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长期以来反硝化作用被视为水稻田肥科氮损失的主要机制之一,但在田间直接测定反硝化损失还只是新近的事。本文小结了直接和间接测定稻田氮素反硝化损失的结果并评价了各种测试方法的现状。最近在菲律宾、泰国和印度尼西亚12个田间试验中采用~(15)N标记尿素直接测定了(N_2+N_2O)-~(15)N的回收量,其回收量仅占施氮量的0.1%～2.2%,而气态氮总损失(采用~(15)N平衡技术测定)高达10～56%。看来,试验地区反硝化损失主要受硝态氮供应量的限制,而不大受有效碳的影响。在不存在径流和淋溶损失的条件下,从~(15)N标记的硝态氨中逸出的(N_2+N_2O)-~(15)N量远比未回收的~(15)N低。这部分可代表总的反硝化损失。这表明,直接测得的(N发_2+N_2O)-~(15)N量低估了尿素的反硝化损失。而用差减法~(15)N总损失减去氨挥发)所估测反硝化损失的变异很大。研究还表明,在水稻种植期间和两季水稻之间土壤的干湿交替都会导致硝化-反硝化损失。今后仍有必要进一步测定粘闭和淹水稻田土壤的反硝化损失量。
Denitrification has long been regarded as one of the major mechanisms for nitrogen loss in paddy fields, but direct determination of the loss of denitrification in the field is only new. This paper summarizes the results of direct and indirect determination of nitrogen denitrification losses in rice fields and evaluates the current status of various testing methods. Recently, the recoveries of (N 2 + N 2 O) - (15) N were measured by using (15) N labeled urea in 12 field trials in the Philippines, Thailand and Indonesia, 2.2%, while the total loss of gaseous nitrogen (measured by ~ (15) N equilibrium technique) is as high as 10-56%. It appears that the loss of denitrification in the experimental area is mainly limited by the supply of nitrate nitrogen, rather than the effect of available carbon. In the absence of runoff and leaching losses, the amount of (N 2 + N 2 O) - (15) N released from ~ (15) N nitrate nitrate was much lower than that of uncollected (15) N . This section can represent the total loss of denitrification. This indicates that the direct measurement of (N 2 O 2 + N 2 O) ~ (15) N underestimates the denitrification losses of urea. However, the variation of denitrification loss is estimated to be large with the subtractive method ~ (15) N total loss minus ammonia volatilization. The study also showed that alternation of dry and wet soils during rice cultivation and rice between the two seasons resulted in loss of nitrification-denitrification. It is still necessary in the future to further determine the amount of denitrification loss in soils that have been flooded and paddy soiled.