Han Kun, Kleinman Peter J A, Saporito Lou S, Church Clinton, McGrath Joshua M, Reiter Mark S, Tingle Shawn C, Allen Arthur L, Wang L Q, Bryant Ray B
J Environ Qual. 2015 Mar;44(2):560-71. doi: 10.2134/jeq2014.08.0326.
Leaching of nutrients through agricultural soils is a priority water quality concern on the Atlantic Coastal Plain. This study evaluated the effect of tillage and urea application on leaching of phosphorus (P) and nitrogen (N) from soils of the Delmarva Peninsula that had previously been under no-till management. Intact soil columns (30 cm wide × 50 cm deep) were irrigated for 6 wk to establish a baseline of leaching response. After 2 wk of drying, a subset of soil columns was subjected to simulated tillage (0-20 cm) in an attempt to curtail leaching of surface nutrients, especially P. Urea (145 kg N ha) was then broadcast on all soils (tilled and untilled), and the columns were irrigated for another 8 wk. Comparison of leachate recoveries representing rapid and slow flows confirmed the potential to manipulate flow fractions with tillage, albeit with mixed results across soils. Leachate trends in the finer-textured soil suggest that tillage impeded macropore flow and forced greater matrix flow. Despite significant vertical stratification of soil P that suggested tillage could prevent leaching of P via macropores from the surface to the subsoil, tillage had no significant impact on P leaching losses. Relatively high levels of soil P below 20 cm may have served as the source of P enrichment in leachate waters. However, tillage did lower losses of applied urea in leachate from two of the three soils, partially confirming the study's premise that tillage would destroy macropore pathways transmitting surface constituents to the subsoil.
养分通过农业土壤的淋溶是大西洋沿岸平原水质的一个优先关注问题。本研究评估了耕作和施用尿素对之前一直采用免耕管理的德尔马瓦半岛土壤中磷（P）和氮（N）淋溶的影响。完整的土柱（宽30厘米×深50厘米）灌溉6周以建立淋溶响应基线。干燥2周后，对一部分土柱进行模拟耕作（0 - 20厘米），试图减少表层养分尤其是磷的淋溶。然后在所有土壤（耕作和未耕作的）上撒施尿素（145千克氮/公顷），并将土柱再灌溉8周。代表快速和慢速水流的渗滤液回收率比较证实了通过耕作控制水流部分的潜力，尽管不同土壤的结果不一。质地较细土壤中的渗滤液趋势表明，耕作阻碍了大孔隙流并迫使更多基质流。尽管土壤磷有显著的垂直分层，这表明耕作可以防止磷通过大孔隙从表层淋溶到下层土壤，但耕作对磷的淋溶损失没有显著影响。20厘米以下相对较高水平的土壤磷可能是渗滤液中磷富集的来源。然而，耕作确实降低了三种土壤中两种土壤渗滤液中施用尿素的损失，部分证实了该研究的前提，即耕作会破坏将表层成分传输到下层土壤的大孔隙通道。
