Because it keeps land in production, conservation programs that focus on in-field habitat manipulations may help farmers better support predators than by building predator habitat around fields. We investigated two in-field habitat manipulations that benefit producers and soil quality: fertilizing with dry-stack cow manure and planting a wheat cover crop. We hypothesized that, compared with inorganic fertilizer and fallow plots, both treatments augment habitat and residue and support more small arthropods that can serve as alternative prey for larger predators. As a result, we expected manure and the cover crop to increase ground-active predators. In turn, these predators could provide biological control of pests. Each year in a 3-yr field experiment, we applied manure and in 2 yr planted a wheat cover crop. We found that both planting a cover crop and applying dry-stack manure increased the plant cover in May. In the last year, this translated to greater soil mite (Acari) density. At the end of the experiment, however, neither manure nor the wheat cover crop had increased residue on the soil surface. As a result, our treatments had inconsistent effects on predator activity-density, especially for carabids and spiders. We observed strong edge effects from neighboring grass alleys on carabid activity-density. Regardless of treatment, we observed high predation of sentinel prey. We conclude that even without cover crops or organic fertilizer, the stability of no-till maize and increased weeds in fallow treatments generate sufficient habitat complexity and alternative prey to support robust predator communities.

中文翻译：

---

免耕玉米中干堆牛粪和小麦覆盖作物对地面捕食者活动密度和捕食率的支持较弱

因为它使土地保持生产，专注于田间栖息地操纵的保护计划可能会帮助农民更好地支持捕食者，而不是在田地周围建立捕食者栖息地。我们调查了两种有益于生产者和土壤质量的田间栖息地操作：用干堆牛粪施肥和种植小麦覆盖作物。我们假设，与无机肥料和休耕地相比，这两种处理方法都增加了栖息地和残留物，并支持了更多的小型节肢动物，这些节肢动物可以作为大型捕食者的替代猎物。因此，我们预计粪便和覆盖作物会增加地面活动的捕食者。反过来，这些捕食者可以提供对害虫的生物控制。每年在为期 3 年的田间试验中，我们施用肥料并在 2 年内种植小麦覆盖作物。我们发现种植覆盖作物和施用干堆肥都增加了 5 月的植物覆盖率。在去年，这转化为更大的土壤螨（螨）密度。然而，在实验结束时，无论是粪肥还是小麦覆盖作物都没有增加土壤表面的残留物。结果，我们的处理对捕食者活动密度的影响不一致，尤其是对甲壳类动物和蜘蛛。我们观察到邻近草巷对鳐鱼活动密度的强烈边缘效应。无论治疗如何，我们都观察到哨兵猎物的高度捕食。我们得出的结论是，即使没有覆盖作物或有机肥料，免耕玉米的稳定性和休耕处理中杂草的增加也会产生足够的栖息地复杂性和替代猎物，以支持强大的捕食者群落。