Evaluation Of Farmland Productivity In Complex Topography Regions Of Guanzhong Area

Cultivated land is the essence of soil. It is the irreplaceable means of production of foodand other agricultural products. Farmland fertility level directly decides the quantity andquality of food. The21st century brought the rapid development of economy, largerpopulation and higher living standard, as well as people’s increasing demand for food quantityand quality. Meanwhile the acceleration of industrialization in modern society leads to thedecrease of cultivated land area. We are able to figure out the farmland productivity in thespecific area through farmland productivity assessment. It has important practical significancein farmland management and protection, agricultural restructuring and agricultural sustainabledevelopment.In order to learn the features and distribution of county farmland productivity,2931soilsamples were collected from soil layers with depth of0~20cm in22towns’ farmlandsthrough field survey and indoor soil sample analysis. By the domain method to identifyspecific values as well as the method of neighbouring points comparison, abnormal valueswere removed and2808valid soil samples were finally reserved. After obtaining theevaluation information of farmland productivity, farmland productivity of Lantian County wasevaluated quantitatively using GIS, synthetical index method and relevant models. Thesuitability of growing wheat and corn and the enrichment and the paucity of soil nutrient werealso analyzed.（1）The results showed that the total cultivated area of Lantian County was61472.71hm2, accounting for30.8%of the total area. The areas of the1st,2nd,3rd,4th and5th gradecultivated land take the percentage of15.6%，35.7%，29.0%，17.1%and2.6%of the total areaof the cultivated land. The geomorphic type had an obvious influence on the farmlandproductivity.1st grade and2nd grade were concentrated in the valley terrace and loesstableland, while3rd,4th and5th were mainly distributed in the low-relief terrain. The area of2nd grade was the largest and5th grade was the smallest.（2）There were10kinds of surface soil in research district. Lou soil, cinnamon soil andloessal soil were the main types, the area of which was41065.13hm2, reaching66.8%of totalarea of surface soil. They mainly distributed in valley terrace, loess tableland and pluvial fan station tableland. Soil structure in the study area was mainly composed of granule with thearea of16307.66hm2, reaching26.53%of total area of surface soil. The secondary soilstructure in the study area was prismatic structure, with the area of11814.48hm2, reaching19.22%of total area of surface soil. Soil texture of this area was mainly medium loam, withthe area of23563.46hm2, reaching38.32%of total area. The secondary soil texture in thestudy area was medium-light loam, with the area of16853.10hm2, reaching27.42%of totalareal. The structure and texture were good and water, ferterlizer, air and tempreture could beadjusted well.（3）The area of farmland with suitable altitude reached21.63%of total area while thearea of farmland suited for growing wheat (corn) reached36.44%of total area. They weremainly located in valley terrace of Ba River, pluvial fan station tableland in front of mountainand on the loess tableland. Others were fragmentarily located in the Northeast and Southwestlow-relief terrain. The less suitable area was35.15%, mainly located in loess tablelandNorthwest and Southwest of the county. The area that was not suitable for wheat or corn tookthe percentage of6.78%, fragmentarily located in the North, Northeast and Southwestlow-relief terrain.（4）The results of the enrichment and the paucity of soil nitrogen indicated that95.15%of the area did not lack nitrogen and could basically grow wheat and corn. The results of theenrichment and the paucity of soil available phosphorus showed that44320.08hm2of wheatgrowing region was lack of phosphorus, reaching72.10%of the total area. Thus availablephosphorus was an important fator in wheat yield. The corn had a lower requirement foravailable phosphorus, most rigion could meet the requirement of corn regular growth. Theresults of the enrichment and the paucity of soil available kalium indicated that “extremeenrichment” and “enrichment” area was45551.11hm2, reaching74.10%of the total area. The“extreme enrichment” area concentrated in Xiaozhai Town, while the “enrichment” regiondistributed in the whole county. The content of available kalium could meet the growingrequirement of wheat and corn well.