Department of Geography and Environmental Management, University of Waterloo, Waterloo, Ontario, Canada.
Lower Thames Valley Conservation Authority, Chatham, Ontario, Canada.
J Environ Qual. 2023 Sep-Oct;52(5):1011-1023. doi: 10.1002/jeq2.20502. Epub 2023 Jul 26.
Nutrient and soil loss from agricultural areas impairs surface water quality globally. In the Great Lakes region, increases in the frequency and magnitude of harmful and nuisance algal blooms in freshwater lakes have been linked to elevated phosphorus (P) losses from agricultural fields, some of which are transported via tile drainage. This study examined whether concentrations and loads of P fractions, total suspended sediments (TSS), nitrate (NO ), and ammonium (NH ) in tile drainage in a clay soil differed between a continuous no-till system combining cover crops and surface broadcast fertilizer (no-till cover crop [NTCC]), and a more conventional tillage system with shallow tillage, fertilizer incorporation and limited use of cover crops (conventional conservation-till, CT). Both sites had modest soil fertility levels. Year-round, high-frequency observations of tile drainage flow and chemistry are described over 4 full water years and related to management practices on the associated fields. There were similar water yields in tile drainage between the two systems; however, losses of TSS, particulate P (PP), and NO were consistently greater from the CT site, which received larger quantities of fertilizer. In contrast, dissolved reactive P (DRP) losses were considerably greater from the NTCC site, offsetting the lower PP losses, such that there was little difference in TP losses between sites. Approximately 60% of the DRP losses from the NTCC site over the 4 years were associated with incidental losses following surface application of fertilizer in fall. This study provides insight into trade-offs in controlling losses of different nutrient fractions using different management systems.
农业区的养分和土壤流失会损害全球地表水的质量。在五大湖地区，淡水湖中有害和滋扰性藻类大量繁殖的频率和规模增加与农业用地中磷（P）流失的增加有关，其中一些是通过地下排水渠输送的。本研究考察了在粘土土壤中，采用覆盖作物和地表撒播肥料的连续免耕系统（免耕覆盖作物[NTCC]）与采用浅层耕作、肥料施入和有限使用覆盖作物的更传统耕作系统（常规保护性耕作[CT]）之间，地下排水中 P 组分、总悬浮泥沙（TSS）、硝酸盐（NO ）和铵（NH ）的浓度和负荷是否存在差异。两个地点的土壤肥力水平都适中。本文描述了 4 个完整水文年中全年高频地下排水流动和化学观测，并将其与相关农田管理实践联系起来。两个系统的地下排水产量相似；然而，来自 CT 点的 TSS、颗粒态 P（PP）和 NO 流失量始终更大，因为该点接受了更多的肥料。相比之下，来自 NTCC 点的溶解态反应性 P（DRP）流失量要大得多，抵消了较低的 PP 流失量，因此两个地点的总磷流失量几乎没有差异。在 4 年期间，来自 NTCC 点的 DRP 流失量中约有 60%是在秋季地表施肥后偶然流失的。本研究深入了解了采用不同管理系统控制不同养分组分流失的权衡。
