Soil Fertility Improvement Of The Typical Northeast Black Soil Area Based On The Cultivated Land Fertility Evaluation

Cultivated land is the most important resources of agricultural production and is essential to the survival of human and the development of society.The quantity and quality of cultivated land have important influence on food security and social stability.The black soil area in Northeast China is one of three areas in the world,distributed mostly in the provinces of Heilongjiang,Jilin and Liaoning.Meanwhile,the typical area of black soil in Northeast China is the crucial to the national food security.Taking the typical area of black soil in Northeast China as research area,this study conducted the evaluation of cultivated land fertility by selecting 13 soil-affected factors from six aspects included climate condition,site condition,profile characteristics,physic-chemical property,plant nutrient and land management by means of the methods of analytic hierarchy process(AHP)and fuzzy mathematics.The cultivated land fertilities were evaluated and divided into 10 grades.Based on the degrees of influence and improvement of cultivated land fertility at present,six obstacle factors included top layer thickness,organic matter,available phosphorus,pH,irrigation ability and drainage ability were selected to analyze the obstacle degree.Using the modified obstacle degree model,the obstacle degree types of the improvement of cultivated land fertility among medium to high,low to medium,and low to high were analyzed.The obstacle degree in cultivated land fertility of study area was divided into four grades by means of equal interval method included non-obstacle degree,mild obstacle degree,moderate obstacle degree,and serious obstacle degree.Based on the analysis of obstacle degree,the countermeasures about improving cultivated land fertility were put forward.The results were as follows:(1)The total cultivated land area in the typical area was 8.25 million hm2,dominated by the grades from the second to sixth of cultivated land fertility that accounted for 12.58%,11.71%,16.16%,20.66%and 22.00%in total cultivated land area,respectively.Grouping the cultivated land fertility as high level(from grade 1 to 3),medium level(from grade 4 to 7)and low level(from grade 8 to 10),we found that the cultivated land fertility was dominated by medium level,accounting for 5.54 million hm2(67.15%),followed by the high level accounting for 2.36 million hm2(28.63%),and the lowest distribution was the low level accounting for 0.34 million hm2(4.22%).(2)The spatial distribution characteristics of cultivate land fertility presented an obvious trend of high in south and low in north.The high level of cultivated land mainly distributed from the south of Wuchang in Hei Longjiang Province to the Changtu country in Liaoning Province.The medium level mainly distributed from the north of Wuchang to the south of the large area of Nenjiang country.The low level farmland dispersedly distributed in the counties of Nenjiang,Wu Dalianchi and Yian.(3)The obstacle degree of cultivated land fertility improvement in study area was mainly in mild degree,showing a good condition of cultivated land.Moreover,the difference of obstacle degree between adjacent cultivated land fertility levels was little,showing that the improvements of cultivated land fertility between adjacent fertility levels should be easy.To be specific,however,there was difference between fertility levels,showing that the obstacle degree of cultivated land fertility improvement was dominated by mild degree from medium fertility level to high,and from low to medium.But it was dominated by serious level from low to high.These suggested that adjacent level of cultivated land fertility was easy to improve,while across level was difficult.In addition,there were differences among the obstacle factors of cultivated land fertility improvement in different regions.Therefore,the suitable measures and solutions on cultivated land fertility improvement should be carried out to meet local conditions.