不同因素交互作用对棕壤硝态氮累积及pH值的影响

本文采用室内恒温好气培养法，研究了温度（10℃和30℃）、水分（田间持水量的70%和100%）及尿素态氮用量（N 0、450、600、750）mg/kg 的交互作用对硝态氮累积和土壤酸化的影响。结果表明， 10℃下硝化作用进行缓慢，最大硝化率(K max)与施氮量呈极显著负相关（r=-0935**），达到最大硝化率的时间(t0)与尿素态氮用量呈极显著正相关（r=0876**）。30 ℃下的硝化率随尿素态氮用量的增加而增加。低温环境延长了t0。10 ℃（70%和100%含水量）下，N 750 mg/kg 处理的t0分别相当于30 ℃下该处理的1.9 和 2.5 倍。所有处理土壤的硝态氮累积量均随培养热量的增加呈指数增长趋势， 且70%含水量下的累积量高于100% 含水量下的累积量， N 600 和 750 mg/kg 处理的累积量显著高于其他处理。培养结束后，30 ℃所有处理的pH值均显著低于初始土壤，其中N 600 和 750 mg/kg 处理的pH5.1， 酸化明显。通径分析结果表明， 尿素施用量和培养天数是影响硝化率进而影响pH值的重要因素，其次是培养温度和含水量。

Effects of interaction of different factors on nitrate nitrogen accumulation and pH of brown soil

A constant temperature incubation experiment was conducted to evaluate effects of temperature (10℃ and 30℃), soil moisture content (70% and 100%), urea nitrogen rate (0, 450, 600 and 750 mg/kg) and their interaction on nitrate nitrogen accumulation and soil acidification. The results show that nitrification is slowly under 10℃, and significantly negative and positive correlations are found between Kmax (maximal nitrification rate) and urea nitrogen rate (r=-0.935**), t0 (time of maximal nitrification rate) and urea nitrogen rate (r=0.876**), respectively. The nitrification rate is increased as the increase of the urea nitrogen rate under 30℃. Days of t0 are prolonged under the low temperature. The t0 values of the urea nitrogen rate of 750 mg/kg under 10℃ are 1.9 and 2.5 times larger than those under 30℃ with soil moisture of 70% and 100%, respectively. An exponent increasing trend is found between the nitrate nitrogen accumulation and the degree days after urea application in all treatments, and the accumulation amount is higher with soil moisture content of 70% than that of 100%. Significant accumulations are found under the urea nitrogen rates of 600 and 750 mg/kg. Soil pH values of all treatments are lower than that of the initial soil under 30℃, and pH values of urea nitrogen rates of 600 and 750 mg/kg are less than 5.1, which shows a significant acidification. Results of the path analysis show that amount of urea nitrogen and incubation day are two key factors that affected nitrification rate and then affected soil pH, and the other factors are incubation temperature and soil moisture content.