Research On The Spatial Allocation Of Cultivated Land Fallow In Serious Ecologically-degraded Area

Upgrading the cultivated land rotation and fallow to a system is China's long-term strategy of"food crop production strategy based on farmland management and technological application".On the one hand,China's long-term emphasis on the concept of“storing grain in the warehouse”for food security has led to such problems of agricultural supply-side as overproduction of grain for a period of time.On the other hand,in recent years,China's cultivated land has been over-utilized,resulting in a decline in cultivated land productivity,ecological problems such as soil degradation,groundwater overexploitation and heavy metal pollution,thus severely restricting the sustainable development of China's agriculture and social economy.In June 2016,the"Explore the Pilot Program for Implementing the System of Cultivated Land Rotation and Fallow"took the initiative to carry out the pilot study of fallow in groundwater funnel areas,heavy metal pollution areas,and serious ecologically-degraded areas.At present,China has basically formed a work mechanism of“fallow being coordinated by our central government,managed by provinces,and implemented by each county”.However,as China's cultivated land fallow system is still in the pilot exploration stage,and foreign countries'fallow system practices are limited in practice.In the process,fallow efficiency and benefits may be damaged due to misallocation of the fallow cultivated land.At present,the problem of the fallow spatial allocation in China's fallow system pilots is mainly concentrated in severe ecological degradation areas,such as“the result of fallow area selection is contrary to the objectives of the fallow system,the mismatch of fallow areas and the loss of fallow benefits”,“the lack of scientific screening of fallow land in pilot areas according to the standard,in areas with severely fragmented cultivated land,it is difficult to cover the fallow inferior land with concentrated contiguous fallow."Compared with groundwater over-exploitation areas,severely degraded ecology areas in the northwest and heavy metal pollution areas,the rocky desertification area in Southwest China has more people and less land,the contradiction between human and land is more prominent,and the research on the fallow spatial allocation of is more complicated.This paper is based on exploring the basic theory and technical method system of fallow spatial allocation,in order to solve the problem of fallow inefficiency and profit loss caused by the mismatch of fallow land in severely ecologically-degraded areas.On the basis of combing and summarizing relevant literature data,the paper systematically explained the basic problem domain and basic principles of fallow spatial allocation,and formed the theoretical analysis framework of fallow spatial allocation.Songtao County in Guizhou Province,a severely degraded area and the first batch of fallow pilot counties in the China,was selected as the case to discuss in depth the process of fallow spatial allocation at the county scale:firstly,apply the cultivated land emergy method and the ecological footprint method to calculate the range of fallow area to form a scale basis for the fallow region arrangement;secondly,based on fallow goal,for different types of the cultivated land(paddy and dry land),adopt the comprehensive evaluation method of the cultivated land health and the spatial constraint method to carry out the spatial arrangement of the fallow regions;finally,multiple fallow technical modes and their corresponding suitable fallow crops are arranged reasonably in fallow regions.The main conclusions are as follows:(1)It systematically explained the basic problem domain and the basic principles of spatial allocation of the cultivated land fallow,formed a theoretical analysis framework of fallow spatial allocation,and provided a theoretical guidance for the empirical research on spatial allocation of the cultivated land fallow in different spatial scales and different region types.The connotation of spatial allocation of the cultivated land fallow in a broad sense is to optimize the combination of the fallow scale,the fallow region,the fallow time sequence,and the fallow technical mode,in order to realize the macro-control of“quantification,positioning,sequencing,and determining technology”of the cultivated land fallow,including 3 core research contents:fallow scale calculation,spatial arrangement of the fallow regions and spatial arrangement of the fallow technical modes.Two key issues that need to be solved urgently for spatial allocation of the cultivated land fallow in China are the spatial arrangement of the fallow regions at different scales and the spatial arrangement of the fallow technical models in different areas.The difficulties and focus of solving these two key issues are building a comprehensive model or evaluation index system and dividing evaluation standards.At present,there are mainly 4 types of spatial allocation of the cultivated land fallow:goal-oriented spatial allocation,execution method-oriented spatial allocation,multi-condition constraint-oriented spatial allocation and technology-oriented spatial allocation.The fallow spatial allocation is composed of a three-level system of"country-region(including region,province and city)-county"and five procedures of"goal determination?object recognition?scale calculation?regional arrangement?technical mode arrangement".(2)The ecological profit and loss of the cultivated land productivity can be used as a criterion for determining whether a township should be lay fallow by calculating the maximum value of fallow cultivated land area,especially for calculation of ecologically cultivated land area.Because ecological deficit of the cultivated land productivity in Songtao County has been determined by calculating ecological profit and loss of the cultivated land productivity,the cultivated land should be lay fallow totally:the average ecological carrying capacity of the cultivated land is121842.57hm²,0.17 hm²per capita,and the average ecological footprint of the cultivated land is165408.49hm²,0.23 hm²per capita.What's more,there are 25 townships in Songtao County,which should be lay fallow except for 3 townships.According to the statistic of county's average level(SCAL)and the statistic township level(STL),the largest fallow area is 19558.62 hm²and17673.83 hm²,respectively.Townships with the largest fallow area of more than medium grade are scattered in 8 townships in 4 regions:Huangban Town,Yajia Town and Shichang Street in the northeast region;Mengxi Town in the middle region;Ganlong Town in the west region;Panxin Town,Niulang Town and Daxing Street in the southeast region.(3)The emergy sustainability index of the cultivated land(ESI_cl)can be used as the criterion for determining the sequence of the fallow townships,that is to say,the sum of the maximum fallow area of the priority fallow townships are the minimum fallow area.Songtao County's ESI_clis low and should be moderately lay fallow.There are 2 townships with priority fallow(Yajia Town and Taipingying Street),23 townships with moderate fallow(Liaogao Street,Huangban Town,Ganlong Town,etc.),and 3 townships with no fallow(Shichang Street,Niu Lang Township and Yong'an Township).The minimum fallow area in the county is 1396.10 hm²,accounting for 1.88%of the total cultivated area.According to the statistics of county's average level(SCAL),the range of fallow area in the county is 1396.10hm²?19558.62hm²,accounting for 1.88%?26.34%of the total cultivated land area;according to the statistics of township level(STL),the range of fallow area in the county is 1396.10hm²?17673.83hm²,accounting for 1.88%?23.8%of the total cultivated land area.(4)The important basis of the spatial arrangement of fallow regions is the diagnosis and identification of fallow cultivated land based on the comprehensive evaluation of cultivated land health,which is determined by the quality goal and productivity goal of the cultivated land.In severe ecologically-degraded area,the first-level indicators of the cultivated land quality goal include soil condition and cultivation condition,and the first-level indicators of the cultivated land productivity goal include climatic condition,natural quality,and technical level.Whereas the second-level indicators depend on the different cultivated land types,which need to be selected reasonably based on the actual situation of the region and fallow requirements.Songtao County's cultivated land quality is better and the cultivated land productivity is ordinary,the area of cultivated land with ordinary high quality and ordinary productivity is relatively large,the quality and productivity of paddy fields are better than dry fields,so the fallow priority should be given to the dry land with ordinary quality and low ordinary productivity.The cultivated land health is ordinary in Songtao County,the paddy fields health is significantly better than that of dry fields,so the fallow priority should be given to the dry land with low ordinary health,and the townships should be fallow mainly concentrated on 13 townships in 4 regions:Daxing Street,Panshi Town,Panxin Town,Changxingbao Town,Zhengda Town and Huangban Town in the east region,which are distributed in a strip pattern;Liaogao Street,Pujue Town,Niulang Town and Pingtou Town in the middle region;Ganlong Town and Waxi Township in the west region;Niulang Town in the south region.(5)The core content of the spatial arrangement of the fallow region is spatial constraint,with the maximum fallow area and concentrated contiguous areas as the main constraints.The fallow area in Songtao County is 7921.86hm²,which accounts for 10.67%of the county's cultivated land;the priority fallow area and moderate fallow area account for 30.3%and 69.7%of the fallow area respectively;the paddy field fallow area and dry land fallow area account for 14.56%and 85.44%of the fallow area,respectively.There are 3 townships with priority fallow and 9 townships with moderate fallow,and there are 2 townships with priority fallow for paddy fields and 3 townships with priority fallow for dry land.The non-fallow towns are Wuluo Town,Panshi Town,and Lengshuixi Town;there are 5 priority fallow townships are Yajia Town,Taipingying Street,Panxin Town,Huangban Town and Pujue Town;there are 9 moderate fallow townships,including Liaogao Street,Daxing Street,Dapingchang Town,Yajia Town,etc;Shichang Sub-district,Niulang Town and Yong'an Township are allowed temporary non-fallow;other townships can be allowed moderate fallow.Daxing Street and Niulang Town are entitled to priority fallow for paddy field;Panxin Town,Ganlong Town and Huangban Town are entitled to priority fallow for dry land.(6)The analysis of the applicability of the regional basic fallow technical model and its fallow crops is an important prerequisite for spatial arrangement of the fallow technical model,the different cultivated land types,the different fallow time sequences,and the different regions of fallow technical models have certain spatial differences.The fallow technical models in Songtao County include 4 basic fallow technical models and 3 compound fallow technical models.According to different fallow technical models,the corresponding suitable fallow crops are selected.Basic fallow technical modes include deep tillage mode,fertilization mode,texture improvement mode and comprehensive improvement mode.Compound fallow technical modes include deep tillage mode+fertilization mode,deep tillage mode+texture improvement mode,and fertilization mode+texture improvement mode.Basic fallow technical mode and its corresponding suitable fallow crops:deep tillage mode,planting rape-peanut is the best;fertilizer mode,planting rape,soybean,peanut and alfalfa;texture improvement mode,planting soybean and peanut;comprehensive improved model can be used to grow rape,soybean,peanut and alfalfa.The fallow technical model for the dry land is mainly comprehensive improvement model,suitable for planting rape,soybean,peanut and alfalfa;the fallow technical model for the paddy field is mainly deep tillage mode+texture improvement model,suitable for planting rape,soybean and peanuts.The fallow technology models of priority fallow and moderate fallow are mainly comprehensive improvement models,which are suitable for planting rape,soybean,peanut,and alfalfa.The fallow technical modes of each township are mainly comprehensive improvement mode,supplemented by deep tillage mode+texture improvement mode;the eastern townships are mainly deep plowing mode,deep tillage mode+texture improvement mode,fertilization mode+texture improvement mode,and comprehensive improvement mode;the middle and western townships are mainly fertilization mode and texture improvement mode;western townships are mainly deep tillage mode+fertilization mode.This paper has made three innovations:(1)It systematically explained basic problem domain and basic principles of fallow spatial allocation,and deconstructed the logical relationship of fallow spatial allocation academically.(2)It modified the cultivated land emergy ecological footprint improvement model(referred to as the"modified model")and cultivated land productivity sustainability index(ESI_cl),which provides a more scientific technical method for measuring the scale of regional fallow.(3)It constructed a comprehensive evaluation and analysis framework for cultivated land health,which provides a more reasonable technical method for diagnosing and identifying fallow land in different cultivated land types(paddy field and dry land).