Spatial-temporal characteristics and influencing factors of grain yield change in China

Abstract: Despite high attention to the stability and increase of grain production and market supply by Chinese government, grain yield in China has been undergoing a great fluctuation during the past decades, which could be a big challenge to national food security. This paper thus analyzes the spatial-temporal characteristics and influence factors of grain yield change in China since 1990 from the aspect of evolution stages and main types. Statistical indicators and spatial econometric models for panel data are introduced, which are supported by Geodata, ArcGIS, and Matlab software. It shows that the growing process of Chinese grain yield has three stages, namely stage 1990-1998, 1998-2003, and 2003-2011 respectively. Meanwhile, provinces in China can be categorized into three sets according to different supply-demand relationships, which are provinces with surplus grain (PGSG), provinces with balanced grain supply and demand (PBGSD), and provinces with insufficient grain supply (PIGS). The three separate types vary every year, with different provinces included each other. Roughly speaking, the grain production status of eastern provinces, central provinces, western provinces, and northeastern provinces is decreased, weakened, enhanced and strengthened respectively. In 2011, the PGSG, the PBGSD, and the PIGS distribute mainly at North, Middle, and South China respectively. Among all the factors that influence grain yield, the land factor has a significant positive impact, changing from strong to weak. It indicates grain production in China is increasingly dependent upon factors that contribute to per unit yield, such as technical progress, capital investment, etc. The labor factor brings an effect from positive significant to insignificant then negative significant, reflecting the change of agricultural surplus labor, rural labor structure, etc. The impact of different types of capital input varies as follows. Definitely, agricultural infrastructure investment, represented by irrigation facilities, has a strong positive effect. As a kind of labor saving capital investment, the total power of agricultural machinery brings about 'positive to negative and positive again' effect; the chemical fertilizer input, as a representative of agricultural materials, follows the law of diminishing returns to scale. Besides agricultural production factors, agricultural structure adjustment, non-agricultural industry development, and random error factors of neighboring provinces also influence the actual yield. As to the three separate types, the driving mechanism of grain yield change differs significantly, including the impact of agricultural production factors and that of macro environment. It is the mutual result of both internal law such as diminishing marginal returns and scale effect and external factors such as government regulation. Taking into account the above different driving mechanism, it will be meaningful to promote the regional division of grain production among the PGSG, the PBGSD, and the PIGS, to protect a large-scale arable land resource with a special priority to the project of arable land consolidation and protection in PGSG, to change the focal point of financial support and land consolidation to improve the efficiency of agricultural infrastructure, to solve the scarcity of agricultural labor by measures such as the cognizance of agricultural producers, and to promote agricultural mechanization with an emphasis to plain agricultural area, and which in all will help stabilize and increase grain yield in China.