半干旱农田生态系统长期施肥对土壤有机氮组分和微生物体氮的影响

Effects of Long-Term Application of Fertilizers on Soil Organic Nitrogen Components and Microbial Biomass Nitrogen in Semiarid Farmland Ecological System

在半干旱农田生态系统红油土上20年的肥料定位试验表明,施用秸秆和厩肥会显著改变耕层土壤有机氮组分和微生物体氮。施肥后酸解性氮的含量及比例明显增加,非酸解性氮含量下降。酸解性氮在不施肥时含量最低(646.3 mgN·kg-1),其次为施用化肥(684.3 mgN·kg-1),同时施用秸秆和化肥居中(794.1～950 mgN·kg-1),施用厩肥和化肥最高(1 103.2 mgN·kg-1)。各处理中,酸解性氮是土壤全氮的主体,占全氮的 73.4%～82.6%,这一比例从仅施化肥、对照、化肥+ 低量秸秆、化肥 +中量秸秆、化肥+ 高量秸秆到化肥+ 厩肥呈增加趋势。休闲处理酸解性氮所占比例(81.0%)较种植处理(74.4%)高。在酸解性氮中,施肥影响最显著的是氨基酸氮,施肥后平均增加148.7 mgN·kg-1;其次是氨态氮,平均增加 45.8 mgN·kg-1。这两类酸解性氮组分在配施秸秆和厩肥后增加幅度较大,并随秸秆用量增加而增加。对不同氨基酸成分,施肥影响程度不同,施肥后中性氨基酸平均增加82.6 mgN·kg-1,碱性氨基酸平均增加 48.2 mgN·kg-1,酸性氨基酸平均增加 16.4 mgN·kg-1。不施肥处理微生物体氮为 102.1 mgN·kg-1,施用化肥为 107.4 mgN·kg-1。在施化肥的基础上,配施有机物料,微生物体氮显著增加:在每年每公顷施 9 375、18 750、37 500 kg 新鲜?

Soil samples collected from the 20-year long-term fertilizer experiment carried out on the manual loessial soil situated in semiarid farmland ecological system were used to study the soil organic nitrogen components and microbial biomass nitrogen. Results showed that the application of straw and manure could significantly change the organic nitrogen components and microbial biomass nitrogen, and the amount and proportions of acidic hydrolyzable nitrogen increased apparently after application of organic materials, but the amount and proportions of unhydrolyzable nitrogen decreased. Among acidic hydrolyzable nitrogen components, the effects of organic materials on amino acid nitrogen (the average increment was148.7 mgN·kg-1) and ammonia nitrogen (theincrement was45.8 mgN·kg-1) were themost significant with no fertilization, the microbial biomass nitrogen at 0-20 cm depth was 102.2 and 110.4 mgN·kg-1 with application of both N and P fertilizers, whereas addition of 9 375, 18 750, 37 500 kg fresh maize straw and 37 500 kg of organicmanure per ha peryear on the basis of applying N and P fertilizers raised the micrbial biomass nitrogen to 147.5, 163.2, 286.4 and 265.3 mgN·kg-1, respectively.The results of correlation analysis show that there existed a very significant positive correlation between microbial biomass nitrogen and acidichydrolyzable nitrogen after fertilizer application (r=0.901, n=7). In acidic hydrolyzable nitrogen, the correlation coefficient between microbial biomass nitrogen with amino acid nitrogen was largest (r=0.963), with ammonia nitrogen was larger (r=0.886), and the correlations between amino sugar nitrogen or unknown nitrogen and microbial biomass nitrogen did not reach to a significant level. No matter what the case was, amino acid nitrogen and ammonia nitrogen are the easiest mineralizable components of organic nitrogen, the relationship between microbial biomass nitrogen and easily mineralizable organic nitrogen components was most closely.