Forage maize is the predominant crop in the intensive dairy farming regions of Europe. This crop, however, is associated with considerable nitrate leaching and decreasing soil organic matter concentrations. Catch crops installed after maize harvest can usually only be sown late in the growing season in North-West Europe to tackle these problems efficiently. Intercropping maize with grass species such as tall fescue has the potential to result in a timely developed grass sward before the winter, capable of assimilating important quantities of carbon and soil residual nitrogen and to buildup soil organic matter. Yet, the intercropped grass might compete with the maize for water and nutrients. Here, we report, for the first time, the effect of (i) herbicide combinations, (ii) tall fescue sowing density and method, (iii) tall fescue morphotype, and (iv) the maize maturity group on the functioning of forage maize intercropped with tall fescue. We assessed maize and intercropped tall fescue yields and studied the N uptake and the effect on soil residual nitrate of the intercropped grass. We found that every kg dry matter ha⁻¹ of tall fescue aboveground dry matter, present at the end of the autumn, came at a cost of 1.4 kg dry matter ha⁻¹ of maize dry matter yield. Herbicide treatments can regulate grass-maize competition, whereas lower sowing densities of the intercropped grass or different sowing methods of the intercropped grass had no effects. Despite the superior winter growth of the Mediterranean tall fescue morphotype compared to the continental tall fescue, the reduction in soil residual nitrate was similar for both morphotypes. We demonstrate that tall fescue intercropped in maize can be an alternative to cover crops installed after the harvest of maize, to reduce nitrate leaching, and to compensate for the soil organic matter losses associated with forage maize production.

饲料玉米是欧洲集约化奶牛养殖区的主要作物。然而，这种作物与大量的硝酸盐浸出和土壤有机质浓度降低有关。玉米收获后种植的作物通常只能在西北欧的生长季节后期播种，以有效解决这些问题。将玉米与高羊茅等草种间作有可能在冬季之前及时形成草丛，能够吸收大量的碳和土壤残留氮并积累土壤有机质。然而，间作的草可能会与玉米竞争水和养分。在这里，我们首次报告了（i）除草剂组合，（ii）高羊茅播种密度和方法，（iii）高羊茅形态型，(iv) 玉米成熟组对高羊茅间作饲料玉米的功能。我们评估了玉米和间作高羊茅的产量，并研究了氮吸收和间作草对土壤残留硝酸盐的影响。我们发现每公斤干物质公顷^-1高羊茅地上干物质，出现在秋季末，损失了 1.4 kg 干物质 ha ^-1玉米干物质产量。除草剂处理可以调节草玉米的竞争，而较低的间作草的播种密度或不同的间作草的播种方法没有影响。尽管与大陆高羊茅相比，地中海高羊茅形态类型的冬季生长优越，但两种形态类型的土壤残留硝酸盐减少量相似。我们证明，在玉米中间作高羊茅可以替代玉米收获后安装的覆盖作物，以减少硝酸盐浸出，并补偿与饲料玉米生产相关的土壤有机质损失。