关键词: 紫色土, 稻麦轮作, 长期施肥, 有效磷, 累积磷盈亏, 农学阈值

Abstract:

【Objective】Based on the analyses of soil Olsen-P variation in the purple soil and its effects on crop yield under long-term different fertilizations in the rice-wheat rotation, this paper provided a theoretical basis for efficient and rational P management in purple soil. 【Method】This study were conducted based on the 27-year rice-wheat rotation trial platform in the Purple Soil Fertility Monitoring Station of the national soil fertility monitoring network. The soil Olsen-P content and crop yields of 10 different fertilization treatments were measured and compared, including CK treatment (crops growing without fertilization), N, NP, NK, PK, NPK (treatments with different chemical nitrogen (N), phosphorus (P), potassium (K) fertilizations), and M, NPKS, NPKM, 1.5NPK+M (chemical fertilizer combined with organic manure (M) and straw return (S) treatments) from 1991 to 2018. Then, the plant P uptake per 100 kg grains yield and the recovery rate of P by different fertilizations were calculated and compared, respectively. The responses between soil Olsen-P increment and cumulative P depletion were explored. In addition, the response curve of crop yield to soil Olsen-P content in the purple soil was figured by different modelling methods. The agronomic critical value of Olsen-P content in purple soil was finally calculated. 【Result】Long-term application of P fertilizer could significantly increase soil Olsen-P content. The average annual increment of soil Olsen-P content was 0.80-2.32 mg·kg^-1 in P application treatments, whereas the soil Olsen-P content of CK, N, NK and M treatments decreased year by year to a steady state. The cumulative P surpluses by the 27-year P application treatments were 244.8-698.2 kg P·hm^-2, among which the cumulative P surplus of the 1.5NPK+M treatment was the highest. A significant linear correlation between cumulative soil P surplus and soil Olsen-P increment could be found in P application treatments. In detail, soil Olsen-P increased by 4.27-6.5 mg·kg^-1with 100 kg·P·hm^-2 cumulative surplus in P application treatments. Fertilization could significantly increase crop yields and P uptake in the long-term rice-wheat rotation system. The plant P uptake per 100 kg rice yield was 0.17-0.41 kg, whereas the plant P uptake per 100 kg wheat yield was 0.25-0.57 kg. The utilization rates of P under all treatments were 10.3%-39.7%. Four models (linear-platform model, linear-linear model, BoxLucas model, and Michelice model) were good for fitting the response of crop yield to Olsen-P content in purple soil. The agronomic critical value of Olsen-P content in purple soil of rice and wheat calculated by linear-linear model (with the highest R ²) were 13.28 mg·kg^-1 and 9.93 mg·kg^-1, respectively. 【Conclusion】Appropriate application of P fertilizer could significantly improve the P uptake of crop in rice-wheat rotation system on purple soil, crop yields and soil available P content. The linear-linear model was recommended to calculate the critical value of Olsen-P content in purple soil under rice-wheat rotation system. Application rates of P fertilizer should be adjusted timely according to the difference between actual soil Olsen-P content and agronomic critical value of Olsen-P content in productivity.

Key words: purple soil, rice-wheat rotation, long-term fertilization, Olsen-P content, total P balance, agronomic critical value of Olsen-P