The Effect of Mulch Type and Thickness on the Soil Surface Evaporation Rate

There is a continual drive to conserve water and improve irrigation efficiency in agriculture, especially in regions where water resources are limited and regulated. Mulching is one cultural practice which can be used to reduce water needs. Using certain agricultural byproducts as mulch is a sustainable practice which can provide other benefits as well such as improving soil. Wheat straw, grass clippings, and leaf debris are fairly abundant byproducts which can be used as mulch. An experiment was conducted to determine which of these readily available mulching materials would be best at conserving soil moisture, and at which thicknesses, 5, 10, and 15 cm. Soil water content was monitored every three days for a duration of three weeks, when no discernable differences were measured. Within the first 3 days, a mulch layer of at least 5 cm reduced surface evaporation to 40% compared to the water losses from bare soil, and all mulch types were equally effective. While there were no differences between the mulch types, the mulching rate did have a significant effect on water loss. Doubling the mulching rate from 5cm to 10 cm maintained soil moisture 10% higher throughout most of the experiment. However, increasing the rate further to 15 cm had no discernible effect. This experiment clearly demonstrates that what might otherwise be agricultural waste can be used to significantly conserve soil moisture, providing more resources for crops and reducing overall costs of production.