Effects of spatiotemporal variations in visible and invisible non-grain production cultivated land on grain yield in the Guanzhong Region of Shaanxi in China

Non-grain production of cultivated land has a serious impact on grain production and national food security. Taking as a research area, this study aims to clarify the temporal and spatial changes of visible non-grain production of cultivated land (VNGPCL), and invisible non-grain production of cultivated land (INGPCL). The land use, vegetation index, and socio-economic data were also collected in 2000, 2010, and 2020. A systematic investigation was then implemented to determine the effects of VNGPCL and INGPCL on the grain yield. The results show that the degree of VNGPCL was ever-intensifying, where the areas were 131276.93 and 744755.60 hm² in 2000-2010 and 2010-2020, respectively. There was a 5.19% proportion of VNGPCL area in 2000-2010 to total cultivated land area in 2010. By contrast, there was a 29.10% proportion of VNGPCL area in 2010-2020 to total cultivated land area in 2020. The area of VNGPCL from 2010 to 2020 was 5.61 times that of from 2000 to 2010. The VNGPCL was transformed mainly into grass land, urban and rural construction land, forest and garden land. There was also the ever-increasing area and proportion of INGPCL each year. The areas of INGPCL were 1306663.34, 1409341.58, 1608487.67 hm² in 2000, 2010, and 2020, respectively. The proportions of INGPCL area to the total cultivated land area in 2000, 2010 and 2020 were 51.69%, 55.07% and 66.69%, respectively. There was a significant spatial auto-correlation in the VNGPCL and INGPCL from 2000 to 2020, indicating the increasing spatial agglomeration. An increasing trend was found in the grain lost caused by VNGPCL and the proportion to grain yield. The average amount of grain lost caused by VNGPCL accounted for 0.10 and 0.74 of the grain yield in 2010, and 2020, respectively. The grain lost caused by INGPCL was greater than that by VNGPCL in 2000, 2010, and 2020. An overall increasing trend was found in the proportion of grain lost caused by INGPCL to grain yield from 2000 to 2020. The average grain lost caused by INGPCL to the grain output was 1.37, 1.16 and 1.95 in 2000, 2010, and 2020, respectively. The grain lost caused by INGPCL was much greater than that by VNGPCL. Therefore, the INGPCL can be attributed to low grain cultivation. It is an important way to reduce the INGPCL for higher grain yield and grain security. Effective measures are also urgent to manage and formulate the INGPCL for better grain production.