# Exploring a Moderate Fallow Scale of Cultivated Land in China from the Perspective of Food Security
## 1 Introduction  
The grain output of China has increased for 12 consecutive years since 2004, and the grain production capacity has greatly improved [1]. However, the ecological environment has paid a large price, such as in the thinning of the black soil layer [2; 3], soil erosion [4], soil acidification [5; 6], excessive heavy metals in soil [7], and increased non-point source pollution [8; 9]. Meanwhile, construction land continues to expand, and the corresponding cultivated land area decreases yearly with the rapid development of urbanization [10; 11; 12]. The quality and quantity of cultivated land in China are declining to varying degrees, and great challenges exist for increasing the grain supply under the dual pressures of increasing pollution in agriculture and future construction land expansion [11; 13]. To solve ecological environmental problems such as land degradation, the Chinese government issued a pilot programme for exploring and implementing cultivated land rotation and fallow systems in 2016 [14; 15]. Subsequently, Central Committee No.1 documents have been proposed for three consecutive years to further expand the pilot scale of cultivated land rotation and fallow systems. China has implemented cultivated land rotation and fallow pilot programmes in groundwater funnel areas, heavy metal contaminated areas, and degraded ecological environmental areas [15; 16], and since that time, the fallow scale has continuously expanded, from \(41\times 10^{4}\) hm\({}^{2}\) in the initial stage to \(80\times 10^{4}\) hm\({}^{2}\) in 2017. In 2019, the pilot rotation and fallow scales supported by the central government were further expanded to \(200\times 10^{4}\) hm\({}^{2}\), in which the fallow area was \(34\times 10^{4}\) hm\({}^{2}\). The fallow system has yet to be implemented throughout the country, although pilot programmes have been implemented in 15 provinces, such as Inner Mongolia, Liaoning, Jilin, and Heilongjiang. However, food security has always been a focus of national concern [17]. Considering the large population and scarce land resources in China, determining a reasonable fallow scale of cultivated land under the premise of ensuring food security is a key issue that needs to be solved immediately. Regarding the abovementioned issue, some scholars have explored the fallow scale of cultivated land from the perspective of food security, but there are large differences in the understanding of fallow scale [18; 19]. Some studies reported that the total fallow scale of cultivated land in China should be controlled within 5% to 8%, with a maximum proportion not exceeding 20% [18; 19]. [PERSON] et al. discussed the theoretical fallow scale in China on the basis of the prioritization of food security and suggested that the appropriate fallow scale was \(400\times 10^{4}\) hm\({}^{2}\)[17]. Moreover, [PERSON] and [PERSON] determined a base planting area of \(1.08\times 10^{8}\) hm\({}^{2}\); the authors believed that the proportion of fallow land should be controlled at 6-8% and that the fallow scale limit in China should be \(2730\times 10^{4}\) hm\({}^{2}\)[20]. Thus, the difference in the fallow scale estimated by the two abovementioned papers is 6.83 times. However, the previously mentioned studies had some limitations, mainly concerning the fallow scale of cultivated land [17; 18; 21]. First, most of the studies focused on theoretical analyses and lacked accurate data for systematic calculations, making it impossible to make scientific judgements regarding the current fallow scale. Second, existing studies used the minimum per capita cultivated land area or the population carrying capacity of land as the basis to statistically estimate the fallow area and did not consider land use change. With the development of the social economy and urbanization, many labourers have moved from rural areas to cities in the past 30 years in China [22].