水温因素与夏玉米生长季节土壤矿质氮动态的关系

农田土壤的矿质氮残留和淋溶已成为大气和水体氮污染的重要来源。本文通过位于黄土高原南部的田间试验,研究了气温、土壤温度和水分、灌溉和降水等环境条件与夏玉米生长季节土壤残留矿质氮素动态变化的关系。结果表明:①0～200cm土层铵态氮残留量与耕层土壤温度的动态变化趋势一致,但土壤硝态氮残留量与土壤温度变化趋势相反。②大气温度对土壤矿质氮数量的影响趋势和土壤温度的基本相同。③在夏玉米生长季节0～200 cm土层土壤含水量平均值呈波动增加趋势,土壤铵态氮和硝态氮残留量随土壤水分的增减而增减,矿质氮素增减变化与土壤含水量相比有滞后现象。④夏玉米生长季节降水和灌水量达到720.5 mm,大量水分使得土壤硝态氮随着夏玉米生长期的后移而有明显的向下淋移趋势。玉米收获时,土壤硝态氮已被淋失到200 cm以下土层,难以再被下季作物利用。

Relations Between Water and Temperature Factors and Dynamics of Soil Mineral Nitrogen During Summer Maize Growing Season

Mineral N residual in dryland soil has been proved to be the main source for regional air and water pollution.In this paper,field experiments were carried out to study the relations between environmental conditions of air temperature,soil temperature and moisture content,irrigation and precipitation etc.to the dynamic changes of soil residual mineral nitrogen during summer maize growing seasons in the southern area of the Loess Plateau.The results indicated that: ①Residual amount of soil ammonium nitrogen in 0-200 cm soil was observed to be changed positively with the dynamic change of topsoil temperature,but the residual amount of soil nitrate nitrogen in 0-200 cm soil layer was changed negatively with the soil temperature.②Effects of air temperature on amount of soil residual mineral nitrogen showed basically same trend with soil temperature.③Average soil moisture contents in 0-200 cm soil had a undulating increase trend during summer maize growing season.The residual amount of soil ammonium and nitrate nitrogen increased or decreased with the soil moisture content,but change of mineral nitrogen was found to be lagged compared to soil moisture content.④Total amount of irrigation and precipitation was 720.5 mm during of the summer maize growing season in this experiment.An obvious leaching of nitrate nitrogen in soil profile occurred due to so big amount of water during the summer maize growing season.At harvest time of summer maize,most nitrate nitrogen had already been leached down bellow 200 cm soil,and it was difficult to be reused by following crops.Nitrate continuously moving down to the deep soil layers will form a potential threat to the underground water.