Quantifying the hydrological impact of soil mulching across rainfall regimes and mulching layer thickness

Abstract

Covering the soil surface with mulch is a cropland management practice that can provide several benefits to the soil environment, especially in rainfed systems. Soil mulching tends to enhance plant growth by reducing soil evaporation and potentially increasing transpiration, but its effectiveness vary widely across rainfall regimes and mulching materials. Here we investigate this variability using a process-based modeling framework coupling the dynamics of soil and mulching moisture and of crop growth. Supported by field observations under different mulching materials, we study the effectiveness of soil mulching in increasing transpiration and growth under different rainfall regimes and mulching layer thickness. The analysis suggests that in most rainfall scenarios soil mulching can increase plant transpiration by up to 100% and reduce soil evaporation by up to 40%. However, there exist rainfall conditions (low frequency and high intensity) under which soil mulching may cause lower transpiration. We also show that soil mulching is particularly beneficial during a dry spell, a phenomenon that is projected to occur more frequently in many climatic zones. In the event of a dry spell during the growing season, soil mulching helps maintain moist conditions for longer, hence limiting the negative effects on plant transpiration and growth. The analysis helps better understand the role of soil mulching on transpiration and crop growth and provides important information for improving soil mulching depending on mulching material and the site-specific rainfall regime.