长期不同施肥稻田土壤的氮素形态及矿化作用特征

Characteristics of nitrogen forms and mineralization in paddy soils of long-term fertilization experiment

利用稻田长期定位试验点的土壤样品,研究不同施肥稻田土壤的氮素形态及矿化作用特征.采用酸水解-蒸馏法测定土壤酸解总氮(TAHN)及其各组分含量;淹水密闭培养法测定土壤净矿化氮量(NMN).结果表明:①稻田土壤TAHN是全氮(TN)的主体(64%～73%),各施肥处理均显著提高其含量.单施无机肥处理对微生物量氮(MBN)、氨基酸氮(AAN)、酸解铵态氮(AN)、氨基糖氮(ASN)和酸解未知氮(HUN)的含量影响不大;无机配施有机肥显著提高各形态氮的含量;无机配施秸秆处理显著提高MBN、AAN、AN的含量.②14周的淹水密闭培养中,各施肥处理土壤NMN均随培养时间的延长而逐渐增加,矿化速率于培养3、4周后分别达到最大值.无机配施有机肥或秸秆处理土壤氮的矿化量、矿化率及矿化速率均高于单施无机肥处理.③相关性分析表明:土壤NMN与TN、TAHN、MBN存在极显著正相关关系;NMN与TAHN中各组分均存在正相关关系.进一步作多元回归分析表明:随着土壤氮矿化作用的增强,AAN和HUN的贡献增大,MBN对氮矿化也有重要的贡献.

Characteristics of nitrogen（N）forms and mineralization affected by long-term applications of inorganic fertilizers and organic manure or straw in paddy soils were investigated.Soil samples were collected from the plough layer of a long-term field experiment located at Wugang County,Hunan Province.Soil organic N was fractionated by acid hydrolysis-distillation method,and N mineralization was estimated by using 98-day anaerobic incubation at 30℃.The results showed that：i）Total acid hydrolysable N（TAHN）accounted for 64% to 73% of the total N（TN）in the paddy soils.Compared to CK,application of inorganic fertilizers had no significant effects on microbial biomass N（MBN）,amino acid N（AAN）,ammonium N（AN）,amino sugar N（ASN）,and hydrolysable unidentified nitrogen（HUN）.Application of NPK plus manures significantly increased contents of all organic N fractions,and application of NPK plus straw increased the contents of MBN,AAN and AN compared to that of inorganic fertilizers or CK treatment.ii）The amounts of net mineralized N（NMN）increased with the prolongation of incubation time,and ranged from 0.214 to 0.482 mg·g^-1 after 98-day anaerobic incubation.The rates of N mineralization were highest at the 3rd or 4th week incubation for different treatments.The rate of mineralization and the ratio of NMN to TN in NPK plus manure or straw treatments are greater than that of inorganic fertilizers treatments.iii）Significant correlations were found between NMN and TN,TAHN,MBN.NMN was also positively correlated with fractions of TAHN.Regression analysis further revealed that AAN and HUN were the significant variables in the multiple equations in relation to NMN,and MBN also made great contribution to NMN.