Spatial-temporal evolution characteristics and driving factors of partial phosphorus productivity in major grain crops in China

  Objectives  In the last 30 years, there are various fertilization regimes in upland and paddy-upland rotation systems in China, and the variation of soil phosphorus (P) status in different regions was great. The objective of this study was to analyze the spatio-temporal characteristics and driving factors of P surplus and partial factor productivity of P (PFPP) in each region, and to provide theoretical guidance for scientific management of P fertilizer.

  Methods  Based on the long-term monitoring database (1988 to 2019), data were cited from a total of 829 upland and paddy-upland rotation monitoring sites for comparison and summarization in six regions (i.e. Northeast of China (NE), North of China (NC), Yangtze River Delta (YRD), Middle Reaches of the Yangtze River (MYR), Northwest of China (NW) and Southwest of China (SW)). The P fertilizer application rate, PFPP, P balance and the main driving factors of PFPP and P balance were analyzed, and the recommended P application rate in each region was further determined.

  Results  The average application rate of P fertilizer and PFPP were 137.7, 109.2, 75.13 kg/hm² and 61.99, 130.1, 158.9 kg/kg in wheat, maize and rice cropping system in upland and paddy-upland rotation in China, respectively. The application rate of P fertilizer (213.7 and 184.0 kg/hm²) and P surplus (157.9 and 51.55 kg/hm²) in wheat and maize in NW were the highest, and the P surplus accounted for 73.9% and 28.0% of the P application rate, respectively. In the maize season, the value of P balance in NE, NC and YRD were deficient, and the amount of deficiency were 25.29, 11.38 and 14.57 kg/hm², respectively. In the rice season, the application rates of P fertilizer were consistent with P output in YRD and SW. The PFPP in NE, NC and MYR increased significantly with the cultivation years from 1988 to 2012, and began to be stable after 2013. In the YRD and SW, the PFPP decreased at first and increased later, and the turning points were in 2002 and 2007, respectively. In NW, the PFPP increased continuously after 30 years of fertilization. The soil type, organic matter content and cropping system were the main influencing factors of P surplus and PFPP in NE, MYR, and NW, respectively. The regional differences of P surplus and PFPP were mainly affected by the application rate of P fertilizer and crop type.

  Conclusions  Excessive P application in wheat season has resulted in a large amount of P surplus in each region, and the application rates of P fertilizer were consistent with P output in maize and rice season in China. In addition, there were significant regional differences in the temporal variation and driving factors of phosphorus balance and PFPP. Considering the PFPP and the driving factors of each region, the recommended P fertilizer application rates in NC, MYR, YRD, SW and NW in wheat season were 64.42, 37.59, 60.11, 35.22 and 53.55 kg/hm², respectively. In NE, NC, MYR, YRD, SW and NW, the recommended rates of P fertilizer in maize season were 129.5, 97.11, 83.85, 80.60, 80.09 and 131.9 kg/hm², respectively. While in MYR, YRD and SW, the recommended P application rates were 62.12, 76.32 and 64.03 kg/hm², respectively.