Impact of fruit-tree shade intensity on the growth, yield, and quality of intercropped wheat

Agroforestry is a common traditional practice in China-especially in the southern Xinjiang of Northwest China. However, the productivity of many agroforestry systems has been lower than expected in recent years, highlighting the need for an actionably deep mechanistic understanding of the competition between crops and trees. Here, three different fruit tree/wheat (jujube/wheat, apricot /wheat, and walnut /wheat) intercropping agroforestry systems were chosen to investigate influence of different fruit tree shade intensity on the growth, yield and quality of intercropping wheat. Compared to the monoculture wheat system, the mean daily shade intensity of the jujube-, apricot-, and walnut-based intercropping systems were, respectively, 23.2%, 57.5%, and 80.7% shade. The photosynthetic rate of wheat in the jujube-, apricot-, and walnut-based intercropping systems decreased by, respectively, 11.3%, 31.9%, and 36.2% compared to monoculture wheat, and the mean number of fertile florets per spike decreased by 26.4%, 37.4%, and 49.5%. Moreover, the apricot- and walnut-based intercropping systems deleteriously affected grain yield (constituent components spike number, grains per spike, and thousand grain weight) and decreased the total N, P, and K content of intercropping wheat. Tree shading intensity strongly enhanced the grain protein content, wet gluten content, dough development time, and dough stability time of wheat, but significantly decreased the softening degree. Strong negative linear correlations were observed between tree shade intensity and the number of fertile florets, grain yield related traits (including spike number, grains per spike, and thousand grain weight), nutrient content (N, P and K), and softening degree of wheat. In contrast, Daily shade intensity was positively linearly correlated with grain protein content, wet gluten content, dough development time, and dough stability time. We conclude that jujube-based intercropping systems can be practical in the region, as they do not decrease the yield and quality of intercropping wheat.农林业（Agroforestry）是中国常见的传统农耕模式，尤其在我国西北新疆南部地区广为应用。然而近年来诸多农林业系统的生产力未达预期，凸显了对作物与树木间竞争关系开展切实深入的机制性研究的迫切需求。本研究选取枣麦、杏麦、核桃麦三种果麦间作农林业系统，探究不同果树遮阴强度对间作小麦生长、产量及品质的影响。相较于单作小麦系统，枣麦、杏麦、核桃麦间作系统的日均遮阴率分别为23.2%、57.5%与80.7%。枣麦、杏麦、核桃麦间作系统中小麦的光合速率较单作小麦分别下降11.3%、31.9%与36.2%，每穗可育小花数分别下降26.4%、37.4%与49.5%。此外，杏麦与核桃麦间作系统对小麦籽粒产量（构成要素为穗数、穗粒数及千粒重）产生不利影响，并降低了间作小麦的全氮、全磷与全钾含量。果树遮阴强度显著提升了小麦的籽粒蛋白质含量、湿面筋含量、面团形成时间及面团稳定时间，但显著降低了面团软化度。研究发现，果树遮阴强度与小麦可育小花数、籽粒产量相关性状（包括穗数、穗粒数及千粒重）、养分含量（氮、磷、钾）及面团软化度呈显著负线性相关；与之相反，日均遮阴强度与小麦籽粒蛋白质含量、湿面筋含量、面团形成时间及面团稳定时间呈显著正线性相关。本研究结论认为，枣麦间作系统在该区域具备实践可行性，因其未降低间作小麦的产量与品质。