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Cover cropping, tillage and crop rotation management can influence soil nutrient availability and crop yield through changes in soil physical, chemical and biological processes. The objective of this study was to evaluate the influence of three years of cover crop, tillage, and crop rotation on selected soil nutrients. Twenty-four plots each of corn (Zea mays) and soybean (Glycine max) were established on a 4.05 ha field and arranged in a three-factor factorial design. The three factors (treatments) were two methods of tillage (no-tillage (NT) vs. moldboard plow [conventional] tillage (CT)), two types of cover crop (no cover crop (NC) vs. cover crop (CC)) and four typess of rotation (continuous corn, continuous soybean, corn/soybean and soybean/corn). Soil samples were taken each year at four different depths in each plot; 0–10 cm, 10–20 cm, 20–40 cm and 40–60 cm, and analyzed for soil nutrients: calcium (Ca), magnesium (Mg), nitrogen (NO3 and NH4), potassium (K), phosphorus (P), sulfur (S), sodium (Na), iron (Fe), manganese (Mn) and copper (Cu). The results in the first year showed that CT increased NO3-N availability by 40% compared with NT. In the second year, NH4-N was 8% lower under CC compared with NC management. In the third year, P was 12% greater under CC management compared with NC management. Thus, CC can enhance crop production systems by increasing P availability and scavenging excess NH4-N from the soil, but longer-term studies are needed to evaluate long-term effects. [ABSTRACT FROM AUTHOR]

Cover crops have been known to reduce soil erosion, among other benefits, and increase water infiltration, organic matter and soil microbial activity. This study was conducted at Lincoln University's Freeman farm during 2011 and 2012 to assess the effects of cover crop management on soil physical and biological properties. The soil of the experimental site was a Waldron silt loam soil (Fine, smectitic, calcareous, mesic Aeric Fluvaquents). The field was 4.05 ha in size and subdivided into 48 plots, each measuring 12.2 m x 21.3 m. The cropping pattern for the plots was a corn ( Zea mays L.)/soybean ( Glycine max ) rotation. The cover crop of choice was cereal rye ( Secale cereale ). Half of the total plots had cover crop management while the other half had no-cover crop. Soil samples were collected at four depths; 0-10, 10-20, 20-40 and 40-60 cm. Samples were oven dried at 105 o C for 72 h for soil physical properties analysis. Air dried soil samples were also sent to a commercial laboratory for analysis of soil biological properties. Results showed a significant effect (p< 0.05) of cover crop on the selected soil physical and biological properties. A 3.5% decrease was also observed in soil bulk density in cover crop plots as compared with no-cover crop plots. The carbon to nitrogen (C/N) ratio decreased with increasing sampling depth for the first three depths and increased slightly in the fourth depth (p<0.05). C/N ratio also showed a 5.6% increase in no-cover crop plots as compared with cover crop plots. The cover crop used in this study was capable of significantly improving soil physical and biological properties. [ABSTRACT FROM AUTHOR]

Perennial systems, such as switchgrass have been shown to improve soil hydraulic properties on degraded soils relative to annual cropping systems; however, studies of the effects on thermal properties are limited. Therefore, the objectives of this study were to determine the effects of topsoil thickness on soil thermal properties under switchgrass (Panicum virgatum L.) and row crop production systems. The experiment was carried out at the University of Missouri South Farm Research Center (38°54′ N, 92°16′ W). Research plots were re-established in 2009 with selected topsoil thickness categorized into two treatments (shallow [4 cm] and deep [36 cm]) on a Mexico silt loam (Vertic Epiaqualfs). Plots were planted to either switchgrass or a corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation with four replicates. Undisturbed soil cores (7.6 by 7.6 cm) and bulk soil were collected from two depths (10 cm increments) to determine thermal properties. Thermal conductivity (λ), volumetric heat capacity (C v), and thermal diffusivity (D) were measured at 0, −33, −100 and − 300 kPa soil water pressures. In addition, soil organic carbon (SOC), bulk density (D b) and water content (θ) were also determined. The results showed that the switchgrass treatment had 23% higher SOC, 5–8% greater θ, and 11% lower D b than the row crop treatment. In turn, switchgrass plot exhibited a 5–7% reduction in λ, an 8–9% reduction in D, and a 2–3% increase in C v. Shallow topsoil thickness demonstrated increased thermal properties (λ, D and C v) relative to the deep topsoil thickness, likely due to higher clay content in the surface soil horizon and associated higher θ. This study contributes to a better understanding of the impact of topsoil loss and perennial vegetation on the thermal properties of soils in degraded landscapes. • Switchgrass reduced soil thermal conductivity but increased heat capacity. • Switchgrass has the potential to buffer heat transport within the soil profile. • Management that influences bulk density also affects soil thermal conductivity. [ABSTRACT FROM AUTHOR]

Understanding the effects of cropping practices on soil pore characteristics is important for determining soil productivity and ecosystem services. Objectives of the study were to compare differences in computed tomography (CT) measured soil pore parameters (number of macropores, macroporosity, area of the largest pore, circularity and fractal dimension) among cover crops (CC), no-cover crops (NCC), and biofuel crops [Miscanthus (M): Miscanthus x giganteus and switchgrass (SG): Panicum virgatum ] and examine relationships between CT-measured pore parameters and soil hydraulic and thermal properties. Cover crops were Cereal rye ( Secale cereale L.), Hairy vetch ( Vicia villosa ) and Austrian winter pea ( Pisum sativum subsp. arvense ). Three replicates each of undisturbed soil cores were collected at two soil depths (0–10 and 10–20 cm) from each treatment using plexiglass cores measuring 76.2 mm diameter by 76.2 mm long. Ten scan images from each core were acquired using an X-ray CT scanner with 0.19 by 0.19 mm pixel resolution with 0.5 mm slice thickness and analyzed with Image - J . Soil under CC, NCC, M, and SG on average had 21, 14, 17, and 12 macropores on a 2500 mm 2 area across all the depths. Soil under miscanthus had significantly greater macroporosity (0.049 m 2 m − 2 ) and area for the largest pore (89.70 mm 2 ) than other treatments. The cover crop treatment had approximately 50%, 28%, and 75% greater number of macropores than NCC, M, and SG treatments. Bulk density (D b ) of soil was 13% lower in M than the NCC. Saturated hydraulic conductivity (K sat ) values were positively correlated with most CT-measured pore parameters. In contrast, D b was negatively correlated with most CT-measured pore parameters (circularity and fractal dimension were positively correlated). While the circularity values were correlated positively with D b and thermal conductivity ( λ ), the fractal dimension was correlated positively with volumetric heat capacity ( C v ). The study illustrates that M and CC treatments can improve soil pore parameters. [ABSTRACT FROM AUTHOR]

Conversion of annual grain crop systems to biofuel production systems can restore soil hydrologic function; however, information on these effects is limited. Hence, the objective of this study was to evaluate the influence of topsoil thickness on water infiltration in claypan soils for grain and switchgrass ( Panicum virgatum L.) production systems. The experiment was performed at the University of Missouri South Farm (38°54′N, 92°16′W) on a Mexico silt loam (Vertic Luvisols) soil. Since 2009, plots were planted with either switchgrass or a corn ( Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation. Infiltration rates were measured using ponded infiltrometers during two years (2014 and 2015) under switchgrass and grain crop management each with two levels of topsoil thickness (0 and 37.5 cm). Physically-based Parlange and Green-Ampt infiltration models were used to estimate saturated hydraulic conductivity ( K s ) and sorptivity ( S ) parameters. Switchgrass planted on degraded soil (shallow topsoil treatment) resulted in greater K s , S , q s (quasi-steady infiltration rate) and K fs (field-saturated hydraulic conductivity) values than with row crop management for both 2014 and 2015 measurement years. Results for selected 24-hour mean frequency (11.8, 14.2, and 16.2 cm) storms showed that switchgrass production systems enhanced estimated water infiltration, reduced estimated runoff, and decreased estimated time from water ponding to end of ponding compared with row crop management. Switchgrass is recommended to be planted on degraded soils especially in claypan landscapes for improved water use. [ABSTRACT FROM AUTHOR]