Splitting nitrogen fertilization improves growth, yield and profit of soybean (Glycine max) production in the semi-arid Afghanistan

Abstract

The objectives of this study were to evaluate the effects of splitting application of 30 kg N ha-1 on the growth, yield and economics of soybean (Glycine max var. Dea-won) in the semi-arid and sub-tropical Afghanistan. Besides no-N-fertilization control, urea (30 kg N ha-1) was applied to fields in four-splits: S1, one time basal application at sowing; S2, two-splits of 50% N at sowing and 10 DAS (days after sowing); S3, three-splits of 33% N at sowing, 10 and 20 DAS; and S4, four-splits of 25% N at sowing, 10, 20 and 30 DAS. Aboveground growth and yield parameters were compared at 30, 60, 90 and 127 DAS. Soybean’s growth and yields increased in corresponding with the increased frequency of split fertilization. Three- or four-splits significantly increased plant height, leaf area index, aboveground biomass, crop growth rate, net assimilation rate, relative growth rate, pod and seed numbers, 1,000-seed weight, yield production and economics (gross and net returns and benefit cost ratio) than those at one or two-splits N-application at all these four harvests. Positive relationships were observed among growth parameters and yield traits and yield production. Three- or four-splits at tested N rate and growth stages can meet N requirement for soybean’s growth and yield while improving N use efficiency in semi-arid Afghanistan.