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试验研究了3种酸性土壤和3种碱性土壤施入尿素后,对土壤pH值变化、氨挥发特性、氮素转化及A l元素活性的影响。试验结果表明:土壤酸碱性对尿素水解的影响与尿素浓度有关,在常温25℃下,3种酸性土壤的pH值在短期内都随着加入尿素浓度的增大而急剧上升,而3种碱性土壤的pH值却是随着加入尿素浓度的增加先增加再减少然后又增加,且其变化的幅度较之酸性土壤小;动态试验表明,pH值上升的现象是短期的,6种土壤pH值达到最大值后缓慢下降,2周后3种碱性土壤的pH降到比原来更低的程度。氨挥发强度与土壤pH变化同步;在酸性土壤和碱性土壤中,氨气日挥发量都是先从小到大出现峰值,然后又降低;酸性土壤氨挥发高峰期约在7~9天,碱性土壤的氨挥发高峰期约在第3天左右。各处理NH4+-N含量和NO3--N含量与土壤pH变化趋势相似,在前2~4星期增加到峰值,而后开始下降并保持不变。短期内,交换性A l随着尿素浓度的增大而急剧下降,交换性A l含量与土壤pH变化呈显著负相关,施用尿素短期内能显著降低酸性土壤交换性铝的含量。
The effects of three acidic soils and three alkaline soils on the changes of pH value, ammonia volatilization, nitrogen conversion and Al activity were studied. The results showed that the influence of soil pH on urea hydrolysis was related to the urea concentration. Under normal temperature and 25 ℃, the pH value of three kinds of acid soils increased rapidly with the increase of urea concentration in the short term. However, However, the pH value of alkaline soil increased first, then decreased and then increased with the increase of urea concentration, and the change range was smaller than that of acid soil. Dynamic tests showed that the pH value was increased in a short period, After pH reached a maximum, it slowly decreased. After 2 weeks, the pH of three alkaline soils decreased to a lower level than before. Ammonia volatilization intensity and soil pH changes simultaneously; in acidic soil and alkaline soil, ammonia volatilization amount is the first small to large peak, and then reduce; acid soil ammonia volatilization peak in about 7 to 9 days, alkali The peak of ammonia volatilization in soils is about the third day. The content of NH4 + -N and the content of NO3 - N in all treatments were similar to those of soil pH and increased to the peak in the first two to four weeks, then decreased and remained unchanged. In the short term, the exchangeable A l sharply decreased with the increase of urea concentration, and the exchangeable A l content was negatively correlated with the change of soil pH. The application of urea could significantly reduce the content of exchangeable aluminum in acid soils in a short term.