黄土旱塬区小麦/紫花苜蓿间作群体耗水过程及其优化调控

Application of the forage and grain crops intercropping is one of the efficient ways that help to improve planting structure in grain production areas, which is also in accordance with the grain to forage plan that advocated by the government. Wheat and alfalfa intercropping has the advantages of harvesting grain and forage in the same field, preventing and/or controlling plant diseases, and improving nutrient use efficiency, however, water use and its relationship with key influencing factors in this system are still unclear. How to regulate the water use relations between component crops in the intercropping to enhance water use efficiency and obtain a stable yield advantage, is an urgent question that must be answered before the planting pattern could be applied in dryland farming areas. So field experiments and simulation works will be combined in this project to: analyze wheat and alfalfa canopy and root spatio-temporal dynamics, quantify partitioning and utilization of radiation and water in the system, clarify how above and below ground interspecific interactions influence the water transportation processes, improve the APSIM model based on the experiment, and finally present an optimized managing strategy for the system in the perspective of water use sustainability. The results would be served as one of the bases for promoting the reform of farming system on the loess tableland areas and enhancing the economic and ecological benefits of regional agricultural production.

牧草与粮食作物间作种植是响应国家粮改饲战略、促进农区种植业结构调整的重要措施之一。小麦与紫花苜蓿间作具有粮草并收、防控病害、促进养分利用等诸多优势，但是该模式耗水规律与其关键影响因素之间的关系仍不清晰，能否通过栽培管理优化种间水分利用生态位关系、提高系统水分利用效率、维持高产稳产而不多耗水，是保证该模式在旱作农区大范围推广首先需要回答的问题。本项目将采用大田试验和模型模拟相结合的方法，分析不同施肥和间作模式下小麦/紫花苜蓿间作群体冠层和根系时空演变特征，量化群体光能和水分分配关系及利用规律，揭示地上冠层和地下根系互作协同影响群体水分蒸散的物理机制，改进APSIM模型中计算间作群体水分利用过程的关键模块，最后从水分高效持续利用的角度提出黄土旱塬区小麦/紫花苜蓿间作优化管理模式。研究对于促进黄土旱塬区农业生产结构转型、实现农业生产经济效益和生态效益同步提升具有一定的借鉴意义。

牧草与粮食作物间作种植是促进农业种植业结构调整、提高农业资源利用效率、保障口粮和饲草同时供应的重要措施之一。小麦与紫花苜蓿是黄土高原地区主要的粮食和牧草作物，项目假设小麦和苜蓿带状间作可通过种间水肥互补优化利用防止苜蓿单一种植引起的土壤干燥化、也可减少小麦施肥量。基于此，项目通过4年的大田试验系统研究了小麦-苜蓿带状间作群体的生产效应、种间互作关系及水分利用规律，主要结果包括：1）小麦苜蓿共生期小麦处于竞争优势地位，小麦收获后苜蓿出现补偿性生长，减少氮肥和宽带幅间作模式均具有弱化种间竞争、促进种间互补的作用；2）小麦表现出显著的边行优势，间作小麦有效穗数和千粒重显著提高，单位面积产量比单作小麦提高17.7%-30.0%，小麦苜蓿8:4的宽带幅间作模式4年间的土地当量比最高，在1.12-1.27之间；3）小麦和苜蓿根系均发生侧向生长，小麦主要利用苜蓿条带0-200 cm深处的水分，苜蓿主要利用小麦条带300 cm以下的水分，干旱年份种间水分互补运移量大幅增加；4）建立了苜蓿-粮食作物带状间作群体光能传输利用模型，改进了苜蓿生长作物模型，实现了苜蓿-粮食作物复合种植群体的模拟，建议在黄土高原地区推广8行小麦间作4行苜蓿的带状间作模式，小麦施肥量80 kg ha-1，研究成果对于促进黄土高原旱作农区粮草间作模式推广应用、实现区域农业生产生态效益同步提升具有一定的借鉴意义，应用前景广阔。