IMPACTS OF COVER CROPS ON SOIL PHYSICAL PROPERTIES: FIELD CAPACITY, PERMANENT WILTING POINT, SOIL-WATER HOLDING CAPACITY, BULK DENSITY, HYDRAULIC CONDUCTIVITY, AND INFILTRATION

Field experiments were carried out to quantify the effects of cover cropping on soil physical properties. Field capacity (FC), permanent wilting point (PWP), soil-water holding capacity (SWHC), bulk density (rho(b)), saturated and unsaturated hydraulic conductivity (K-s and K-us, respectively), and infiltration rates were measured and compared for four land cover treatments [cover crop without seed maize (CC), seed maize followed by cover crop (SCCC), bare soil, and seed maize without cover crop (SC)] in three large-scale production fields (similar to 64 ha each) with silt loam soil in the 2012-2013, 2013-2014, 2014-2015, and 2015-2016 cover crop growing seasons. All production fields had been in a maize or soybean and cover crop rotation since 2002 and were farmed with row crops for decades before 2002. Field-measured soil properties in the SCCC treatment were also compared with historical values measured by the USDA-NRCS in 1974. In general, soil physical properties were unaffected by incorporating rotational cover crops into row crop cultivation. No significant differences (p > 0.05) in SWHC were observed between the treatments at any of the periods (seasons). When compared to the 1974 NRCS-measured values for the research fields, overall, the FC, PWP, and as a result the SWHC did not exhibit change at the end of the research in 2016 after cultivating cover crops since 2002. K-s values at the topsoil exhibited interannual variation for the same treatments, but there were no significant differences (p > 0.05) in K-s between land cover treatments neither in any year nor for the same treatment between years. K-us values were not significantly different (p > 0.05) between treatments neither for a given year nor between years. On average, the infiltration rate in the SCCC treatment was about 64% lower than in the SC treatment, indicating that incorporating cover crops into a maize-soybean rotation decreased the infiltration rate. While cover crops could be beneficial for grazing due to their nutritional value, and perhaps other benefits, which depend on numerous factors, in this research there was no sufficient evidence that cover crops can significantly alter the soil physical properties that were investigated in these experimental conditions.