Effect of cover crop management on soil hydraulic properties

Cover crops are important for improving soil quality. They can provide multiple soil, agricultural and environmental benefits. The objective of the study was to compare the effects of cover crop management on soil hydraulic properties which included saturated hydraulic conductivity (Ksat), soil water retention, bulk density, and pore-size distributions over time. The experiment was carried out on a Grundy silt loam (fine, smectitic, mesic Aquertic Argiudolls) at the Chariton Country Soil Health Farm, Missouri, USA The main grain crops were a corn (Zea mays L.)/soybean (Glycine max L.) rotation. Cover crops included radish (Raphanus sativus L var. longipinnatus), cereal rye (Secale cereals L), cowpeas (Vigna unguiculata), buckwheat (Fagopyrum esculentum), barley (Hordeum vulgare L), red clover (Trifolium pretense), turnips (Brassica rapa L), hairy vetch (Vicia villosa Roth.), triticale (Triticale hexaploide Lart.), and winter peas (Lathryrus hirsutus L.). Undisturbed soil cores, 7.62 (diam.) by 7.62 (L) cm, were collected 1, 2 and 5 years after cover crops were established from six replicate locations by 10-cm depth increments from the surface to the 40-cm depth. Results illustrated that cover crop management significantly affected Ksat by year. The highest Ksat values (64.6%) were observed 5 years after cover crop establisment compared to first and second year soil samples. However, bulk density, soil water retention and pore-size distributions were affected significantly by soil depths. Soil bulk density values were significantly lower at the soil surface 0-10 cm depth. Macropores, coarse and fine mesopores, and Ksat values were significantly higher at the 0-10 cm and 10-20 cm depths compared to deeper soil depth. Soil water content was higher at the 30-40 cm depth for all soil water pressures due to higher clay content. Significantly higher water retention was determined 5 years after cover crop establishment for the -2.5 kPa soil water pressure. This study demonstrated that cover crops slightly improve some hydraulic properties in claypan soils but the changes may take several years.