Dep. of Agronomy, Kansas State Univ., 2004 Throckmorton Plant Sciences Center, 1712 Claflin Rd., Manhattan, KS, 66506, USA.
J Environ Qual. 2020 Jan;49(1):97-105. doi: 10.1002/jeq2.20019. Epub 2020 Jan 20.
Cover crops are often recommended as a best management practice to reduce erosion, weed pressure, and nutrient loss. However, cover crops may be sources of phosphorus (P) to runoff water after termination. Two greenhouse trials were conducted to determine the effects of cover crop species, termination method, and time after termination on water-extractable P (WEP) release from crop biomass. Treatments were structured in a 3 × 3 × 3 factorial and arranged in a randomized complete block design with six replicates. Treatments included three cover crop species (triticale [× Triticosecale; Triticum × Secale 'Trical'], rapeseed [Brassica napus L. 'Winfred'], and crimson clover [Trifolium incarnatum L.]); three termination methods (clipping, freezing, and herbicide); and three WEP extraction times (1, 7, and 14 d after termination). Rapeseed consistently resulted in the least WEP when exposed to the same method of termination and at the same extraction time as the other species. For both trials, terminating crop tissue via freezing increased concentrations of WEP compared with other termination methods. The WEP release from cover crop tissue increased as the time after extraction increased, but the effect was greater for herbicide- and freeze-terminated cover crops and less for clipping-terminated cover crops. Future studies on WEP release from cover crops should pay close attention to the effects of extraction timing. Producers may be able to reduce P loss from cover crop tissue by selecting cover crop species with low WEP and minimizing the amount of biomass exposed to freezing conditions.
覆盖作物通常被推荐为一种最佳管理措施，以减少侵蚀、杂草压力和养分流失。然而，在终止后，覆盖作物可能成为径流水中磷（P）的来源。进行了两项温室试验，以确定覆盖作物种类、终止方法和终止后时间对作物生物量中可水提取磷（WEP）释放的影响。处理采用 3×3×3 析因设计，并以随机完全区组设计排列，设 6 个重复。处理包括三种覆盖作物（黑小麦[× Triticosecale；Triticum × Secale 'Trical']、油菜[Brassica napus L. 'Winfred']和红三叶草[Trifolium incarnatum L.]）；三种终止方法（刈割、冷冻和除草剂）；和三种 WEP 提取时间（终止后 1、7 和 14 天）。在相同的终止方法和相同的提取时间下，油菜的 WEP 浓度始终最低。对于两次试验，与其他终止方法相比，通过冷冻终止作物组织会增加 WEP 的浓度。随着提取后时间的增加，覆盖作物组织中 WEP 的释放量增加，但对除草剂和冷冻终止的覆盖作物的影响更大，对刈割终止的覆盖作物的影响较小。未来关于覆盖作物 WEP 释放的研究应密切关注提取时间的影响。通过选择 WEP 浓度低的覆盖作物品种，并尽量减少暴露于冷冻条件下的生物量，生产者可能能够减少覆盖作物组织中 P 的损失。
