This Is AuburnElectronic Theses and Dissertations

Cover Crop Effects on Soil Hydrology




Bonilla, Rodolfo

Type of Degree

Master's Thesis


Crop Soils and Environmental Sciences


Cover crops are known for their positive and significant effects on soils. They contribute to growing subsequent crops, reducing soil erosion, increasing water infiltration, and improving nutrient management. Cover crops can affect physical soil properties, such as infiltration, runoff, and water retention. These properties are influenced by soil structure, texture, soil organic matter, soil cover, soil water content, depth to the water table, and landscape features. The goal of this study was to determine the effect of three different cover crops, cereal rye (Secale cereale), crimson clover (Trifolium incarnatum), and radish (Raphanus sativus), on soil hydrology of Alabama soils. The objectives were to measure the saturated and unsaturated hydraulic conductivity at the soil surface and to determine the yield effects of cover crops on corn (Zea mays) and soybeans (Glycine max L.). A significant difference was found between seasons (spring and summer) and the hydraulic conductivity in the treatments (P < 0.05) for soybeans with saturated hydraulic conductivity. However, differences were not significant between seasons and the hydraulic conductivity for corn with saturated hydraulic conductivity. Also, a significant difference was found between seasons in soybean and corn (P < 0.001) for the unsaturated hydraulic conductivity in the treatments with the tension infiltrometer. There was no significant hydraulic conductivity and sorptivity difference between the crops using the ring infiltrometer method. The effects of cash crops on hydraulic conductivity appear to be stronger than the effects of cover crops during the growing season due to the root systems of the cash crops. ANOVA results showed that soybean yields were significantly higher for cover crop plots in 2020 (P < 0.001). For corn in 2020 and 2021, as well as for soybeans in 2021, there were no significant effects of cover crops on yield. The second objective of this study was to estimate the soil hydrological properties with the BEST-2K method. This method utilizes saturated and unsaturated infiltration measurements together with the soil particle size distribution to estimate the soil water retention curve and the ii hydraulic conductivity. Field experiments were conducted at two locations, the Old Rotation and a forest, on the Auburn University campus. Estimates from the BEST-2K method were compared to data measured with the HYPROP instrument. The HYPROP is used to measure the water retention curve and the unsaturated hydraulic conductivity of the soil. The BEST-2K method overestimated the volumetric water content of the water retention curve and the hydraulic conductivity for all samples. The root means square error (RSME) of the BEST-2K estimates and the HYPROP data were similar to the RSME of HYPROP field replicates. The BEST-2K method is helpful to estimate soil hydraulic properties when HYPROP instruments are not available.