Phosphorus leaching risk from black soil increased due to conversion of arid agricultural land to paddy land in northeast China

Abstract

BackgroundLand-use change from arid agricultural land to paddy land may increase soil phosphorus (P) leaching in the black soil region. However, little information is available for soil P leaching risk assessment from soil profiles due to the land-use conversion in the black soil region of northeast China.ResultsThis study explored the effect of land-use change from arid agricultural land to paddy land on soil P leaching change point, P leaching risk and P fractions. Conversion from arid agricultural land to paddy land decrease soil P leaching change point (0–20 cm: 59.63 mg kg−1 vs. 35.35 mg kg−1; 20–40 cm: 24.31 mg kg−1 vs. 17.20 mg kg−1; 40–60 cm: 32.91 mg kg−1 vs. 10.45 mg kg−1); 30.9% of arid agricultural soils were at risk of P leaching into the shallow groundwater, compared to 87.5% of paddy soils, implying a high risk of P leaching after land-use conversion. P fraction analysis using the Hedley sequential extraction method showed that moderately active P, including NaOH-Pi, NaOH-Po, and HCl-Pi, were the dominant fractions in the tested soils. HCl-Pi and NaOH-Pi were the major P fraction of moderately active P in arid agricultural land and paddy land, respectively, indicating that land-use change leads to the conversion from Ca-bound P to P associated with Fe and Al.ConclusionsThe soil P leaching change point decreased due to land-use conversion from arid agricultural soils to paddy soils, which may lead to higher P leaching risk. Therefore, it is necessary to strengthen the management and control of soil P loss in areas with large-scaled conversion from arid agricultural land to paddy fields.Graphical