Legacy phosphorus in calcareous soil under 33 years of P fertilizer application: Implications for efficient P management in agriculture

Abstract

AbstractPhosphorus (P) fertilizers have long been applied in agriculture. However, the influence of long‐term P addition on the evolution of soil P fertility and legacy P characteristics have not been well‐documented. Herein, literature data were collected from the Chinese National Knowledge Infrastructure Database (CNKI) to explore the evolution of soil P fertility after 33 years of application of P fertilizer; different soil samples were collected from cropland and adjacent uncultivated land to analyse the distribution of P fractions at different soil depths (0–0.8 m) using Guppy's sequential P extraction method. We found that soil Olsen‐P significantly increased by 3.6‐fold (from 7.2 mg kg−1in 1981 to 25.9 mg kg−1in 2013) after 33 years of P application, while total P increased slightly. The ratios of inorganic P fractions in cropland to those uncultivated land followed NaHCO3‐P (1.47) > NaOH‐P (1.38) > resin‐P (1.37) > residue‐P (1.17) > HCl‐P (1.11), suggesting that long‐term P addition contributed more to labile and moderately labile P rather than non‐labile P. Moreover, a principal component analysis could distinguish between cropland and uncultivated land, indicating that long‐term application of P fertilizer changed soil P characteristics. Compared to uncultivated land, soil NaHCO3‐P in cropland was closely associated with soil organic C, total nitrogen and carbonate. Collectively, our findings highlight that soil legacy P was notably increased after long‐term of P application, and a large portion of the applied P remained in labile and moderately labile forms. Therefore, soil legacy P can be recommended as a useful P management tool.