Approaches to model the impact of tillage implements on soil physical and nutrient properties in different agro-ecosystem models

Tillage is a primary field operation aiming to modify the soil structure to favour agronomic and soil related processes such as soil seed contact, root proliferation, water infiltration, incorporation of residues, break down of soil organic matter and land forming. The modification of the soil physical and chemical properties especially in the upper soil layers after a tillage operation can be huge. The application of field-scale crop growth models is a widely accepted tool for process understanding but also to support an efficient and sustainable crop production. Agro-ecosystem models are composed of different sub-modules for certain processes related to crop growth and soil-nutrient and water dynamics in response to atmospheric conditions. In this study, the approaches to simulate the impact of tillage on soil physical properties and on vertical distribution of organic matter and nutrients implemented in 16 different agro-ecosystem models (APEX, APSIM, CropSyst, DAISY, DayCent, DNDC, DSSAT, EPIC, HERMES, HYDRUS-1D, LPJmL, MONICA, SALUS, SPACSYS, STICS, and SWAT) are reviewed. Some of the reviewed agro-ecosystem models simulate the tillage effects on soil bulk density, soil settlement, soil texture redistribution, and several soil hydraulic properties. To some extent, the changes in soil porosity, soil aggregates, and the soil organic matter content are considered. Most models simulate the incorporation or/and redistribution of organic matter, residues or/and nutrients in the soil. None of the models consider the changes in biochemical properties such as changes in soil microbial biomass and activity or redistribution of weed seeds after a tillage operation. This study indicates the urgent need to improve the tillage components in crop modelling due to its obvious impact on various soil and nutrient processes and consequently, on crop growth and yield.