Sustainable phosphorus (P) management: Impact of low P input with enhancement measures on soil P fractions and crop yield performance on a calcareous soil

The continuous supply of phosphorus (P) is indispensable in crop production. However, P resources are non-renewable, and environmental concerns like eutrophication associated with its loss from agroecosystems make the sustainable management of P resources essential for ensuring global food security. This study was designed to reduce mineral P inputs through management practices. A field experiment comprising a wheat–maize rotation system was conducted in the Guanzhong Plain of Shaanxi Province, China from 2018–2023. The eight treatments included CK (without P), FP (conventional P application); RP (recommended P); RP₈₀ (20% reduction in RP); SRP₈₀ (20% reduction in RP with straw wrapping); ARP₈₀ (20% reduction in RP with ammonium sulfate instead of urea); SARP₈₀ (20% reduction in RP with straw wrapping and ammonium sulfate instead of urea); and SARP₆₀ (40% reduction in RP with straw wrapping and ammonium sulfate instead of urea). Crop yield, P uptake, and P fertilizer use efficiency were measured during harvest and throughout the entire period of the study. At the end of the experiment, P fractions were estimated using the Tiessen-Moir P classification method. The results revealed that the grain yields of all the treatments except for RP₈₀ were significantly increased compared to CK, with increases of 14.9–28.8%. Furthermore, agronomic efficiency, apparent P use efficiency, P recovery rate, and partial factor productivity were significantly improved for the treatments that received 20% less P with straw wrapping. Moreover, the enhancement measures significantly increased labile and moderately labile P in the soil. Therefore, straw wrapping with ammonium sulfate instead of urea is one of the most effective ways to reduce mineral P inputs while increasing the efficiency of P in wheat–maize rotation systems.