A Comparison of Using Dominant Soil and Weighted Average of the Component Soils in Determining Global Crop Growth Suitability

Abstract

Soil parameters represent key data input for crop suitability analysis. Soil databases are complex offering soil mapping units made up of various component soils. In the case of the Harmonized World Soil Database there can be up to 8 component soils per unit. In roughly 1/3 of soil mapping units, the additional component soils take up more than 50% of the pixel share value. The soil parameter value estimate, such as pH, salinity and organic carbon content, may differ between the value of the dominant soil component and the weighted average of the values of all component soil. Understanding the effect of these differences on crop model outputs may allow quantifying the error. In this study, we show the changes in crop suitability of 15 crops while using the parameter value estimates of the dominant soils versus a weighted average of the component soils. In the case of the latter, global crop suitability amounts to 54.5% of the earth's land surface-1% more than when using the values of just dominant soils. Intrinsic regional differences in the quality of the soil database influence the distribution of crop suitability classes especially in areas where share values of the dominant soil are low. The uncertainty range for the use of dominant versus component soils on the overall global crop suitability could be considered to be 1%, while that of each suitability class can amount to up to 4%.

Global Agricultural Land Resources – A High Resolution Suitability Evaluation and Its Perspectives until 2100 under Climate Change Conditions

“…The minimum of the eight values represents the value of the soil suitability. Soil information was taken from the Harmonized World Soil Database (HWSD) [41] , considering the topsoil (0–30 cm) of the dominant and all (up to 8) component soils at a spatial resolution of 30 arc seconds [42] . Within the calculation of soil suitability, fuzzy values of each of the component soils are calculated and weighted according to their share.…”