Oquist K A, Strock J S, Mulla D J
Mississippi Watershed Management Organization, 2520 Larpenteur Ave. W., Lauderdale, MN 55113, USA.
J Environ Qual. 2007 Jun 27;36(4):1194-204. doi: 10.2134/jeq2006.0274. Print 2007 Jul-Aug.
Agricultural runoff contributes nutrients to nonpoint-source pollution of surface waters. This study was conducted to investigate the potential use of alternative farming practices to improve water quality. The study examined the effects of both alternative and conventional farming practices on subsurface drainage and nitrogen and phosphorus loss through subsurface drainage from glacial till soils (i.e., Calciaquolls, Endoaquolls, Eutrudepts, Hapludolls) in southwest Minnesota. Alternative farming practices included organic management practices, species biodiversity, and/or practices that include reduced inputs of synthetic fertilizer and pesticides. Conventional farming practices include corn-soybean (Zea mays L.-Glycine max L., respectively) rotations and their associated recommended fertilizer rates as well as pesticide usage. Precipitation was highly variable during the 3-yr study period including a below-average year (2003), an average year (2002), and an above-average year (2004). Results indicate that alternative farming practices reduced subsurface drainage discharge by 41% compared with conventional practices. Flow-weighted mean nitrate-nitrogen (nitrate N) concentrations during tile flow were 8.2 and 17.2 mg L(-1) under alternative and conventional farming practices, respectively. Alternative farming practices reduced nitrate N losses by between 59 and 62% in 2002 and 2004 compared with conventional practices. Ammonium-nitrogen (ammonium N), orthophosphorus, and total phosphorus losses in subsurface drainage were very low and did not pose a substantial risk of pollution. Results suggest that alternative farming practices have the potential to reduce agricultural impacts on water quality.
农业径流会为地表水的非点源污染贡献养分。本研究旨在调查采用替代耕作方式改善水质的潜在用途。该研究考察了替代耕作方式和传统耕作方式对明尼苏达州西南部冰川冰碛土（即钙质潮湿淋溶土、内生潮湿淋溶土、饱和湿润雏形土、薄层淋溶土）地下排水以及通过地下排水造成的氮和磷流失的影响。替代耕作方式包括有机管理措施、物种生物多样性和/或减少合成肥料和农药投入的措施。传统耕作方式包括玉米 - 大豆（分别为玉米（Zea mays L.）和大豆（Glycine max L.））轮作及其相关的推荐施肥量以及农药使用情况。在为期3年的研究期间，降水量变化很大，包括低于平均水平的一年（2003年）、平均水平的一年（2002年）和高于平均水平的一年（2004年）。结果表明，与传统耕作方式相比，替代耕作方式使地下排水流量减少了41%。在替代耕作方式和传统耕作方式下，瓦管排水期间流量加权平均硝酸盐氮（硝酸盐N）浓度分别为8.2和17.2 mg L⁻¹。与传统耕作方式相比，替代耕作方式在2002年和2004年使硝酸盐N流失减少了59%至62%。地下排水中的铵态氮（铵N）、正磷酸盐和总磷流失量非常低，不存在重大污染风险。结果表明，替代耕作方式有可能减少农业对水质的影响。
