Agricultural Production Structure Optimization: A Case Study of Major Grain Producing Areas, China

A large number of mathematical models were developed for supporting agricultural production structure optimization decisions; however, few of them can address various uncertainties existing in many factors （e.g., eco-social benefit maximization, food security, employment stability and ecosystem balance）. In this study, an interval-probabilistic agricultural production structure optimization model （IPAPSOM） is formulated for tackling uncertainty presented as discrete intervals and/or probability distribution. The developed model improves upon the existing probabilistic programming and inexact optimization approaches. The IPAPSOM considers not only food security policy constraints, but also involves rural households’income increase and eco-environmental conversation, which can effectively reflect various interrelations among different aspects in an agricultural production structure optimization system. Moreover, it can also help examine the reliability of satisfying （or risk of violating） system constraints under uncertainty. The model is applied to a real case of long-term agricultural production structure optimization in Dancheng County, which is located in Henan Province of Central China as one of the major grain producing areas. Interval solutions associated with different risk levels of constraint violation are obtained. The results are useful for generating a range of decision alternatives under various system benefit conditions, and thus helping decision makers to identify the desired agricultural production structure optimization strategy under uncertainty.

Urban Expansion in Major Grain Producing Area from 1978 to 2017:A Case Study of Zhengzhou Metropolitan Area,China

The spatial form of urbanization in China has developed from single-core city expansion to a multi-center metropolitan area.However,little attention has been paid to the growth process of the emerging metropolitan area situated in major grain producing locations in the central China.Taking the Zhengzhou metropolitan area(ZZMA)as a case study,we developed an inverse S-shape model to characterize the spatial distribution of urban land density,and constructed an urban expansion core index,urban expansion intensity index,and urban compactness index to quantify the spatial structure change that has taken place from 1978 to 2017 during the process of urban expansion.Moreover,cropland contribution rate(CR)was constructed to evaluate the impacts of urban expansion on croplands.We uncovered four key findings.First,over the past 40 yr,the ZZMA has experienced dramatic expansion,and the central city of Zhengzhou expanded faster than other cities.The gravity centers of urban expansion of surrounding cities were moving toward to Zhengzhou City.Second,the urban land density decreased with the distance from the city center to the outskirts.As the only large city,Zhengzhou has experienced the fastest and most compact centralized urban expansion,especially after 2000,while other medium-and small-sized cities have experienced low-intensity decentralized expansion.Third,the urban core has been gradually expanding outward.From 1978 to 2017,the hot-zone of urban growth has moved progressively with the acceleration of urbanization.All cities except Jiaozuo had a single peak in different periods.Forth,the cities in national core grain-producing areas has higher cropland contribution rates and lower urban expansion areas,which was closely related to cropland protection.Further analysis showed that large city was relatively better positioned than smaller cities in the efficiency of their urban infrastructure and the effectiveness of wealth creation efficiency in the urbanized area could be tested in all cities,and the policy factor seemed to play an important role in the urban expansion process.

Changes and Effecting Factors of Grain Production in China

Based on the data from the Cost-benefit Data of Farm Produce and the China Agricultural Yearbook, this paper aims to examine the spatial and temporal change characteristics of total grain production and its affecting factors. The results show that： 1） During 1980 to 2007, total grain production increased from 3.20 ~ 108 t to 5.02 x 108 t in China, with annual increasing rate of 1.68%. From the regional disparities, most of the regions present increasing trend of total grain production except for several regions with higher level of economic development; 2） Grain sown area decreased from 1.17 × 108 ha in 1980 to 1.06 x 108 ha in 2007, which has negative effect on total grain production; 3） The increase of grain yield per unit area caused by land use intensity changes contributed to the increase of total grain yield greatly. However, as the land use intensity showed that farmers pay more attention to labor-saving input but not yield-increasing input, the less enthusiasm of farmers in grain production may become an important constraint on fu- ture grain production increase in China; 4） Based on the results, this paper proposed different land management poli- cies in different regions, for example, the government should protect cultivated land, promote large scale production. As to the less developed regions, the government should pay more attention to agricultural subsidies to promote farm- ers＇ enthusiasm in grain production.

Variation Character of Grain Yield per Unit Area in Main Grain-producing Area of Northeast China

Based on the surveys and the statistic data during 1980-2003, the variation character of grain yield per unit area in Northeast China and its main factors have been discussed by the methods of statistics and grey correlation analysis. The results show that: 1) the grain yield per unit area has been taking on an increasing trend in the recent 20 years. It increased from 2519.80kg/ha in 1980 to 4216.11kg/ha in 2003, with an increasing rate of 67.32%; 2) the variation of grain yield per unit area is considerably prominent and its range is also very great, with the maximal increase rate of 42.59% and maximal decrease rate of 21.13%, respectively, which are far above the whole Chinese average level; 3) the variation of main crops' yield per unit area is remarkable, which takes on the character that the yield of corn is much higher than that of soybean and rice; and 4) the grey correlation analysis shows that the most important factors impacting the variation of grain yield per unit area are the total power of agricultural machinery, the consumption of chemical fertilizer and effective irrigated area. However, the influence of natural disaster and income level should not be ignored. Effective ways to improve grain yield per unit area are to construct farmland improvement groundwork, reclaim the middle- and low-yield farmland, etc.

Increasing Subsidies to Main Grain Production Area——Necessity of the Rejuvenation of Northeast China

As an old industrial base, Northeast China is one of the most important grain production base. To rejuvenate Northeast China, it is necessary to strengthen farming products processing, lengthen industrial chain and develop sustainable agriculture.

Performance evaluation of ecological compensation policy for cultivated land in China

The paper evaluates the changes in the ecological environment of cultivated land in the major crop-producing areas major crop-producing areas in the past 20 years by constructing an ecological pollution index;and quantitatively analyzes the effects of the existing policies and their main influencing factors by applying the PSM-DID method based on the frequency of policy enactment.The results are as follows:first,the existing ecological compensation policies for cultivated land are effective but not significant in improving the ecological environment in the major crop-producing areas.The economic development level and grain cultivation area of the major crop-producing areas are significantly and positively correlated with the improvement of the arable land ecological environment,while the level of agricultural infrastructure construction is significantly and negatively correlated with the improvement of the arable land ecological environment.Second,the reason for the ineffectiveness of the current arable ecological land compensation policy in protecting the arable land ecological environment in the main grain-producing regions is that the existing arable ecological land compensation policy in China has its own institutional defects and needs to be further improved.At the same time,the level of environmental pollution of cultivated land in the main grain-producing regions is positively correlated with the level of income from cultivated land and cultivated area.

Holistic identification and assessment of environmental risks of arable land use in two grain producing areas of China

Taking two typical grain producing areas of southern(Dongting Lake Region)and northern China(Shandong Province)as examples,this study used fault tree analysis and parametric estimation to provide a comparative analysis for environmental risks of intensive arable land use.The results show that(1)in the risks of eutrophication,toxicity,soil structure,greenhouse effect and air pollution,the greenhouse effect was the most prominent with the highest discharge;(2)the Dongting Lake Region discharged less pollutants annually than did Shandong Province,while surpassing Shandong in cumulative pollutant discharge in 2007-2018;(3)the spatial distribution of environmental risk in the Dongting Lake Region was mostly concentrated in the northern area,whereas that in Shandong Province displayed a scattered pattern;(4)in the Dongting Lake Region,Yueyang,Changde,and Yiyang were high environmental risk cities in 2007-2018,whereas in Shandong Province,Zaozhuang,Heze,Liaocheng,and Dezhou exhibited higher comprehensive environmental risk indexes in 2007-2008,while Rizhao replaced them in 2018.The results indicated that ago-production material use must be controlled,reasonable zoning for areas posing environmental risks must be employed and cities with high environmental risk must be dynamically monitored to prevent the intensification of environmental risks of arable land use.