氮肥水平对不同土壤CH4排放的影响

鉴于氮肥施用对农田CH₄排放的影响还有很大不确定性,室外盆栽试验于2002年在南京农业大学实施.选取3个供试土壤,各土壤设置对照和低、中、高3个不同氮肥水平,施入尿素量分别为0 g/盆钵(对照) ,0.64g/盆钵,(低氮水平) ,1.28g/盆钵(中氮水平) ,1.93g/盆钵(高氮水平) .结果表明在水稻生长季,不同氮肥(尿素)施用量对稻田土壤CH₄排放影响表现为不同土壤之间,及不同氮肥水平之间CH₄排放均存在显著差异.无氮肥施入的情况下,3种土壤的CH₄季节性累积排放量存在显著差异,分别为6.7g/m²,12.6g/m² 和8.3g/m².施加氮肥后,3种土壤的CH4排放量随氮肥施入量的增加,均表现为降低趋势,不同土壤CH₄排放量存在差异,土壤背景氮含量最高的F(江苏溧水)土壤的CH4排放都比相应氮肥水平下的G(江苏涟水)和H(江苏农科院)土壤的CH₄排放低1倍左右.更进一步发现从低氮到中氮水平,3种土壤CH₄排放量随氮肥用量的增加降低幅度最大,而此时各土壤的NH₄-N含量随氮肥用量增加明显提高,推断造成CH₄排放降低的主要可能原因是各土壤的氨态氮含量的增加所致.从中氮到高氮水平3种土壤的CH₄排放量的变化不尽相同,G和H土壤的CH₄排放量随氮肥用量的增加而降低,而F土壤在中氮和高氮水平下的CH4排放量没有明显变化,值分别为30g/m².

Impact of Different Levels of Nitrogen Fertilizer on CH4 Emission from Different Paddy Soils

To investigate the effect of different urea incorporation amount in different soils on CH₄ emission, a pot experiment was carried in 2002. Four treatments were designed as the control (without urea incorporation); low N fertilizer level(0.64g urea/pot); middle N fertilizer level (1.28g urea/pot); high N fertilizer level (1.93g urea /pot). During rice growing season, incorporation of urea into different soils yielded different influence on CH₄ emission. Without urea incorporation, significance differences existed among CH₄ emission flux of three soils, with the values of 6.7g/m²,12.6 g/m² and 8.3 g/m², respectively. Incorporation of urea reduced considerably CH₄ emission of three soils. A further investigation indicate that CH₄ emission of three soils largely decreased and three soils NH₄⁺-N content obviously increased from low N fertilizer level to middle N fertilizer level. It concluded that soil NH₄⁺-N content is a key influence factor on CH₄ emission after incorporation of urea into soils. From middle N level to high N level, CH₄ emision of soil G(Lianshui,Jiangsu) and H(Jiangsu Academy of agricultural sciences) reduced, while CH₄ emision of soil F(Lishui,Jiangsu) had no obvious significance with the value of 3.0g/m² and 3.4 g/m².