有机物料输入对干润砂质新成土可溶性有机碳、氮的影响

Effects of Exogenous Organic Materials on Dissolved Organic Carbon and Nitrogen in Ust Sandic Entisols

对采集于干润砂质新成土不同土层土壤分别添加高C/N(黑麦草)和低C/N(苜蓿)有机物料后进行了室内培养试验。结果表明,各土层土壤添加有机物料后,均存在不同程度的矿质氮微生物净固定现象,且氮固定时间及程度与有机物料的C/N和土壤层次密切相关,添加高C/N黑麦草的深层低肥力土壤氮固定现象最明显。添加有机物料后,培养期间可溶性有机碳(DOC)累积量前期较高,中期先减后增,后期趋于稳定,不同土层土壤DOC的变化有所不同。0～20、20～40cm可溶性有机氮(DON)累积同时受矿质氮固定影响,低C/N苜蓿残体加入土壤后,在短暂氮素固定后,后期DON累积量明显提高;而加入高C/N黑麦草残体后,在较长时间内DON累积量无明显增加。添加有机物料导致培养前期土壤DOC/DON上升,随后降低。以上研究结果表明,如果从增加干润砂质新成土土壤有机质角度考虑,应该种植高C/N比的植物。因此,研究有利于进一步深入理解土壤溶液速效C、N养分的来源及其转化,对该地区土壤质量的调控具有一定参考价值。

It has been found that dissolved organic matter（DOM） has significant effects on the migration and effectiveness of nutrients and thus could be considered as an index for evaluating soil quality.Therefore in order to know whether inputs of organic materials would change soil quality to some degree in the wind-water erosion crisscross region,a typical fragile eco-region,on the Loess Plateau,mineral nitrogen and DOM were selected as the main soil quality indexes.Using a laboratory incubation experiment under aerobic soil moisture conditions,we investigated the dynamic changes in the mineralization of soil organic nitrogen and the dissolved organic carbon（DOC） and dissolved organic nitrogen（DON） content for inputs of organic materials with different C/N ratios in Ust Sandic Entisols.The results showed that N-fixation occurred after the organic material with different C/N ratio was added,and that the fixation period was closely related to the soil layer and soil fertility because a longer fixation period was found in the deeper soil layer.The accumulation of DOC in different soil layers with added organic material,was highest in the early stage,decreased first and then increased in middle stage,and decreased to stable stage in later stage.The accumulation of DOC in the 0～20 cm,20～40 cm,40～60 cm soil layers came to the peak on the 28th day,42th day,56th day respectively.The accumulation of DON was obviously affected by N-fixation whereby it notably increased after a short period of N-fixation with the inputs of organic materials with lower C/N ratios.However,no obvious DON increase was observed with the inputs of organic materials with higher C/N ratios.The DOC/DON followed an increasing trend in the earliest stage but tended to decrease tendency in the later stage.These results suggest that available carbon and nitrogen was sensitive to the inputs of organic materials.Based on this experiment,it was found that growing plants with higher C/N ratios was beneficial to the increase of soil organic matter.Therefore,this study provides information for proposing adjustment measures to improve soil quality.