土壤盐渍化对尿素与磷酸脲氨挥发的影响

氨挥发是肥料氮素损失的重要途径之一，肥料类型、土壤类型、肥料用量以及土壤全盐量均影响氨挥发损失率及挥发特征。本文采用通气法测定了磷酸脲和尿素两种肥料六个施肥量处理分别施入六个不同盐渍化程度（1.7、9.9、16.4、23.2、29.1、37.9 g/kg）的土壤后氨挥发累积状况和动力学特性，以及土壤氨挥发累积量与土壤电导值之间的相关性。结果表明：（1）在土壤总盐介于1.66 -37.9 g/kg的范围内，随着土壤含盐量增加，尿素与磷酸脲处理的氨挥发累积量显著增加；土壤含盐量对氨挥发速率有显著的促进作用。（2）各处理二次线性函数拟合的二项式系数a均为负值，表明：在不同盐渍化条件下肥料的挥发速率是随着时间增长而降低的；一次线性函数和Elovich 方程的斜率a随土壤含盐量增加而增大，表明：土壤盐渍化将加剧土壤的氨挥发速率。（3）土壤氨挥发累积量与电导值拟合结果符合logistic方程（︱R︱分别为0.9732，0.9815，0.965，0.9182，0.9817，0.9971︱R︱>r0.01=0.9172， n=6），氨挥发累积量随土壤电导值呈“S”型增长。

Effects of soil salinization on ammonia volatilization characteristics of urea and urea phosphate

Soil ammonia volatilization (AV) is an important pathway for nitrogen (N) loss from fertilizer. AV is greatly affected by meteorological variable, soil property, N fertilizer, amount of N, and soil water condition. However little information is available on AV with different total contents of soil soluble salts in western China. Saline soil is an important soil resource in arid and semi arid areas. Saline-alkali soil in China covers an area of 3.69 million hectares, and potential salt affected soil occupies an area of 1.7 million hectares. The accumulative amounts and dynamical characteristics of AV from Urea (0.8 and 2.0 g/pot) (UR) and Urea phosphate (1.0, 2.0 and 4.0 g/pot) (UP) in the soils under six different salinity levels (1.7, 9.9, 16.4, 23.2, 29.1, 37.9 g/kg ) were investigated using a method of phosphoric acid and glycerol-sponge venting chamber. The main results are as follows: (1) The amount of AV of UR and UP increased with the increase of total salt content in soil within a limited range (1.7-37.9 g/kg). When the fertilizer treatments were same, the amount of AV in Non-saline soil was significantly smaller than in heavy salinity soil. When the salinity concentrations was 37.9 g/kg, the accumulative amounts of AV from UR2 was 37.6 mg N/kg, while it was 3.3 mg N/kg in soil at salinity level of 1.7 g/kg. The former was 11.4 times higher than the latter. (2) The coefficient a of binomial formula was negative, which suggested the rates of AV from UR and UP decreased with time in different salty soils. The slope of linear function and Elovich Equation increased as the salinity concentrations increased, suggesting that the rates of AV from UR and UP increased with soil salinization. (3) The correlation between the amounts of AV and the soil salinity fitted well the logistic equation(P<0.01). The resulting curve was described as an S curve. These results indicated that AV rates from soil were greatly affected by soil total soluble salt content. Under the same amount of nitrogen application and total content of soil soluble salts, AV losses from Urea phosphate were much lower than that of Urea.