晋南地区小麦–玉米轮作体系维持作物高产和土壤磷素水平的适宜施磷量研究

  【目的】  研究维持农作物高产、稳产及土壤磷素肥力的磷肥适宜用量，对于保障国家粮食安全和生态安全具有重要意义。  【方法】  2016—2019年在晋南地区进行磷肥用量田间定位试验，在每个冬小麦–夏玉米轮作周期施N 400 kg/hm2、K₂O 180 kg/hm2的基础上，设置了6个P₂O₅施用水平处理:0、120、180、240、300、360 kg/hm2，氮、磷、钾肥施用量小麦和玉米各占50%，每季作物45%的氮肥和全部磷、钾肥播前一次性底施，55%的氮肥在小麦拔节期和玉米10叶期进行追施。连续3年收获期测产，并测定土壤有效磷含量。  【结果】  不施磷处理(P0)冬小麦–夏玉米轮作体系的产量、效益均最低，土壤有效磷含量逐年下降；施磷显著提高了轮作体系的吸磷量、产量及净收益，3年平均增产23.9%，增收20.4%。冬小麦–夏玉米轮作体系的吸磷量、产量、净收益和施磷量之间的关系均可以用直线平台模型拟合，以该模型计算的冬小麦–夏玉米轮作体系的适宜施磷量为193 kg/hm2，适宜施磷量下的磷肥偏生产力、磷肥农学效率和磷肥利用率分别为115.9 kg/kg、21.9 kg/kg和25.1%。P120和P180处理的土壤有效磷含量呈耗竭状态，土壤有效磷含量年均下降3.0和1.3 mg/kg；P240、P300和P360处理的土壤有效磷含量呈增加状态，土壤有效磷含量年均上升1.5、4.0和4.2 mg/kg，但P300和P360处理间的有效磷含量3年均无显著差异。施磷量和土壤有效磷含量呈显著直线相关，2017、2018和2019年土壤有效磷达到基础土壤水平(Olsen-P 18.5 mg/kg)的施磷量分别为P₂O₅ 192、194和197 kg/hm2。  【结论】  在山西省南部冬小麦–夏玉米轮作区，综合保障作物高产稳产，实现较高磷肥效率和维持土壤初始磷素肥力的年最佳磷肥用量为P₂O₅ 193 kg/hm2。

Optimum phosphorus application rate for maintaining high yield and soil phosphorus fertility under winter wheat–summer maize rotation in Shanxi Province

  【Objectives】  The goal of determining the optimal phosphorus fertilizer application rate was to ensure a high and consistent crop output while maintaining long-term soil phosphorus fertility.  【Methods】  From 2016 to 2019, a field experiment with winter wheat–summer maize rotation system was conducted in the south of Shanxi Province. P₂O₅ at 0, 120, 180, 240, 300, and 360 kg/hm2 per year were the tested P fertilizer application rates. The P fertilizer was evenly divided into two portions in wheat and maize seasons. At harvest, crop P uptake, yield, and soil available P content were measured.  【Results】  P absorption, yield, crop profit, and soil available P content were low when no P was applied (P0). Soil available P content decreased from 18.5 mg/kg in 2016 to 4.0 mg/kg in 2019, with an annual loss of 4.8 mg/kg. From 2017 to 2019, the P application increased yield by 23.9% and profit by 20.4% on average compared to P0. The linear plateau model fit the relationships between P uptake, yield, profit, and phosphorus application rate. The determined optimum P₂O₅ rate was 193 kg/hm2, with partial factor productivity, agronomic efficiency, and phosphorus fertilizer utilization efficiency of 115.9 kg/kg, 21.9 kg/kg, and 25.1%, respectively. Distinct rates of P treatment resulted in different variations in soil available P content. On average, the P120 and P180 treatments reduced soil available P by 3.0 mg/kg and 1.3 mg/kg, respectively, whereas the P240, P300, and P360 treatments increased by 1.5 mg/kg, 4.0 mg/kg, and 4.2 mg/kg, respectively. The P₂O₅ rate that maintained the initial soil P level (Olsen-P 18.5 mg/kg) was P₂O₅ at 192 kg/hm2, 194 kg/hm2, and 197 kg/hm2 based on regression of P application rate and soil available P content.   【Conclusions】  Under the winter wheat and summer maize rotation system in southern Shanxi Province, the optimum yearly P₂O₅ rate for high crop production and profit, relatively high fertilizer efficiency, and preserving initial soil available P content is 193 kg/hm2.