Evaluation of agricultural land suitability for soybean cultivation in the Sanjiang Plain, Northeast China

The Sanjiang Plain is one of the most important grain production base in China. The importance of the plain could increase with the promulgation of policies that encourage farmers to cultivate soybean to adapt to the global climate change and CO₂ concentration rise. In order to make full use of the advantages in climate and soil conditions, there is the need for rational allocation of soybean cultivation areas in the Sanjiang Plain. In this paper, firstly, we carried out climate suitability evaluation for the cultivation of soybean based on climate and soil inventory with the GAEZ framework of FAO/IIASA. Then, we used soil thickness, soil texture, soil pH, land drainage and flooding conditions as indicators of soil suitability evaluation and the results of the analysis were degraded by Albic bleach soil in the Sanjiang Plain. Finally, the results of the agricultural land suitability evaluation were obtained by overlapping layers in GIS at the grid scale (30 m×30 m) and Suitability Index (S_I) calculated to geospatially compare soybean cultivation in the study area. The results showed that:1) most parts of the Sanjiang Plain was suitable for soybean cultivation, except for areas with slope≥30%.2) About 8.5×10⁴ km² (78.75% of the plain) was suitable for soybean cultivation, especially gentle slope (2%-5%) and undulating slope (5%-8%) areas along the bank of Songhua, Woken and Muleng Rivers with good soil texture and high drainage. 3) Nine counties with the highest S_I (≥70%) included Boli, Yilan, Tangyuan, Jamusi, Jixian, Huachuan, Youyi, Suibin and Fujin. Then 10 counties (Tongjiang, Huanan, Hulin, Baoqing, Fuyuan, Qitaihe, Luobei, Jidong, Raohe and Shuangyashan) had higher S_I (60%-70%); Hegang, Mishan, Jixi and Muleng counties had the lowest S_I (S_I≤60%). 4) For its simple and objective evaluation procedure, the GAEZ framework was applicable in locally distinguishing spatial differences in soybean cultivation areas needed in rational land allocation.