Growth and yield responses of soybean according to subsurface fertigation

Abstract

To increase soybean [Glycine max (L.) Merr.] yield, appropriate amounts of water and fertilizer are required at optimal times from sowing to maturity. This study was conducted to investigate how soybean growth and yield were affected by irrigation and fertigation using a subsurface drip system, which consisted of a buried (40-cm underground) drip pipe that can be used in a semipermanent manner without affecting agricultural work on the ground. The amount of water required for the fertigation treatment was determined to be 176 t ha(-1) with the sandy loam soil in this experimental field. Fertigation treatments based on 176 t ha(-1) were carried out as topdressing applications and were applied through the subsurface drip system based on the fertilizer concentration (nitrogen only: N 20, N 40, N 60 kg ha(-1), or compound fertilizer, that is, NPK 1/2 [half of the standard fertilizer amount applied as 16-16-18]). The other treatments included irrigation only and control (nontreatment). The results indicated that the N 20 treatment was the most effective, increasing yield by 83% compared with the control, whereas the N 40, N 60, and NPK 1/2 treatments produced slightly lower yields. In terms of fertigation, an excessive fertilizer concentration increased the growth of aboveground parts but reduces nodulation and yield. These results highlight the effectiveness of fertigation as a form of topdressing fertilization using a subsurface drip system for achieving a high yield and stable soybean production.