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Four-dimensional evaluation of nitrogen burden from agricultural and using Pedometrics

利用计步器对农业氮负荷进行四维评估

基本信息

批准号：
10460030
负责人：
KOSAKI Takashi
金额：
$ 8.77万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

To establish reasonable method for the evaluation of nitrogen burden from agricultural land to the environment, four-dimensional evaluation of nitrous oxide (N_2O) flux was carried out in a 1 ha agricultural land in Hokkaido, taking spatial and temporal variability of N_2O flux into account. For the spatial analysis, a hundred gas and soil samples were collected hm the field in August, 1999, and N_2O flux and soil physical, chemical fad biological properties were determined. N_2O flux had very high variability and showed moderate spatial dependency with the range of about 50m, suggesting that at least 9 measurements (every 50m) are necessary for the reasonable evaluation of N_2O flux in this field. N_2O flux was generally high at sites with relatively low elevation and was positively correlated with indices representing soil organic matter. For the temporal analysis, N_2O flux was also measured at one site for 5 years, i.e.from 1995 until 1999. N_2O flux was relatively low in spring after fertilization, and relatively high in summer and autumn, accounting for about 20% and 80% of the total emission, respectively. The mechanism of N_2O emission in spring was considered to be nitrification, and that in summer and autumn was considered to be denitrification at the relatively reduced sites in soil aggregates when a part of nitrate was accumulated due to source-sink effect of soil aggregate. A mechanistic model was further established to evaluate N_2O emission based on the estimation of"reduced volume in soil aggregate", and showed high positive correlation with the log-transformed N_2O flux.

为建立合理的农田氮素环境负荷评价方法，以北海道1 hm2农田为研究对象，考虑N2O通量的时空变异性，对其N2O通量进行了四维评价。为了进行空间分析，于1999年8月在该地区采集了100个气体和土壤样品，并测定了N2O通量和土壤物理、化学和生物性质。N2O通量具有很强的变异性，在50m左右的范围内表现出中等的空间相关性，这表明要合理地评价该区域的N2O通量，至少需要9次测量(每50m)。N2O通量在海拔较低的地点普遍较高，并与代表土壤有机质的指数呈正相关。在时间分析方面，还对1995~1999年在一个测点连续5年的N_2O通量进行了测量。施肥后春季N2O排放较低，夏季和秋季N2O排放较高，分别占总排放量的20%和80%左右。春季的N2O排放机制为硝化作用，夏秋季节由于土壤团聚体的源汇效应，部分硝态氮积累在相对减少的土壤团聚体中，属于反硝化作用。进一步建立了基于“土壤团聚体还原体积”估算N_2O排放的机理模型，该模型与对数转化的N_2O通量呈高度正相关。