Influence of phosphorus fertilization on input-cost relationship and crop efficiencies of soybean (Glycine max) in Kandahar, Afghanistan

A field experiment was conducted during the spring season of 2017, at the Afghanistan National Agricultural Science and Technology University, Kandahar, Afghanistan, to evaluate the effects of phosphorus fertilization on yield parameters, input-cost relationships and use-efficiency in soybean [Glycine max (L.) Merr.]. Six phosphorus fertilization treatments, viz. control (no P), 15 kg P₂O₅/ha, 30 kg P₂O₅/ha, 45 kg P₂O₅/ha, 60 kg P₂O₅/ha and 75 kg P₂O₅/ha, were applied in 4 replicates. The highest seed yield (2.47 t/ha) was recorded with the application of 75 kg P₂O₅/ha, the increase being ∼34.3% over the control (no phosphorus). Similarly, cost of cultivation increased with increasing rate of phosphorus (P), 75 kg P₂O₅/ha was the costliest treatment among the treatments. Application of 75 kg P₂O₅/ha resulted in the highest gross (163.9 × 10³ /ha) and net returns (84.90 × 10³ /ha) followed by 60 kg P₂O₅/ha, however, the maximum benefit: cost ratio was recorded with 60 kg P₂O₅/ha. Further, the highest production (19.5 kg grain/ha/day) and monetary (763.8 /ha/day) efficiencies were recorded with the 75 kg P₂O₅/ha. Similarly, application of 30 kg P₂O₅/ha showed the highest agronomic efficiency (15.4 kg grain increased/kg P₂O₅ applied/ha). Overall, P fertilization had positive effect on nodulation which in turn reflected in yield and also influenced production efficiencies.