中国西南典型山区县级耕地地力评价与分级

Evaluation and Classification of Cultivated Land Fertility in Inaccessible Mountainous Areas of Southwest China

为客观掌握我国西南典型山区耕地地力的时空分布规律,为区域耕地的合理施肥和高效利用提供依据,以云南省华坪县为例,从影响耕地地力的土壤管理、立地条件、剖面与耕层理化性状、养分状况4个方面筛选13个评价指标,随机采集2515个土壤样品,借助GIS空间分析技术,引入基于Bootstrap算法的CART模型,并与模糊数学法相结合,构建地力综合指数模型对研究区耕地地力进行了定量评价及分级研究。结果表明:研究区耕地地力分为6个等级。其中,三级和四级耕地所占面积最大,分别占耕地总面积的30.39%和23.13%,并且随着等级的升高,各等级耕地中的灌溉水田面积逐渐减少;空间分布上,各等级耕地在每个乡镇均有分布,但由于地形地貌、成土母质、土壤质地等存在空间差异,每一等级的耕地在各个乡镇的分布也存在较大差异,总体上耕地地力呈现以河谷为中心向四周放射状衰减的趋势,且随着等级的升高土壤肥力明显下降、土地利用的受限性也逐渐增多。因此,建议一二三级耕地在利用上注重科学施肥,加深熟化土层,四五六级耕地重点做好水土保持,有条件的地方应积极推进坡改梯工程建设,部分坡度过大的耕地,可考虑退耕还林还草。评价结果对于解析我国西南相似区域内的中低产田主要障碍因子、开展地力定向培育和农田精准管理具有重要现实意义。

In order to master the rules of spatial and temporal distribution for the cultivated land fertility in the inaccessible mountainous areas of Southwest China,and to provide a basis for rational fertilization and efficient utilization of regional cultivated land,the paper cites Huaping County as a case study,and 2515 soil samples of cultivated land were randomly collected.Then 13 evaluation factors were selected by using GIS,CART model based on bootstrap algorithm combined with the Fuzzy Mathematics,to evaluate cultivated land fertility classes and spatial distribution.The results showed that the cultivated land fertility in the study area is divided into six classes.Among them,area of the cultivated land of class 3 and class 4 is the largest,accounting for 30.39%and 23.13% for the total areas of the cultivated land respectively,and with the increase of the classes,the irrigated paddy fields area of each class of cultivated land decreased gradually.From the spatial distribution,each class of cultivated land is distributed in each town,but because of the regional topography,soil parent material,soil texture exists spatial difference,the distribution of each class of farmland is a big difference in different towns,then the cultivated land fertility shows the general trend of decaying the radially around the river valley as a center.Besides,the soil fertility declined obviously and the land use limitation increased gradually with the increase of the classes for cultivated land fertility in the county.So,as far as improvement of soil fertility is concerned,the cultivated land of the class 1,class 2,and class 3 should pay attention to scientific fertilization,and deepen the maturing of the soil layer,but the cultivated land of the class4,class 5 and class 6 should focus on the conservation of water and soil.In addition,areas have conditions should also actively to promote engineering of changing mountain slop into terrace field,especially for some cultivated land with much sloping land,the conversion of cropland to forest or grassland may be considered.The evaluation results have important practical significance for analyzing some main obstacle factors of low and middle yield fields,carrying out the directional cultivation of soil fertility and precise management of cultivated land in the similar areas of Southwest China.