黄淮海平原集约化种植条件下的土壤剖面硝态氮变化

通过田间试验研究玉米-冬小麦轮作系统下,两种不同水平的N肥施用量对NO3--N在黄淮海平原土壤剖面的分布及其动态变化规律的影响,并评估其对环境的潜在污染能力.土壤NO3--N监测为每间隔20 cm至剖面深180 cm.结果表示:作物收获后土壤剖面0～180 cm的残留NO3--N含量为107～443 kg/hm2,年际间和不同作物间的变异性较大.土壤剖面NO3--N含量随着施肥量的增加有增加的趋势,但差异不显著.当前当地农民常规施肥量处理和为常规施肥量2倍处理在试验期间出现的土壤剖面NO3--N含量峰值均在2003年的玉米生长季节,分别为688 kg/hm2和881 kg/hm2,但该玉米生长季节出现的大雨导致占0～180 cm土层50%左右的NO3--N积累在100～180 cm土层深处,该深度的NO3--N比较容易通过淋洗迁移出作物-土壤系统,也有可能是潜在的作物N素来源.由于类似大雨在当地出现的频率比较高,因此,即使在当前当地农民的传统耕作管理措施下,土壤NO3--N可能存在对环境的污染威胁,但程度如何,尚需进一步研究.

Variation of Soil NO3--N in Content and Its Distribution in Soil Profile under Intensive Agriculture in the North China Plain

A field experiment was conducted in the North China Plain to investigate effect of N application rate on soil NO₃^--N and its distribution in the soil profile under a maize-winter-wheat cropping system.The potential hazard of soil NO₃^--N to the environment was also evaluated.Soil NO₃^--N contents were measured of soil layers,20 cm each,of a 180-cm deep soil profile.After the crops were harvested soil NO₃^--N residues in the profile varied greatly from year to year and from crop to crop in the field experiment with values ranging from 107 to 443 kg/hm².A general trend of soil NO₃^--N content increasing with N application rate was observed,while significant difference was hardly observed.During the experiment,a peak soil NO₃^--N content of 688 and 881 kg/hm² for present local farmers'' traditional N rate and 2 times the traditional N rate, respectively,was observed in the growth period of maize in 2003.It is generally considered that the soil NO₃^--N within the layer of 100~180 cm could easily transport by leaching to the environment that beyond the bottom of the plant-soil system or be regarded as potential N source for subsequent crop growth.About 50% of the soil NO₃^--N content at layers of 0~180 cm was accumulated in the deeper layers of 100~180 cm during the growth period of maize in 2003,mainly caused by the heavy rainfall occurred concurrently.It was reported that such kind of heavy rainfall occurred with high frequency.Therefore,potential contamination with NO₃^--N might occur even with local farmers'' traditional management strategy. Further research is required to investigate the contamination degree.