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秸秆还田是农业生产上提高土壤肥力的重要措施,而秸秆中较高的碳氮比,使秸秆碳的利用率较低,温室气体排放较高,因此配施无机氮磷肥能够调控土壤中元素计量比,增加微生物活性和元素利用率,促进土壤肥力提升.本研究选择在模拟秸秆还田条件下,添加~(15)N标记的无机氮肥,研究不同养分肥料添加对土壤中外源氮转化与分配的影响,以及微生物响应特征.结果表明,秸秆添加增加了土壤和土壤溶液中铵态氮和总氮含量;秸秆与无机氮肥配施条件下,土壤中~(15)N-TN在100 d培养时期内基本保持在28~33μg,~(15)N-NH+4在前30 d培养时期内逐渐增加,而后逐渐降低;施P增加了土壤中~(15)N-TN和~(15)N-NH+4的含量,却使土壤溶液中~(15)N量降低了28%.无机氮肥在土壤中的分配表明,~(15)N在土壤中的比例基本保持在52%~61%,磷肥的添加使~(15)N在土壤中的分配比例最大提高了16.5%,而土壤溶液中~(15)N的比例由第5 d的36%降低至100 d时30%,使外源~(15)N损失量减少了1.2倍.秸秆添加促进了微生物活性,显著提高了土壤MBN的量;而无机肥料的添加进一步促进了土壤微生物的活性,100 d培养实验后,秸秆与无机氮、磷肥同时添加使MBN增加到对照处理的2.0和2.2倍.磷肥添加促进了微生物对~(15)N的利用,使~(15)N-微生物生物量氮(~(15)N-MBN)的量比添加秸秆和氮肥处理的提高了1.5倍.对土壤氮转化酶活性(β-1,4-N-乙酰葡糖氨糖苷酶,NAG)的研究结果表明,氮肥降低了土壤酶活性和底物亲和性,而氮磷肥同时添加时,酶活性较单加秸秆处理提高了48.1%.本研究可为深入了解稻田土壤生态系统氮循环、实现农田土壤肥力提升和温室气体减排提供理论依据.
Straw return to farmland is an important measure to improve soil fertility in agricultural production. However, the higher ratio of carbon to nitrogen in straw makes the carbon utilization rate of straw lower and the greenhouse gas emissions higher. Therefore, the application of inorganic nitrogen and phosphorus fertilizers can regulate the contents of soil elements (15) N labeled inorganic nitrogen fertilizers were selected to study the effects of different nutrients and fertilizers on the transformation of exogenous nitrogen and total nitrogen in soils The distribution and the characteristics of microbial response.The results showed that the addition of straw increased the content of ammonium nitrogen and total nitrogen in soil and soil solution.Under the condition of straw and inorganic nitrogen fertilizer application, During the cultivation period, the content of ~ (15) N-NH + 4 gradually increased in the first 30 days and then decreased gradually; ) N-NH + 4 decreased the amount of ~ (15) N in the soil solution by 28% .The distribution of inorganic N fertilizer in the soil showed that the proportion of ~ (15) N in the soil remained at 52% 61%. The addition of phosphate fertilizer increased the proportion of ~ (15) N in the soil by 16.5% N decreased from 36% on the 5th day to 30% on the 100th day, which reduced the loss of exogenous 15% N by 1.2 times.The straw addition promoted the microbial activity and significantly increased the amount of soil MBN, The addition of fertilizers further promoted the activity of soil microorganisms, and the addition of straw and inorganic nitrogen and phosphate simultaneously increased the MBN to 2.0 and 2.2 times that of the control after 100 days of cultivation. The application of phosphate fertilizer promoted the utilization of 15 N by microorganisms (~ (15) N-MBN) increased by 1.5 times than that of adding straw and nitrogen fertilizer.The soil N-converting enzyme activity (β-1,4-N- NAG) showed that nitrogen fertilizer decreased soil enzyme activity and substrate affinity, while the enzyme activity was increased by 48.1% compared with single straw treatment when the nitrogen and phosphorus fertilizers were added at the same time. In-depth understanding of paddy soil ecosystem nitrogen cycle, to achieve improvement of farmland soil fertility and greenhouse gas emissions provide a theoretical basis.