| Food security is one of the important guarantees of national security.Under the pressure of increasing cultivated land area and grain yield per unit area,keeping or increasing cultivated land multi-cropping is the most effective and feasible way to ensure food security.Rice is one of the main grain crops with the highest cultivated land multiple planting index,and its output is about 1/3 of the total grain,which plays a pivotal role in grain production.The southern region is the core area of rice multi-cropping.However,under the background of modern rapid urbanization,the opportunity cost of rural labor keeps rising,and a large number of double-cropping rice is planted in the southern region instead of single-cropping rice.The total output of rice shows a continuous decline,and the grain production pattern of "south-to-north grain transfer" has gradually changed to "South-to-south grain transport".The continuous decline of rice multiple cropping index has obviously affected the total rice production in China and may affect the food security strategy in the end.In this paper,the main grain producing areas in southern China are taken as the research area.Firstly,the remote sensing image map of rice planting system is obtained by analyzing the existing remote sensing data.Then,the trend and pattern evolution of rice multiple cropping index are analyzed by combining the statistical data from 1990 to2020,and the grain yield loss caused by the change of double cropping rice planting is calculated.The key influencing factors and formation mechanism of inter-provincial differences are discussed in terms of macro-statistical data and micro-cost-benefit of farmers.On the basis of analyzing the inter-provincial differences in the variation trend of double-cropping rice planting,the factors affecting the proportion of double-cropping rice planting and the driving factors of the variation trend of double-cropping rice planting were investigated by using geographic detector.The main conclusions are as follows:(1)From 1990 to 2020,the proportion of double cropping rice in South China generally declined,and the planting trend shifted to south obviously.In 1990,doublecropping rice was widely distributed in all areas of the study area.Except northern Anhui Province,central and northern Hubei Province,where single-cropping rice was planted,the remaining areas were dominated by double-cropping rice.In 2020,the obvious trend of double cropping rice planting was southward,and the proportion of double cropping rice planting in the northern provinces of the study area decreased significantly.The change of double cropping rice proportion in the study area was classified into three categories:(1)rapid decline area.Including Zhejiang,Anhui and Hubei;(2)slow descent zone.Including Hunan,Jiangxi and Fujian;(3)Stable zone.Including Guangdong and Guangxi.(2)Based on the 2020 per unit yield level,the "double order replacement" in the eight provinces in the study area led to a reduction of 26.3 million tons of rice output,accounting for 26.5% of the total production in the study area in 2020,accounting for12.4% of the total rice output in 2020.Jiangxi and Hunan had the largest decrease in yield due to the proportion of double cropping rice planting.The net loss of grain in Shangrao and Yichun of Jiangxi Province was more than 1.5 million tons due to the "double change order",which was more than 10% of the net loss of the eight provinces in the study area.(3)Latitude and accumulated temperature were the core factors that caused the decrease trend of rice multiple cropping index between provinces.In general,latitude determines accumulated temperature,accumulated temperature determines labor cost during "double grab",and the difference of labor cost determines the inter-provincial difference of rice multiple cropping index.The sensitivity of the proportion of doublecropping rice to the increase of labor cost varies according to latitude.The increase of labor cost had the most significant effect on the proportion of double-cropping rice in high latitudes and the least effect on low latitudes such as Guangxi and Guangxi,which did not pass the significance test.For Zhejiang,Jiangxi and Guangxi,Zhejiang has the lowest labor supply and demand index in the season of "double grab" and is faced with serious labor shortage.Jiangxi is barely balanced and Guangxi is not at risk of labor shortage.When the three provinces choose double-cropping rice planting,the benefit of Zhejiang is far lower than that of other provinces,regardless of whether the family labor force discount is counted,and the benefit of Guangxi is the largest.(4)The core factors affecting the proportion of double cropping rice planting in 1990 were the per capita disposable income of farmers,the average salary of workers and the per capita cultivated land area.The core factors in 2020 are the effective irrigated area,the amount of agricultural fertilizer applied per mu and the area of cultivated land per capita.In 1990,the largest interaction term is the interaction between slope and total mechanical power per mu,and in 2020,the largest interaction term is the interaction between rural population and per capita GDP.The core of the detection results of the trend factor of double-cropping rice proportion change is the per capita disposable income of farmers.The increase of farmers’ income significantly reduces the proportion of doublecropping rice planting.Based on the above conclusions,some suggestions were put forward from the aspects of formulating regional differentiated policies,encouraging land circulation,strengthening the construction of agricultural land supporting facilities,deepening the reform of rice supply side,etc.,in order to stabilize and improve the double-cropping rice sown area and yield,and ensure national food security. |
PDF Full Text Request