Effect of P fertilizer reduction regime on soil Olsen-P, root Fe-plaque P, and rice P uptake in rice-wheat rotation paddy fields

Abstract

In agricultural systems, it is vital to use limited yet optimal phosphorus (P) resources, because excessive P fertilizer application leads to the accumulation of P in soil, increasing the risk of environmental pollution and causing the waste and exhaustion of P resources. In a rice-wheat rotation system, omitting P fertilizer application in the rice-growing season is a good alternative; however, how this P fertilization reduction influences changes in P in the soil-root-aboveground system is unclear. In this study, after a seven-year rice-wheat rotation at the Yixing (YX) and Changshu (CS) sampling sites, China, compared with P fertilization in rice- and wheat-growing seasons (PR+W), reduced P fertilization (no P fertilizer application in either season, P0; P fertilization only in wheat-growing seasons, PW; and P fertilization only in rice-growing seasons, PR) did not result in substantial variation in crop biomass. The PW treatment did not reduce crop total P, root iron (Fe)-plaque P, and soil Olsen-P at three stages of rice growth (seedling, booting, and harvesting stages) at the YX and CS sites. In contrast, concentrations of soil Olsen-P, aboveground crop total P, and root Fe-plaque P decreased in the P0 treatment by 45.8%–81.0%, 24.6%–30.9%, and 45.6%–73.4%, respectively. In addition, a significant negative correlation was observed between the root Fe-plaque P and crop biomass at the two sites. Significant positive correlations were also observed between root Fe-plaque P and root total P, crop total P, and soil Olsen-P. In addition, the results of a redundancy analysis revealed that soil alkaline phosphatase (ALP) played a major role in the supply of P in soil, and was closely associated with root Fe-plaque P. The results of this study will enhance the understanding of the changes in P in the soil-root-aboveground system, particularly under P fertilizer reduction regimes.