Combining rhizosphere and soil-based P management decreased the P fertilizer demand of China by more than half based on LePA model simulations

Phosphorus (P) is a finite natural resource and is increasingly considered to be a challenge for global sustainability. Agriculture in China plays a key role in global sustainable P management. Rhizosphere and soil-based P management are necessary for improving P–use efficiency and crop productivity in intensive agriculture in China. A previous study has shown that the future demand for phosphate fertilizer by China estimated by the LePA model (legacy phosphorus assessment model) can be greatly reduced by soil-based P management (the building-up and maintenance approach). The present study used the LePA model to predict the phosphate demand by China through combined rhizosphere and soil-based P management at county scale under four P fertilizer scenarios: (1) Same P application rate as in 2012; (2) rate maintained same as 2012 in low-P counties or no P fertilizer applied in high-P counties until targeted soil Olsen-P (TPOₗₛₑₙ) level is reached, and then rate was the same as P-removed at harvest; (3) rate in each county decreased to 1-7 kg ha⁻¹ yr⁻¹ after TPOₗₛₑₙ is reached in low-P counties, then increased by 0.1-9 kg ha⁻¹ yr⁻¹ until equal to P-removal; (4) rate maintained same as 2012 in low-P counties until TPOₗₛₑₙ is reached and then equaled to P-removal, while the rate in high-P counties is decreased to 1-7 kg ha⁻¹ yr⁻¹ until TPOₗₛₑₙ is reached and then increased by 0.1-9 kg ha⁻¹ yr⁻¹ until equal to P-removal. Our predictions showed that the total demand for P fertilizer by all China was 693 Mt P₂O₅ and according to scenario 4, P fertilizer could be reduced by 57.5% compared with farmer current practice, during the period 2013-2080. The model showed that rhizosphere P management led to a further 8.0% decrease in P fertilizer use compared with soil-based P management. The average soil Olsen-P level in China only needs to be maintained at 17 mg kg⁻¹ to achieve high crop yields. Our results provide a firm basis for government to issue relevant policies for sustainable P management in China.