关中盆地县域农田土壤碱解氮空间分异及变化研究

Study on Spatial Variability and Change of Soil Alkali-hydrolyzable Nitrogen in Guanzhong Basin County-level Farmland

论文以陕西省兴平市为例,采用2009年实测的耕层土壤碱解氮数据,运用地统计学结合GIS技术,建立其最佳半方差函数模型,分析关中盆地农田土壤碱解氮的空间特征、丰缺状况及其含量变化,为土壤培肥和农业生产提供理论基础。结果表明:研究区土壤碱解氮含量介于7.70～82.60 mg.kg-1,多集中在30～40 mg.kg-1,平均37.76 mg.kg-1,较第二次土壤普查下降28.62%。在间距约300 m的采样尺度下,最优理论模型为指数模型,表现为弱的空间相关性,施肥管理、种植制度等随机因素起主导作用。含量高低区域分布明显,大致呈中间高四周低格局。72.67%的农田氮素缺乏,27.33%的农田氮素含量中等。近30 a,原土壤碱解氮1～3级农田区含量显著下降,原5、6级区有所改善,整体集中于4级水平。应进一步实地考察分析具体障碍因素,积极采取分区"补氮"措施。

With Xingping County in Shaanxi Province as the research site, geostatistics and Geo graphical Information System （GIS） were employed to establish the best semivariance theory model and to study the spatial distribution, sufficiency and deficiency pattern, and content chan ges of soil alkalihydrolyzable nitrogen （AN） at county scale based on the 1651 topsoil samples taken by ＂Sshaped＂ methods in 2009, so as to provide theoretic guidance for soil fertilization management and agricultural industry in Guanzhong Basin. The result showed that soil AN content in the study area ranged from 7.70 mg kg1 to 82.60 mg kg1, concentrated at the level of 30 40 mg kg with an average of 37.76 mg kg which decreased by 28.62% compared to that recorded in the 1980s. AN content satisfied the normal distribution after BoxCox transforma tion （p = 0.35） with KolmogorovSmironov （KS） test. Under about 300m sampling scale, soil AN demonstrated weak spatial dependence was mainly affected by human factors including fertili zation, cropping systems and so on. There is obvious spatial difference in AN content distribu tion, which is shown as high in the center, while low in the surrounding areas. In the year of 2009, according to the abundant degree of soil AN content in Xingping County, 27.33% of farm land has proper AN content （40 60 mg .kg-1）, but as high as 72.67% （below 40 mg . kg-1） is lack of AN. According to the Second Soil Alkalihydrolyzable Nitrogen Classification Standard of Xingping, during the past 3 decades, the AN content in previous 1 3 grades farmland de creased sharply, but increased in the previous 5th and 6th grades farmland, and finally concen trated at the 4th grade. A total of 26. 17% of the farmland AN content grade changed, of which 22.68% of the farmland decreased significantly. The decreasing trend of soil AN content might be attributed to the reducing of nitrogen fertilizer and incorrect agronomic measures. It is necessary to conduct further field survey to collect the key limiting factors where soil AN content was low or reduced sharply and take measures timely to increase soil AN content.