【摘要】 为明确秸秆直接还田和秸秆炭化为生物炭后施入土壤对氮肥转化(植株吸收、土壤残留及损失)的影响,采用大田微区试验,运用15N标记示踪技术,分析了石灰性褐土施用生物炭和秸秆后氮肥的去向,并阐明其影响机制。试验共设3个处理,单施化肥(NPK)、施化肥并施生物炭(NPK+B)以及施化肥并施秸秆(NPK+S)。结果表明:石灰性褐土上高粱植株当季的氮肥吸收率、土壤残留率和损失率分别是18.41%～24.94%、22.67%～35.47%和46.12%～52.40%;与NPK处理相比,NPK+B和NPK+S处理高粱植株的氮肥利用率分别降低2.20个百分点和6.53个百分点(P<0.05),土壤残留率分别增加5.58个百分点(P<0.05)和12.80个百分点(P<0.05),氮肥损失率分别降低3.40个百分点和6.28个百分点(P<0.05);施用秸秆显著提高了土壤活性有机碳含量、土壤微生物数量及代谢活性,增强了氮肥转化过程中土壤微生物对肥料氮的固定,从而减少氮肥损失。因此,与施用生物炭比较,秸秆直接还田是提高石灰性褐土氮肥有效性及秸秆资源合理利用的更有效途径。更多还原

【Abstract】 【Objective】Nowadays, application of straw directly or after it is pyrolyzed into biochar is the main practice of straw resource utilization. However, how application of straw directly or after it is pyrolyzed into biochar affects transformation of nitrogen is still not clear.【Method】 A field experiment was carried out to explore effect of the application on transformation of fertilizer N in calcareous cinnamon soil and its possible mechanism. Sorghum uptake, residual in soil and losses of fertilizer N were studied using the 15 N isotope technique. The experiment was designed to have three treatments: NPK(chemical fertilizer only), NPK+B(chemical fertilizer with straw biochar), and NPK+S(chemical fertilizer with straw). 【Result】Sorghum nitrogen absorption rate, soil N retention rate, and N loss rate in the experiment was determined to be 18.4%～24.9%, 22.7%～35.5% and 46.1%～52.4%, respectively. Compared with NPK,NPK+B and NPK+S was 2.20 and 6.53(P<0.05) percentage point respectively lower in sorghum nitrogen absorption rate and 3.40 and 6.28(P<0.05) percentage point lower in N loss rate, but 5.58(P<0.05) and12.80(P<0.05) percentage point higher in soil N retension rate. Besides, NPK+B and NPK+S was 23.5%(P<0.05) and 4.3% respectively higher than NPK in content of soil organic carbon, 2.8% and 19.4% higher in soil labile organic carbon, 25.0% and 13.4% higher in population of soil bacteria, and 29.4% and 161.1%higher in population of fungi. Moreover, NPK+S was 103.7% and 72.8% higher than NPK+B and NPK in AWCD(Average well color development) value after 96 hours of incubation. 【Conclusion】In conclusion,application of straw or straw-derived biochar may reduce nitrogen absorption rate of sorghum, increase N retention rate, and lower N loss rate in the calcareous cinnamon soil. Application of straw significantly increases soil labile organic carbon, soil microbial population and metabolic activity, which in turn improves nitrogen transformation from nitrogen fertilizer to soil nutrient, and consequently reduces N loss rate. Straw returning or application o straw directly is an effective measure to improve availability of nitrogen fertilizer to the crop in the calcareous soil and promote reasonable utilization of the straw resources.更多还原