Randall G W
University of Minnesota, Waseca 56093.
Am J Ind Med. 1990;18(4):457-60. doi: 10.1002/ajim.4700180417.
Conservation tillage systems facilitate the infiltration of greater amounts of precipitation into the soil profile by reducing surface runoff. Concern has developed among some scientists because higher infiltration and percolation rates are often linked to potentially higher leaching losses of agricultural chemicals. Soil samples were taken in 1 foot increments to a depth of 5 feet to ascertain the accumulation and distribution of nitrate-nitrogen (NO3-N) in the soil profile as influenced by tillage. Two long-term tillage studies on fine-textured, clay loam soils were sampled in July and November 1977 following 2 years of limited rainfall. Nitrate-N accumulation in the 0 to 3 foot profile in late July was reduced by 75% (no tillage) to 38% (chisel plow) compared with the conventional moldboard tillage system in this 8-year-old study. Accumulation in the 0 to 5 foot profile after harvest was 751, 546, 345, and 198 lb NO3-N/A for the moldboard plow, chisel-plow, disk-, and no-tillage systems, respectively. Another 3 year study showed accumulations of 625, 619, 468, and 391 pounds NO3-N/A after harvest with the moldboard plow, ridge-plant, chisel-plow, and no-tillage systems, respectively. These data indicate that tillage can have substantial effects on the accumulation of NO3 in soils and that additional research is needed to determine the mechanisms responsible for these differences.
保护性耕作系统通过减少地表径流，促进更多降水渗入土壤剖面。一些科学家对此表示担忧，因为较高的入渗和渗透速率往往与农用化学品潜在的更高淋失损失相关。以1英尺的增量采集土壤样本，深度达5英尺，以确定耕作对土壤剖面中硝态氮（NO3-N）积累和分布的影响。1977年7月和11月，在两年降雨有限之后，对质地细密的粘壤土进行了两项长期耕作研究采样。在这项为期8年的研究中，与传统铧式犁耕作系统相比，7月下旬0至3英尺剖面中的硝态氮积累量减少了75%（免耕）至38%（凿式犁）。收获后，铧式犁、凿式犁、圆盘耙和免耕系统在0至5英尺剖面中的积累量分别为751、546、345和198磅NO3-N/英亩。另一项为期3年的研究表明，收获后铧式犁、垄作、凿式犁和免耕系统的硝态氮积累量分别为625、619、468和391磅NO3-N/英亩。这些数据表明，耕作对土壤中NO3的积累有重大影响，需要进一步研究以确定造成这些差异的机制。
