基于旱地小麦高产优质的氮肥用量优化

  【目的】  探讨长期定位施氮条件下小麦产量与籽粒养分含量的变化，及土壤硝态氮、有效磷和速效钾的变化，为旱地小麦合理施用氮肥，保持土壤肥力，提高产量和改善品质提供理论依据。  【方法】  本研究基于2004年在黄土高原开始的长期定位施肥试验，2015—2017连续3年取样，研究了施氮量对土壤硝态氮、有效磷、速效钾含量，小麦氮磷钾素吸收利用，籽粒氮、磷、钾含量，地上部生物量、籽粒产量及其构成的影响。  【结果】  与不施氮相比，长期施氮小麦平均增产67.1%，生物量提高52.0%，收获指数提高9.5%；穗数和穗粒数平均分别提高32.5%和40.0%，千粒重下降7.1%。施氮量与产量、生物量呈抛物线关系，获得最高产量6587 kg/hm2的施氮量为N 215 kg/hm2。籽粒氮含量随施氮量增加而增加，磷含量降低，钾含量变化较小。土壤硝态氮含量与施氮量呈显著正相关，小麦获得最高产量时播前和成熟期硝态氮含量分别为7.2和10.3 mg/kg；有效磷含量随施氮量增加而降低，速效钾含量变化较小。氮收获指数、生理效率、偏生产力、农学效率均随施氮量增加而降低。  【结论】  综合考虑小麦的籽粒产量和籽粒关键养分含量，研究区域旱地冬小麦产量目标应为6300 kg/hm2，施氮量为N 150 kg/hm2、施磷量为P₂O₅ 100 kg/hm2，播前或收获期表层 (0—20 cm) 土壤硝态氮保持在6.0～8.0 mg/kg、土壤有效磷12.0～15.0 mg/kg、土壤速效钾139～140 mg/kg。

Optimization of nitrogen rate based on grain yield and nutrient contents in dryland wheat production

  【Objectives】  It is of great significance to explore the wheat grain yield, soil nitrate nitrogen (N), available phosphorus (P), available potassium (K) and grain nutrient contents under the condition of a long term N application at different rates, for the purpose of appropriate N application, soil fertility improvement, wheat yield increase and grain nutritional quality improvement in drylands.  【Methods】  Field experiments were conducted to investigate the effects of different N rates on soil nitrate N, available P and K contents, N, P and K absorption and utilization of wheat, grain N, P and K contents, wheat biomass, yield and yield components based on the long-term location-fixed field experiment, which was initiated in 2004 in the Loess Plateau. Soil and plant samples were collected in the consecutive experimental years of 2015–2017.  【Results】  The three-year averaged results showed that long-term application of N increased wheat grain yield by 67.1%, biomass by 52.0%, harvest index by 9.5%, spike number by 32.5% and grains per spike by 40.0%, respectively, while the 1000-grain weight was decreased compared with no N application. The grain wheat yield and biomass were quadratically correlated with the N rate, and the maximum yield was 6587 kg/hm2 obtained at a N rate of N 215 kg/hm2. The P content of grain decreased with the N rate increase, K content of grain showed no significant change, while the N content showed an opposite trend. There was a significant positive correlation between the soil nitrate N content and the N application rate. The soil nitrate N content was 7.2 mg/kg at sowing and 10.3 mg/kg at harvest when the maximum yield was obtained. Soil available P decreased with the N application rate increase, and soil available K showed no significant change. The N absorption and utilization efficiencies (i.e. N harvest index, N physiological efficiency, N partial factor productivity and agronomic efficiency) decreased with the increase of N rates.  【Conclusions】  For improving the winter wheat grain yield and grain key nutrient contents, the target grain yield should be 6300 kg/hm2 in drylands of the experimental area, and the corresponding fertilizer application rate should be kept at N 150 kg/hm2 and P₂O₅ 100 kg/hm2, and the nitrate N would be sustained at 6.0–8.0 mg/kg in 0–20 cm soil at sowing or harvest, respectively, and available P be kept at 12.0–15.0 mg/kg, and available K at 139–140 mg/kg.