非饱和带全剖面尿素态氮迁移转化规律分析

尿素是农田常用氮肥,本文通过实验室土柱试验,利用HYDRUS-1D建立非饱和带尿素态氮迁移转化模型,并对大沽河地下水源地夏玉米生长季节内水氮运移过程进行模拟,分析灌溉农业条件下非饱和带全剖面中氮迁移转化和深层淋溶规律。结果表明:(1)常规施肥条件下,尿素态氮水解达97.09%,仅有0.01%能够淋溶至地下水;(2)硝态氮更易淋溶至地下水,硝态氮淋失量与灌溉量和施肥量呈正相关,与灌溉强度呈负相关,不同施肥方式下淋失量表现为深施>灌施>表施;(3)根系吸氮量与灌溉量和施肥量呈正相关,与灌溉强度呈负相关,不同施肥方式下吸氮量表现为灌施>深施>表施,不同管理策略下玉米氮素利用率为20%~50%;(4)常规条件下土壤储氮量>玉米氮素利用率>氮淋溶量>气态氮损失。本研究对量化氮迁移转化过程、定量评价氮损失、预测地下水氮污染具有重要意义。

Analysis of Urea Nitrogen Migration and Transformation Law in Full Profile of Unsaturated Zone

Farmland nitrogen leaching is the main cause of groundwater pollution.It is very important to establish accurate numerical model of unsaturated zone to simulate and predict soil nitrogen migration and transformation process.Urea is a commonly used nitrogen fertilizer farmland,through laboratory soil column experiments,HYDRUS-1D was used to establish a model of urea nitrogen migration and transformation in unsaturated zone,and to simulate the water and nitrogen migration process during summer corn growing season in the groundwater source of Dagu River.At the same time,the law of nitrogen migration and transformation and deep leaching in the full profile of the unsaturated zone under the condition of irrigated agriculture was analyzed.The results show that(1)Under the condition of conventional fertilization,urea nitrogen is not easy to be leached to groundwater,hydrolysis is up to 97.09%,only 0.01%can be leached to groundwater;(2)Nitrate nitrogen is more easily leached to groundwater,and the influence of irrigation mode on leaching is significantly greater than that of fertilization mode.The leaching loss of nitrate nitrogen is positively correlated with irrigation amount and fertilizer amount,but negatively correlated with irrigation intensity.Under different fertilization modes,the leaching loss is manifested as Deep applying>Fertilizer solution>Surface fertilization;(3)The nitrogen uptake of the root system was positively correlated with the amount of irrigation and fertilizer applied,but negatively correlated with the intensity of irrigation.The nitrogen uptake under different fertilization methods was shown as Fertilizer solution>Deep applying>Surface fertilization,and the nitrogen utilization rate of maize under different management strategies was 20%~50%;(4)Soil nitrogen storage capacity>corn nitrogen utilization ratio>nitrogen leaching capacity>gaseous nitrogen loss under conventional conditions,nitrate nitrogen leaching is the main way of nitrogen loss.This study is of great significance for quantifying the process of nitrogen migration and transformation,quantitatively evaluating nitrogen loss and predicting groundwater nitrogen pollution.