Evaluation Of Cultivated Land Productivity Of Qinba River Vallay Basin

This research is aimed to assess fertility and attributes of China’s farmland and based onthe assessment provides strategies and advice for improvement to each farmland. WithMianXian chosen as the study area, this research is supported by Geoway, ArcGIS and otherassessment systems for county level farmland resources, combined with delphi method,Analsis Hierarchy Process, and membership function, which are introduced to selectevaluation factors, and determine their weight and values, and eventually build membershipfunctions. Integrated fertility index for farmland,worked out by employing GIS data bank andaccumulative models, together with accumulative curve determined the grading of farmlandfertility.The cultivated land in MianXian is distributed primarily in its hilly regions in the middleand alluvial plain, and small amount of cultivated land is in mountainous regions. Farmlandarea from the plain is18380hm~2, amounting to up to half of the total arable land. Farmlandarea from the hilly regions is15016hm~2,39%of the total arable land. Farmland from the bothregions makes up87%of the total area. Gradient of the slope is another important factordetermining fertility. Most of the cultivated land is distributed in the regions with slopegradient between15°and25°, or below3°, of which15877hm~2,42%of the total area ofcultivated land, comes from slopes with gradient between between15°and25°. Only103hm~2cultivated land comes from slope with gradient of more than25°. The data indicatesthat fertility is closely correlated to the soil types, topography and geomorphology, and slopegradient. With the rise of the grade of fertility, geomorphological types graduate from fairlylevel alluvial plains, to hilly regions and mountainous regions at high altitudes, with theirdistribution clearly regional.Soil here in MianXian is diverse in type comprising paddy soil, silt soil, alluvial soil,yellow brown soil and brown soil. The paddy soil is the major type here with an area of15183hm~2which is commonly found in plain areas and hilly regions. In term of soil structure, ahigher proportion of soil is in the form of cluster and block, with granular aggregates second and grains least, so the comparatively optimum structure should contains less soil grains. Thestudy results show that the cultivated soil from MianXian has a relatively high content oforganic matters, averagely20.30g/kg，and mostly beyond15g/kg. The concentration ofAlkaline hydrolytic nitrogen in the soil is on average131.85mg/kg, and although it varies on arelatively large scale, it is most times between90-150mg/kg. With an average of15.15mg/kgavailable phosphorus content is between10-20mg/kg an interval58.59%of the arable landfalls in. Available potassium content ranges from70-100mg/kg with an average of97.93mg/kg. while less than2%of the arable land contains available potassium content below70mg/kg. PH values stay quite stable with an average of6.89, approximately neutral.The county’s has first grade arable land with an area of4708hm~2, amount to12%of thetotal area, most of which is found in low alluvial plains which enjoy good irrigation. Secondgrade land occupies an area of10810hm~2,28%of the total arable land and94%of it islocated in alluvial plains with small proportion found in hilly regions whose soil nutrientcontent is high and surface not clearly eroded. Third grade land area is6931hm~2,18%ofthe total cultivated land,54%of which is distributed in hilly regions with apparent erosionseen in part of these regions. Fourth grade land has an area of6330hm~2,17%of the totalcultivated land, commonly found hilly regions between alluvial plains and mountainousareas with relatively apparent erosion in major part of these regions. Fifth grade land occupies7341hm~2，19%of the total cultivated land, most of which is found in hilly regions whoseslope gradient is over10°. Land of this grade has the largest area of yellow brown soil andpaddy soil, silt soil of small area. Sixth grade land has an area of2112hm~2,6%of the totalarea. Land of this grade is distributed in mountainous areas with slope gradient over18°insouth and north. It’s covered with yellow brown soil.Given is advice on the future agricultural production in terms of soil improvement,reasonable allocation of the resources and management of quality of cultivated land. Throughthis research, we have gradually pioneered and worked out a set of approaches and technicalprocedures, which, combined with GIS, can effectively survey and assess cultivated landcapability, and play an active role in scientific management of cultivated land resources andsustainable development.