A Case Study in Desertified Area: Soybean Growth Responses to Soil Structure and Biochar Addition Integrating Ridge Regression Models

Desertified land covers one-fourth of the world's total land area. Meeting the high food demands in areas affected by desertification is a major problem. This case study provided fundamental information to demonstrate the potential for utilizing the desertified land. The soybean trial was established in two sandy clay loam soils (desertified land) and one silty clay loam soil. Two types of biochar were applied as treatments. We aimed to investigate the response of soybean plants to soil structure, soil nutrient condition, and biochar amendment in the two types of soil. In addition, ridge regression was employed to model the plant growth indicators by soil structure, soil nutrients condition, soil water content, and biochar amendment. We conclude that (1) overall soil productivity in sandy clay loam soil is lower than in silty clay loam soil. The sandy clay loam soil may have high efficacy for crop production due to its higher harvest index. (2) Aggregate size 0.5-1 mm, 1-2 mm, and 2-3 mm indicated more important in plant biomass formation in silty clay loam soil. The low aggregate stability of sandy clay loam soil made the field more vulnerable to wind erosion in the semi-arid monsoon climate. (3) Cob biochar and wood biochar increased soybean shoot biomass by 48.7% and 45.0% in silty clay loam soil. (4) The higher N-fixing ability of nodules in sandy clay loam soil indicates an advantage to reduce the use of N-fertilizers in desertified areas. (5) Exponential polynomial regression ameliorated the accuracy of prediction of plant growth indicators in comparison to linear regression.