Assessing a century of maize and soybean polyculture for silage production: Data

This dataset and accompanying supplemental materials are companion pieces to the journal article “Assessing a century of maize and soybean polyculture for silage production” published in Agronomy Journal in 2022 by Burton & Kemanian. Maize (Zea mays L.) silage is an important source of feed for ruminant animals. However, maize monocultures are exposed to both abiotic and biotic stresses that can reduce yield and contribute to environmental degradation. Over the past century, maize + soy (Glycine max (L.) Merr.) polycultures gained traction because polycultures diversify silage cropping systems and can increase the nutritional quality of silage compared to maize monocultures. However, it remains unclear under which conditions these polycultures provide biomass yields like those of maize monocultures. We compiled paired data from 30 papers (529 records) that reported maize and maize + soy yields for silage. Using random forest, we created two models to investigate the factors determining yield and the yield differential with respect to maize monocultures. We found that the most important variables in determining the polyculture yield were the maize proportion in the mixture and year, where year represents mostly technology trends. Precipitation and temperature remain pivotal, with yields stabilizing when yearly precipitation exceeds 100 cm and average temperature exceeds 15 °C. Maize + soy polycultures may produce similarly to maize monocultures if the maize density is at least 5.3 plants m-2. This signals that while biomass production in polycultures is maize-driven, maize stands can be supplemented with soy, or with other suitable companion crops, without sacrificing yield and perhaps capturing additional production and ecosystem benefits. Research on polycultures for silage production should focus on economical ways of planting mixtures and on suitable maize companions for each region.

本数据集与配套补充材料，是2022年发表于《Agronomy Journal》的论文《青贮生产中玉米与大豆混播模式的百年评估》的配套成果，作者为Burton与Kemanian。玉米（Zea mays L.）青贮饲料是反刍动物的重要饲料来源。然而，单作玉米会同时面临非生物与生物胁迫，此类胁迫不仅会降低产量，还会加剧环境退化。近一个世纪以来，玉米-大豆（Glycine max (L.) Merr.）混播模式逐渐得到推广，原因在于混播能够丰富青贮种植系统的多样性，且相较于单作玉米，可提升青贮饲料的营养品质。但目前仍未明确，在何种条件下该混播模式能够达到与单作玉米相当的生物量产量。我们从30篇相关研究论文中整理得到成对数据（共计529条记录），这些论文均报道了单作玉米与玉米-大豆混播的青贮产量。我们采用随机森林（Random Forest）算法构建了两个模型，用以探究影响产量的因素，以及混播模式与单作玉米的产量差异。研究结果显示，决定混播产量的核心变量为混播组合中的玉米占比与种植年份，其中年份主要代表技术发展趋势。降水与气温同样发挥关键作用：当年降水量超过100厘米、平均气温超过15℃时，产量会趋于稳定。若玉米种植密度至少达到5.3株/平方米，玉米-大豆混播模式的产量可与单作玉米相当。这表明，尽管混播模式的生物量生产主要由玉米主导，但通过搭配大豆或其他适宜伴生作物，可在不牺牲产量的前提下，额外获取更多生产收益与生态系统效益。未来针对青贮生产用混播种植模式的研究，应聚焦于实现混播种植的经济可行方案，以及适配各区域的玉米伴生作物筛选。