基于GIS和地统计学的不同尺度水稻田土壤养分时空变异及其机理研究

【作者】 刘杏梅；

【导师】 徐建明；

【作者基本信息】 浙江大学 ， 土壤学， 2005， 博士

【摘要】 管理好土壤养分,合理进行施肥,是关系到我国农业可持续发展的重大技术问题。土壤养分不仅具有明显的空间变异,而且在时间上也表现出一定的变化。杭嘉湖平原作为浙江省重要的粮食生产基地,其土壤养分的状况不仅与该区农业非点源污染等环境问题有关,更与水稻产量与质量息息相关。因此,了解该区水稻田土壤养分的空间和时间变异是精确农业管理的基础。但是长期以来,国内外关于土壤养分空间变异的研究大都集中在旱地土壤,且田间尺度研究较多,对大尺度下水稻田土壤养分的时空变异几乎是空白。本研究应用地统计学和GIS技术相结合的方法,以南方水稻田为研究对象,选择1:250000杭嘉湖平原、1:50000平湖市、1:2000同心村试验小区三个不同尺度研究区域,分析了水稻田土壤养分的时空变异及其机理,并进行不同尺度管理分区模式探讨。主要研究结果如下: 1.杭嘉湖平原水稻田土壤养分时空变异 2001年杭嘉湖平原水稻田土壤有机质、全氮、有效磷含量均比1982年第二次土壤普查时有所提高,而速效钾含量有大幅下降。整个杭嘉湖地区近20年来土壤养分的变化与该区施肥结构相一致,即氮肥施用量过多,磷肥次之,钾肥投入严重不足。因此,该区土壤养分供应严重失调,进而导致作物产量对化肥的依赖性增加。 中国土地政策自70年代末实行联产承包责任制以来,水稻田经过长期不同的人为耕作管理,其土壤有机质和全氮含量已逐渐趋向均一,有机质和全氮的变异系数均呈下降趋势,而有效磷和速效钾的变异系数都在近20年间有所增加,尤其是有效磷。 杭嘉湖平原2001年所有土壤养分均具有中等程度的空间相关性,说明经过长时间的耕作,施肥、耕作、田间管理水平等人为因素在一定程度上削弱了其受母质、地形、气候等非人为结构性因素的影响,从而削弱了它们的空间相关性。杭嘉湖平原土壤养分时空分布图结果进一步解释了有机质、全氮、有效磷和速效钾在近20年间的变化格局,为以后的农业管理提供了科学依据。水稻田土壤有效锌和有效铜等微量元素含量在大范围区域内表现出较大的变异性,空间分布不均匀。根据浙江省土壤养分分级标准,对2001年杭嘉湖土壤养分分布格局进行了宏观分区,有机质和有效磷分为三个管理分区,全氮、速效钾、有效锌和有效铜均分为两个管理分区,根据该管理分区,可以为以后农业生产的因地制宜精确管理以及作物种植结构调整等提供服务。 2.平湖市水稻田土壤养分时空变异 平湖市土壤有机质、全氮和有效磷含量在近20年间都有不同程度的增加,而速效钾呈下降趋势,更多还原

【Abstract】 Scientific management of soil nutrients and rational use of fertilizer are strategic issues affecting sustainability of Chinese agriculture. Soil nutrients not only have spatial variability, but also change with the time. With the rapid development of agriculture in Zhejiang province, the management of soil nutrients in Hangzhou-Jiaxing-Huzhou (HJH) water-net plain is directly connected with the crop yield and agricultural non-point source pollution. So, understanding the spatial and temporal variability of soil nutrients in paddy field is the foundation of precision agriculture management. There has been growing interest in the study on spatial variation of soil properties in dry land using geostatistics since 1970s, and geostatistics has also been well developed and is proved successful in characterizing the soil variation. While many studies have been carried out at a small scale, relatively few have been done at large scale, especially on paddy field. Geostatistics and GIS were used in this study to analysize the spatial and temporal variability of soil nutrients in paddy field and their mechanism under three different scales of HJH Plain (1:250000), Pinghu county (1:50000) and Tongxin test plot area (1:2000), meanwhile, the regionalized management was brought forward in this study. The main results obtained are summarized as follows:1. Spatio-temporal variability of soil nutrients in paddy field in HJH PlainThe contents of soil organic matter (SOM), total nitrogen (TN) and available phosphorus (AP) in HJH Plain increased from 1982 to 2001, whereas, that of AK decreased dramatically. This change was in consistent with the fertilization structure, excess application of N and less application of K fertilizer in this region.The Household Responsibility System initiated at the end of 1970s in China has brought a profound change to its rural economy. Farmland was allocated to each peasant household on the basis of family size, and farmers have been given the right to till the contracted land. The township governments allow the farmers of each household to make all the decisions about production. The shift from the collective farming system to individual family farms has changedthe type of land utilization and management. After long different land management, the content of SOM and TN has become more uniform than before. The CV value for SOM and TN was all decreased during the past 20 years, however, that for AP and AK increased.Semivariograms of the soil nutrients in HJH Plain in 2001 displayed that they were all moderately spatially dependent, which illuminated that the long history of soil management of the field had weakened the spatial variability determined by the characteristics of the soil properties. The spatial and temporal distribution maps of SOM, TN, AP and AK further explained the patterns of their change during the past 20 years, which lay the foundation of agricultural management in the future. There was strong spatial variability for soil available Zn and Cu under long distance. Based on the classification of soil nutrients in Zhejiang Province, regionalized management of soil nutrients in HJH Plain was analyzed. And the SOM and AP were divided into three regions and two regions for TN, AK, available Zn and Cu. The mode of regionalized management could aid for the precision agricultural management.2. Spatio-temporal variability of soil nutrients in Pinghu CountyThe spatio-temporal variability of SOM and nutrients in paddy field induced by land management change was apparent. Over longer history of land management of Household Responsibility System, the spatial variability of soil properties was determined by the characteristics of the soil properties and the history of soil management of the field. It is worthy to note that the fitted r~2 values for soil AP and AK in 2002 were very small, both semivariograms showed pure nugget effect with weak spatial dependence. This illuminated that the spatial variance between farmers owing to different land management was covered at large scale. These results ind更多还原