洱海流域典型农区不同施肥处理下稻田氨挥发变化特征

为探寻洱海流域合理的施肥方式,减少氮肥的氨挥发损失,采用"密闭室间歇通气法",研究了不同氮肥类型及施氮量对稻田氨挥发规律、氨挥发累积量及水稻产量的影响,并探究了影响氨挥发排放的因素。研究结果表明:稻田氨挥发主要发生在施肥后2～5 d内,穗肥期氨挥发损失占比最大为19.04%～33.00%,其次分蘖肥期损失为7.18%～15.72%,基肥期损失最少为4.89%～7.76%。不同施肥处理中常规施肥(CF)、化肥减量20%(T1)、单施有机肥(T2)、有机肥与化肥配施(T3)、考虑当季25%矿化率单施有机肥(T4)、考虑当季25%矿化率有机肥与化肥配施(T5)和单施控释肥(T6)的氨挥发累积量分别为42.52、22.73、11.71、15.12、38.24、25.95 kg·hm~(-2)和18.44 kg·hm~(-2)。等量施氮条件下不同肥料类型氨挥发损失占比大小为尿素控释肥有机肥+化肥有机肥。不同施氮量条件下,施氮量越大氨挥发累积量越大,且氨挥发速率与田面水NH4+-N浓度呈正相关性。综合稻田氨挥发累积量及水稻产量,在洱海流域典型农区水稻种植中,有机肥与化肥配施(25%当季矿化率)、化肥减量施用(20%)以及控释肥施用是3种较优的环境友好型施肥方式。

Characteristics of ammonia volatilization from rice paddy fields under different fertilization treatments in typical agricultural areas of Erhai basin

Ammonia (NH₃) volatilization is one of the major ways of nitrogen loss in paddy field. To reduce NH₃ volatilization and optimize fertilization scheme for paddy fields in the Erhai basin, effects of fertilizer types, nitrogen application rate and management strategies on NH₃ volatilization and rice grain yield were investigated using closed-chamber intermittent ventilation method. Correlation between NH₃ volatilization and soil characteristics were also evaluated. Results showed that, maximum NH₃ volatilization occurred within 2~5 days after fertilization. Moreover, the NH₃ volatilization loss accounted for 19.04%~33.00% at panicle growth stage, about 7.18%~15.72% at tillering stage, and about 4.89%~7.76% at basal stage. The NH₃ volatilization accumulations of conventional fertilization (CF), 20% nitrogen reduction (T1), refined organic fertilizers (T2), organic fertilizer and chemical fertilizer (T3), considering 25% mineralization rate of refined organic fertilizers (T4), considering 25% mineralization rate of refined organic fertilizers along with conventional fertilization, refined organic fertilizers + conventional fertilization (T5), and controlled release fertilizer (T6) were 42.52, 22.73, 11.71, 15.12, 38.24, 25.95 kg·hm^-2, and 18.44 kg·hm^-2, respectively. Under the same amount of nitrogen application, the proportion of NH₃ volatilization loss of different fertilizer types was:conventional fertilization > controlled release fertilizer > refined organic fertilizers + conventional fertilization > refined organic fertilizers. Nitrogen application rate in different treatments were directly proportional to the accumulated amount of NH₃. In addition, NH₃ volatilization rate was positively related to NH₄⁺-N concentration in the surface water. Considering the NH₃ volatilization accumulation and rice yield, compared with conventional fertilization, the treatments T1, T5 and T6 are environmentally friendly fertilization methods.