| Agriculture sustainable development has been a basic national policy in China.The central rural work conference on December 23,2013 proposed a slogan "to ensure food security,to adhere to the red line of 1.8 billion Mu arable land",and pointed out it was the primary task of the national economy in 2014,among which the status of the agricultural system in northern arid areas should not be underestimated.Agro-pasturage ecotone in the north of China is an ecological complex,including interleaving,inserting natural grassland community and artificial farmland community,which have a huge production potential.It is an green barrier to prevent desertification to the east and south.Naiman County is located in the southern margin of the horqin – a typical Agro-pasturage ecotone zone,in which agricultural land is occupied 24.25% in the land use types,but 70.2% of the total population mainly engaged in agriculture,which means a stronger reliance on agricultural land.Adverse natural environment and unreasonable human activities aggravated the agricultural land quality in this region,so it is urgent to improve the quality agricultural land;It is by identifying the differences in agricultural land quality from various angles,keeping the high-quality agricultural land,remedying the inferior quality agricultural land,and managing multi-levelly partition based on agricultural land quality that has great guiding significance to adjust the agricultural land layout and use land resources efficiently and rationally meanwhile,becomes the best way to solve the food security.The agricultural land quality grade is calculated by using Inverse Distance Weighted,agriculture land quality classification and gradation method and the temporal and spatial variation pattern in 4 years in 15 town of Naiman county is discussed in this paper,combining with agricultural land characteristics,based on 17 indicators,such as the effective phosphorus and effective potassium,soil erosion,landform,farmland infrastructure so on.Meanwhile,the weight of change concept,the entropy method and PCA are used to determine the weight.The main conclusions of this paper are as follows:(1)The agricultural land in Naiman county can be divided into four levels,sorting as level 4 > level 3 > level 1 > level 2,the proportion respectively was 29.21%,25.98%,22.15%,22.66%.Level 1 agricultural land are mainly distributed in the central and northeast,in the periphery of which are distributed the level 2 agricultural land,the level 3 distributed in the periphery of the central and the level 2,the level 4 agricultural land distributed in the southeast mountain area.(2)The temporal variation characteristics of agricultural land quality showed that level 1 and level 4 was decreased first then increased,in which level 1 decreased from 18% to 16% and then rose to 23%,level 4 was reached to 34% in 2006,and the stability at 26% from 2009 to 2012,then gradually increased to 29% in 2015;The level 2 has increased from 23% to 26% by the year 2009,then fell to 22%;The changing trends of level 3 is similar to level 2,reached to 34% in 2012,and then declined to 26%,the increase of the level 2 and level 3 effectively relieve the differences between agricultural land quality and level assignment tends to be uniform.(3)The spatial variation characteristics of agricultural land quality showed that,from 2006 to 2015,it declined from the northern and central near the river of flat areas to the surrounding areas and the peripheral of the south in Naiman county,leading a corresponding improvement in the surrounding areas.The level 1 agricultural land area in the north increased 81.08Km2,and the level 6 reduced 153.45Km2 in the south.However,the number of high-quality agricultural land is still scarce,the difficult-used agricultural land is numerous,the area respectively was 596.68Km2 and 1109.81Km2;Sandy areas and mountainous areas are facing degradation crisis which has the characteristics of fragile natural conditions,lack of stability and difficult governance.Agricultural land in mountainous area is diminishing from 1019.72Km2 to 731.12Km2,and at the same time,the sum of the area of forest land and grassland was soared from 649.31Km2 to 1032.24Km2,which utilization quality is obviously better than agricultural land.As to the respect of economic quality distribution,the natural condition and social economic conditions in Da Qin Ta La town and northeast areas are very conducive to the development of agriculture,accounting for 44.8% of the total area,gradually reducing to the external areas and the level 4 agricultural land has reduced 248.28Km2 in the south.(4)The influence of social and economic factors in the evaluation index system gradually goes beyond the natural factors,and the weight of the three indicators,such as the probability of irrigation,the farmland infrastructure and the yield levels,has reached to 0.4701.Level 2 agricultural land has been converted to level 1 from 2006 to 2015,in Da Qin Ta La,Ming Ren,Zhi An because of effectively probability of irrigation and infrastructure supporting;The distribution of sand soil in northwest has reached 127.19Km2,41% of which is sandy soil texture,with low soil nutrients and seriously soil erosion and low yield,so that part of level 1 and level 3 agricultural land changed into level 2;Terrain and irrigation water is obviously in Yi Long Yong town and Xin Zhen town,resulting in level 2 and level 4 agricultural land turned into level 3;Part of level 3 agricultural land in the mountainous areas in Qing Long Shan and Xin Zhen town has changed into levels 4.Although facing frequently soil erosion,discontinuous agricultural land,and scattering in the gentle slope areas,and the natural weight of the terrain and soil texture has reached to 0.3926,the complete farmland infrastructure,the effectively coordination of irrigation and drainage system could improve the use of inferior agricultural land,which has more practical significance compared with natural conditions improvement. |
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