长期有机培肥模式下黑土碳与氮变化及氮素矿化特征

土壤氮的矿化是土壤氮素肥力的重要指标，是影响作物产量至关重要的因素。本研究依托黑土长期定位试验，通过取样分析研究了32 a不同培肥模式下黑土碳、 氮及主要活性组分的变化，采用淹水培养法研究了不同施肥模式下黑土氮素的矿化特征。结果表明，施肥显著提高黑土可溶性碳（DOC）、 氮（DON）的含量及其比例。在氮、 磷、 钾化肥的基础上配施有机肥，显著降低了土壤微生物量氮（SMBN）占土壤总氮的比例，提高了土壤微生物量的C/N比值（SMBC/SMBN），促进了土壤氮的生物固持。施肥32 a后，单施常量和高量有机肥处理的土壤氮的矿化量（Nt）显著提高，分别相当于不施肥的8.2倍和10.2倍，而单施氮或氮磷钾化肥对黑土氮素矿化量无明显影响。施用有机肥显著提高了土壤氮素的矿化率（Nt/TN），但有机肥配施化肥（氮或氮磷钾）的处理与单施有机肥相比，黑土氮的矿化率显著降低，降低幅度分别为23.5%~32.1% 和14.1%~17.8%。土壤氮素矿化量与土壤有机质、 全氮储量、 活性碳、 氮组分均呈极显著线性相关，但氮素的矿化率随着有机质和全氮含量的提高而提高至0.4% 后基本稳定。表明尽管土壤氮的矿化与有机质的含量直接相关，但土壤有机质的品质同样决定着土壤氮素的矿化能力。施有机氮是提高土壤供氮能力的重要途径。

Changes of soil carbon and nitrogen and characteristics of nitrogen mineralization under long-term manure fertilization practices in black soil

 Soil nitrogen mineralization is an essential index for soil nitrogen fertility and one of the important factors of regulating crop productivity. Based on a long term experiment in black soil, we analyzed changes of soil total and labile organic carbon and nitrogen after 32 years of various fertilizations. Soil nitrogen mineralization after 32 years of fertilization practices was estimated by anaerobic incubation method. Results show that the fertilization could significantly increase both the concentrations and ratios of dissolved organic carbon and nitrogen (DOC and DON). The application of chemical NPK fertilizers combined with organic manure significantly decreases the ratio of soil microbial biomass nitrogen to soil total nitrogen, increases soil microbial biomass C/N ratio (SMBC/SMBN), and promotes the biological fixation of soil nitrogen. The amounts of soil mineralized nitrogen are increased by 7.2 and 9.2 times under the moderate and high application rates of manure, respectively. However, the application of chemical fertilizers (N or NPK) has no effect on black soil nitrogen mineralization. After the application for 32 years, soil nitrogen mineralization amounts (Nt) are largely enhanced with the application of moderate and high rates of manure alone. The application of organic manure could significantly enhance soil nitrogen mineralization rate (Nt/TN). However, compared with the manure fertilization alone, additional application of chemical N fertilizer and NPK fertilizers decreases the Nt/TN rate by 23.5%-32.1% and 14.1%-17.8%, respectively. There are strong linear correlations between soil mineralized nitrogen amount and soil organic matter, soil nitrogen and labile fractions. The soil nitrogen mineralization rate is improved with the increase of organic matter and total nitrogen stock, and then is stable at 0.4% level. These results indicate that, even the amount of soil nitrogen mineralization is directly related to the amount of organic matter, soil organic matter quality also regulates the nitrogen mineralization capacity. Moreover, organic nitrogen application is the most important practice of enhancing soil nitrogen fertility.