| The cultivated landinNortheastern Chinahas higher fertility with stronger providing capacity of nutrients,which is China’s important commodity grain base and plays a decisive role for the national food security.However,long-term extensive overuse hasresulted in soil erosion,quality decline ofcultivated land,and even environmental damage and other problems.Therefore,it is necessary to investigate and evaluate the quality of cultivated land in this region,to identify the main problems in the use of arable land,to provide scientific basis for the quality protection and upgrading of cultivated land,the rational utilization of cultivated land resources,and the sustainable development of economy and society.Based on the data for the evaluation of cultivated land fertility in Northeast China(Liaoning Province,Jilin Province,Heilongjiang Province,East Fourth Leagues of Inner Mongolia,and Heilongjiang Provincial Land Reclamation Bureau),this study has constructed 6 categories,a total of 13 indicators for cultivated land quality evaluation system.These indicatores included climate conditions,site conditions,profile traits,soil nutrients,soil physical and chemical properties and soil management.The quality of cultivated land in the region was graded by the combination of Delphi method and analytic hierarchy process.At the same time,according to the results of evaluated quality grades of cultivated land,they were classified into 3 levels,that is,high(1st to 3rdgrade),medium(4thto 7th grade),low(8th to 10th grade).The main limiting factors have been discussed and important promoting measures have been pointed out.The main findings are as follows:(1)The evaluation index system of cultivated land quality in northeast Chinahas been established.The system included the climatic conditions,site conditions,profile traits,soil nutrients,soil physical and chemical properties and soil management 6 categories,a total of 13 indicators.The Delphi and analytic hierarchy process have been used to determine the weight and divide the grades of cultivated land.(2)According to the standards from the Ministry of Agriculture,the cultivated land quality was divided into ten gradesin northeastern China.The 5th and 4thgrades of cultivated land accounted for 19.04%and 17.94%of the total area.Next were the 6th and 3rd grades,accounting for 14.28%and 13.48%,respectively.The 7th and 2nd grades accounted for 9.06%and 8.38%.then the 8th and 1st grades accountedfor 6.57%and5.84%.And the last were the 9th and 10th grades,accounting for 2.99%and 2.41%respectively.(3)According to the grades for high,medium and low quality of cultivated land classification,the high quality land accounted for 27.70%of the-total cultivated land area,the medium quality land accounted for 60.32%and the low quality land was 11.98%.The main limiting factors of the soil qualityin cultivated land have discussed.The main limiting factorsin the high quality cultivated land,included soil organic matter,tillage layer and drainage capacity.The main limiting factors for medium quality land were irrigation,drainage capacity,soil texture and profile configuration.And the main limiting factors for low cultivated land were available phosphorus,irrigation ability and profile configuration.(4)The corresponding improvement measures have beenput forward according to limiting factores in the different quality cultivated lands.For high quality land,methods were mainly focussed on the arable land conservation,soilorganic matter promotion,farmland water conservancy facilities’ management and protection.For medium quality land,methods were emphasized on increasing investment in farmland water conservancy projects,deep plowing and deepening combined with soil improvement and increase of organic fertilizers.For low quality cultivated land,the methods could befocussed on soil testing and fertilization,farmland water conservancy construction and regular plowing or soil combined with the application of organic fertilizer and other measures. |
