Table_1_Comparative analysis of farmer practices and high yield experiments: Farmers could get more maize yield from maize-soybean relay intercropping through high density cultivation of maize.docx

Intercropping is a high-yield, resource-efficient planting method. There is a large gap between actual yield and potential yield at farmer’s field. Their actual yield of intercropped maize remains unclear under low solar radiation-area, whether this yield can be improved, and if so, what are the underlying mechanism for increasing yield? In the present study, we collected the field management and yield data of intercropping maize by conducting a survey comprising 300 farmer households in 2016-2017. Subsequently, based on surveyed data, we designed an experiment including a high density planting (Dense cultivation and high N fertilization with plough tillage; DC) and normal farmer practice (Common cultivation; CC) to analyze the yield, canopy structure, light interception, photosynthetic parameters, and photosynthetic productivity. Most farmers preferred rotary tillage with a low planting density and N fertilization. Survey data showed that farmer yield ranged between 4-6 Mg ha-1, with highest yield recorded at 10-12 Mg ha-1, suggesting a possibility for yield improvement by improved cropping practices. Results from high density experiment showed that the two-years average yield for DC was 28.8% higher than the CC. Compared to CC, the lower angle between stem and leaf (LA) and higher leaf area index (LAI) in DC resulted in higher light interception in middle canopy and increased the photosynthetic productivity under DC. Moreover, in upper and lower canopies, the average activity of phosphoenolpyruvate (PEP) carboxylase was 70% higher in DC than CC. Briefly, increase in LAI and high Pn improved both light interception and photosynthetic productivity, thereby mediating an increase in the maize yield. Overall, these results indicated that farmer’s yields on average can be increased by 2.1 Mg ha-1 by increasing planting density and N fertilization, under plough tillage.

间作是一种高产、资源高效化的种植方法。在农民田地中，实际产量与潜在产量之间存在着显著的差距。在低光照辐射条件下，农民间作玉米的实际产量尚不明确，而提高这一产量的可能性以及背后的机制仍需探讨。在本研究中，我们通过于2016-2017年间对300户农民家庭进行问卷调查，收集了间作玉米的田间管理和产量数据。在此基础上，我们设计了一项实验，包括高密度种植（密植与高氮肥施用，耕翻耕作；DC）和常规农民耕作实践（常规耕作；CC），以分析产量、冠层结构、光截获、光合参数和光合生产力。大多数农民倾向于采用旋耕方式，种植密度低，氮肥施用量少。调查数据显示，农民产量介于4-6 Mg ha-1之间，最高记录为10-12 Mg ha-1，表明通过改善耕作实践有可能提高产量。高密度种植实验的结果显示，DC在两年内的平均产量比CC高出28.8%。与CC相比，DC中茎与叶之间的较小角度（LA）和较高的叶面积指数（LAI）导致了中冠层较高的光截获，并增加了DC下的光合生产力。此外，在上层和下层冠层中，DC中磷酸烯醇式丙酮酸羧化酶（PEP）的平均活性比CC高出70%。简而言之，LAI的增加和较高的Pn（光合速率）提高了光截获和光合生产力，从而促进了玉米产量的增加。总体而言，这些结果表明，通过增加种植密度和氮肥施用量，在耕翻耕作条件下，农民的平均产量可以提高2.1 Mg ha-1。