub-plots. The sub-plot size was 5.5 m X 4.5 m. The findings of treatment effects and their interaction on soil moisture, physiology, growth, and yield of soybean are presented.