施肥措施对水旱轮作条件下灌淤土磷素形态的影响

  目的  研究水旱轮作条件下灌淤土磷素形态的变化特征，为宁夏引黄灌区作物施肥调控土壤磷素有效性提供科学依据。  方法  在水稻-玉米轮作体系下，设不施氮肥（T0）、常规施肥（T1）、优化施氮（T2）、70%优化施氮 + 30%有机肥氮（T3）、80%优化施氮 + 20%有机肥氮（T4）、秸秆还田 + 70%优化施氮 + 30%有机肥氮（T5）、秸秆还田 + 80%优化施氮 + 20%有机肥氮（T6）7个试验处理，通过田间小区定位试验研究了不同施肥措施对灌淤土全磷、速效磷和无机态磷含量的影响。  结果  在水旱轮作过程中，不同施肥措施对各季作物土壤全磷含量和旱地玉米速效磷含量影响不明显，但秸秆还田配施化肥和有机肥（T5、T6）能提高耕层土壤速效磷含量，水稻季和玉米季最高含量分别达56.4 mg kg?1和40.4 mg kg?1。由水田改为旱作后，不同施肥措施下土壤速效磷含量平均降低了7.6 ~ 18.1 mg kg?1。水田条件下不同施肥措施对无机磷含量均有显著影响（铝结合态磷除外）；旱作条件下不同施肥措施对铝结合态磷、铁结合态磷、闭蓄态磷含量均有显著影响，但对交换态磷、钙结合态磷含量影响不大。水田或旱作条件下，闭蓄态磷和钙结合态磷都是灌淤土无机磷的主要赋存形态。  结论  在宁夏引黄灌区水旱轮作体系下，有机无机肥配施秸秆还田是灌淤土磷素有效化调控的最有效手段，且在水稻季的调控效应最明显。

Effects of Different Fertilization Methods on Phosphorus Forms in Irrigation Silting Soils in the Rotation of Paddy Rice and Maize

  Objective  The paper aims to study the characteristics of phosphorus (P) forms in irrigation silting soils in the rotation of paddy rice and maize, and in order to provide the scientific basis for crop fertilization regulating on soil P availability in the Yellow River Irrigation Region in Ningxia.   Method  In the paddy rice and maize rotation system, 7 fertilizer treatments were designed as: no nitrogen (N) application (T0), conventional fertilization (T1), optimized N application (T2), 70% optimized N application + 30% organic N application (T3), 80% optimized N application + 20% organic N application (T4), straw incorporation + 70% optimized N application + 30% organic N application (T5), and straw incorporation + 80% optimized N application + 20% organic N application (T6). A location field plot experiment was carried out to investigate the effects of different fertilization methods on total P, available P (Olsen-P) and inorganic P contents in irrigation silting soils.   Result  During the rotation of paddy rice and maize, there were no significant effects on soil total P contents in each crop season and available P contents in dry land maize under different fertilization methods. However, topsoil available P contents were improved by 56.4 mg kg?1 and 40.4 mg kg?1 with straw incorporation and meanwhile combination application of chemical and organic fertilizers (treatments T5, T6) in paddy rice and maize, respectively. Transforming paddy field into dry land, soil available P contents were decreased by 7.6-18.1 mg kg?1 under different fertilization methods. There were significantly influences on inorganic P (except Al-P) under different fertilization methods in paddy field. Al-P, Fe-P, and Obs-P contents were significantly affected by different fertilization methods in the dry land, but that no significant effects on Ex-P and Ca-P contents. Even in paddy field or dry land condition, Obs-P and Ca-P were as the main inorganic P forms in irrigation silting soils.   Conclusion  Therefore, organic and chemical fertilizers combined with straw incorporation is the most effective method of regulating soil P availability in irrigation silting soils, and it is the significant regulation method in the paddy rice season in the flood and drought rotation system in the Yellow River Irrigation Region in Ningxia.