Remote sensing extraction and spatial pattern analysis of cropping patterns in black soil region of Northeast China at county level

Cropping patterns play a significant role in soil fertility and crop production in the black soil region of Northeast China. It is highly demanding for reasonable cropping patterns to make full use of black soil sources at present. However, it is still lacking in a systematic analysis related to the types and spatial distribution of cropping patterns in black soil areas. Taking Kedong County of Heilongjiang Province in China as the research area, this study aims to determine the remote sensing extraction and spatial county-level cropping patterns in the black soil region, particularly on combining with Geo-information Tupu. The specific procedure was as follows. Firstly, the extraction of crop distribution over six years was realized in ENVI software using the Landsat 8 OLI remote sensing images of six phases from 2012 to 2017. Then, the information Tupu of crop change was obtained using the space superposition function of GIS, where the crop change was classified to identify the types and areas of cropping patterns. Finally, the kernel density estimation was utilized to determine the spatial agglomeration of cropping patterns, while the spatial structure characteristics were calculated for the proportion of cropping patterns in each administrative village. The results show that: 1) The total planting area of soybean and maize exceeded 94% in Kedong County from 2012 to 2017, indicating the changing trend of "decreasing first before increasing" and "increasing first before decreasing". There were also relatively low and stable acreages and variations of rice and other crops. 2) Five cropping patterns were identified, and then sorted by the area from large to small as follows: disordered, soybean continuous, two-year crop rotation, maize continuous, and three-year crop rotation cropping pattern. Among them, the first three cropping patterns accounted for the largest sum of 83.90%. 3) The soybean continuous cropping pattern presented an obvious trend in the west and north county, while, the disordered cropping pattern was distributed in the central, east, and south county. The maize continuous cropping pattern was distributed in the northeast-southwest belt, while, the three- and two-year crop rotation pattern showed the distribution patterns of "local aggregation and global dispersion". 4) The cropping patterns at the administrative village scale were roughly divided into five types, among which "disordered cropping-soybean continuous cropping-two-year crop rotation" dominated, and widely distributed in the northwest-southeast county. Followed by "soybean continuous cropping-disordered cropping-two-year crop rotation" and "disordered cropping-maize continuous cropping - two-year crop rotation", the former was scattered in the eastern county, and the latter was distributed in the northeast-southwest belt. The administrative villages with the patterns of "disordered cropping-two-year crop rotation - soybean continuous cropping" and "disordered cropping-two-year crop rotation-maize continuous cropping" were scattered in the east and southeast county. © 2021, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.