尿素浓度、培养时间和温度对3种土壤尿素水解过程的影响

Effect of urea concentration,incubation time and temperature on urea hydrolysis in 3 different soils

采用较宽幅度尿素浓度、不同温度和不同培养时间对潮土、灰钙土和黄棕壤中尿素水解过程进行了研究。结果表明 ,尿素水解速率深受土壤类型、尿素浓度、温度和培养时间的影响。在 2 5～ 45℃范围内 ,当土壤溶液中尿素浓度大于3 6 6 1mol/L以上时 ,灰钙土的尿素水解速率剧烈下降 ,培养时间越长 ,降幅越大。潮土在尿素浓度大于 5 0 0 8mol/L时也有类似现象。潮土和黄棕壤中存在高亲和性和低亲和性尿素水解反应 ,而灰钙土仅表现出低亲和性反应。土壤脲酶对尿素的亲和系数和尿素水解反应的最大初速度的大小受土壤类型。

The urea hydrolysis characteristics in 3 different soils under a wide range of urea concentration,different incubation time,and different temperature were studied to clarify the hydrolysis behavior of urea applied in band or spot to upland soil.The results showed that the rate of urea hydrolysis in soil at low urea level was enhanced by increased urea concentration and temperature,but decreased by prolonged incubation time.However,high urea concentration could strongly inhibit soil urea hydrolysis.This phenomenon became more striking when both urea concentration and incubation time were increased.The urea hydrolysis rates in sierozems declined dramatically when the urea concentration of soil solution was above 3 661 mol/L and temperature more than 25 ℃.The similar changes were also found in fluvo?aquic soils when the urea concentration was above 5 008 mol/L.There were both high affinity reaction and low affinity reaction of urea hydrolysis in fluvo?aquic soil and yellow?brown earth,while only low one in sierozem.Furthermore,the maximum rate of urea hydrolysis and affinity constant of soil urease were controlled by soil type,the incubation time and temperature.