麦秸全量还田下太湖地区两种典型水稻土稻季氨挥发特性比较

利用原状土柱在田间试验条件下,比较了麦秸还田下乌栅土和黄泥土稻季氮素氨挥发损失规律,每种试验土壤均设对照、氮肥、氮肥加麦秆这3个处理,同步测定施肥后氨挥发、田面水铵态氮浓度与pH、以及表层土壤Eh.结果表明,乌栅土氨挥发速率及其累积氨挥发量显著高于黄泥土,两种土壤的稻季平均氨挥发的氮素损失量分别为41.8 kg·hm-2和11.2kg·hm-2,分别占氮肥用量的15.2%和3.8%;在3个施肥时期中,分蘖肥期氨挥发损失率最高,乌栅土和黄泥土分别占氮肥用量的29.4%和8.3%;麦秸还田显著增加了氮肥的氨挥发损失,麦秸还田下乌栅土和黄泥土稻季氨挥发损失比单施氮肥处理分别增加了19.8%和20.6%.两种土壤氨挥发速率均与田面水NH4+-N浓度、pH呈正相关关系,但与表层土壤Eh的关系还需进一步研究.

Comparing the Ammonia Volatilization Characteristic of Two Typical Paddy Soil with Total Wheat Straw Returning in Taihu Lake Region

An experiment using monolith lysimeter was conducted to compare the characteristic of N loss by ammonia (NH₃) volatilization between the gleyed paddy soil (G soil) and hydromorphic paddy soil (H soil) the Changshu National Agro-ecological Experimental Station of the Chinese Academy of Sciences(31°33' N, 123°38' E). Three treatments were designed for each soil type, i. e. control (no urea and straw applied), nitrogen solely and nitrogen plus wheat straw. Ammonia volatilization, flood water NH₄⁺-N concentration,pH and top soil Eh were measured during the rice-growing season. Results showed that the NH₃ volatilization flux and cumulative N losses by NH₃ volatilization from G soil were significantly higher than those from H soil, the average cumulative N losses being about 41.8 kg·hm^-2and 11.2 kg·hm^-2, or 15.2% and 3.8% of the fertilizer N, respectively. The average N loss by NH₃ volatilization during the tillering stage was the highest among the three fertilization stages, accounting for 29.4% and 8.3% of the fertilizer N for G soil and H soil, respectively. Wheat straw returning significantly increased paddy filed NH₃ volatilization losses. Comparing with the sole application of fertilizer-N, the cumulative N loss by NH₃ volatilization of fertilizer-N in combination with wheat straw was increased by 19.8% and 20.6% for G soil and H soil, respectively. In addition, ammonia volatilization fluxes showed a positive relationship with the flood water NH₄⁺-N concentration and pH for both soils, but the relationship with top soil Eh still needs further study.