基于土壤有机质含量推荐的旱地冬小麦施氮量研究

【目的】 当前国内已有的小麦氮肥用量推荐方法,尤其是基于测土进行的推荐施肥方法,都存在取样量大、测试工作量大和成本较高的问题,难以被农技推广工作者和小农户接纳与应用推广。为此,本文就一种至少2—3年有效的氮肥用量推荐方法进行研究。【方法】 以低有机质含量土壤维持或提高土壤肥力、高有机质土壤降低环境风险为目的,建立基于土壤有机质含量的旱地小麦施氮量推荐方法,施氮量（kg N·hm^-2）=目标产量需氮量（kg N·hm^-2）×施氮系数（N_f）。施氮系数（N_f）由表层土壤有机质含量高低确定。应用这一方法在渭北旱塬冬小麦种植区6县进行了3年田间试验。【结果】 基于有机质推荐氮肥施用量平均为161 kg N·hm^-2,比农户习惯施肥（平均为190 kg N·hm^-2）减少了15.3%;而相应的冬小麦平均籽粒产量为5 817 kg·hm^-2,比农户习惯施肥显著提高了9.0%。此外,与农户习惯施肥相比,基于有机质含量推荐施肥的经济效益增加了1 451元/hm²,提高19.3%,小麦收获期1 m土层的硝态氮残留降低了39 kg·hm^-2,显著降低28.3%。【结论】 基于土壤有机质含量推荐施肥降低了氮肥施用量并提高了冬小麦籽粒产量,增加了经济效益,降低了土壤硝态氮残留量和施肥的环境风险,可在旱地小麦区推广应用。

Research on Nitrogen Fertilizer Application Recommended Method Based on Soil Organic Matter in Dryland Wheat Production

【Objective】 Most of the current existing recommended methods of nitrogen (N) fertilizer application for wheat involved collecting and analyzing a huge quantity of soil samples every year, especially for those based on soil testing, thus these methods were very expensive and difficult to be accepted and applied by the smallholder farmers and junior agricultural technicians. Therefore, it is important to explore an effective N fertilizer recommendation method that does not need testing soil samples each year. 【Method】 A recommended N fertilizer application method that based on the soil organic matter content (SOM) was proposed, the purpose of which was to maintain or improve soil fertility under low SOM condition, and to decrease the environmental risk under high SOM condition in dryland. The N fertilizer application rate was calculated as the N requirement of the target grain yield multiplied by the N fertilizer coefficient (N_f), where N_f was determined by SOM in topsoil. Then a three-year field experiment was conducted to verify this recommended method in six counties of winter wheat planting area in Weibei dryland, with two treatments: FP (Farmers’ practice) and OFP (Optimized fertilization practice based on the method of soil organic matter). 【Result】 The results showed that the average N fertilizer rate of OFP and FP was 161 and 190 kg N·hm^-2, respectively, with a significant decrease of 15.3% by OFP. However, the winter wheat yield in OFP was 5 817 kg·hm^-2and higher (by 9.0%) than that in FP. The net economic return of OFP was 1 451 yuan/hm², with an increase of 19.3% when comparing with FP. In addition, compared with FP, OFP decreased 39 kg·hm^-2nitrate-N residue in 0-1 m soil layers at harvest stage, with a decrease of 28.3%. 【Conclusion】 The recommended N fertilization method based on soil organic matter decreased N fertilizer input increased the wheat grain yield and economic benefits, and reduced the environmental risk in Weibei dryland. Therefore, this method could be taken into account in the management of N fertilizer input by local farmers in this region.