南方丘陵地区农田氮素渗漏特征研究

农田氮肥的淋失是氮素损失的重要途径之一.在南方丘陵地区选择4种土地利用类型中6个农田地块进行为期1年的氮素渗漏试验,结果表明:(1)不同的土地利用类型的硝氮浓度变化趋势为春季种植季节后逐渐升高,在7-8月份达到最高,然后呈逐渐下降的趋势,呈低-高-低的变化趋势.氨氮浓度与硝氮浓度的消长规律相似,但变化规律不如硝氮浓度明显,时有起伏.(2)土壤中氮素渗漏的基本形态是硝氮,农田氮素的渗漏主要发生在4-8月份.(3)施肥对氮素渗漏量的影响非常显著.施肥量和施肥种类的不同,导致不同土地利用类型浅层地下水的硝氮和氨氮浓度差异较大.施肥量越大,其渗漏量也越大.主要施用碳氨品种化肥的土地利用,其渗漏水中硝氮浓度相对较高,氨氮浓度比较低,而施粗制有机肥的土地利用氨氮浓度表现较高.(4)对地下水位较高的土地利用农田渗漏水中氨氮浓度相对较高.适当的化肥施用量可以减少氮素淋失.

Research on Nitrogen Leaching Characteristic in Southeast Hill-land Area

Nitrogen leaching caused by chemical fertilizer is a main source of nitrogen pollution of ground water.Field leaching experiments were conducted in southeast hill-land watershed whole year.Six boreholes were drilled and monitoring pipes were installed under forth land uses,such as paddy,uncultivated land ,bananas,and vegetables,for continuously monitoring of nitrate and ammonium leaching.In general,(1) a parabola-like pattern of leaching nitrate concentration was found under different land uses.Nitrate concentration increase after spring,get the peak value in July or August,and then become decreasing.Changing trends of ammonium concentration of various landuse is similar to changing pattern of leaching nitrate concentration.But changing rule of ammonium concentration is not better obvious than that of nitrate concentration.(2)Basic form of nitrogen leaching was nitrate concentration,main leaching periods wass from April to August.(3) Chemical fertilizer influence on nitrogen leaching was very obvious.There was diffirence in leaching nitrate concentration and ammonium concentration of various landuse,because of different inputs chemical fertilizer quantity and sort.In general,Inputs chemical were more,leacing nitrogen were bigger.Leaching nitrate concentration of ammonium bicarbonate inputs was much more high relativityly with fertilizer and manure,but ammonium concentration was much more low.But manure inputs can cause much more higher ammonium concentration.(4) Concentration of ammonium in ground water was higher than nitrate under hydraulic conditions of high ground water table.However,there was adverse resultsunder hydraulic conditions of low ground water table.Moderate fertilizer application quantities could reduce notrogen loss.