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The tropical legume sunn hemp (Crotalaria junceaL.) cultivar ‘AU Golden’ has the potential to provide substantial nitrogen (N) to subsequent crops to reduce recommended application rates of synthetic N fertilizers. A mineralization field trial was conducted to measure mass decomposition and N and carbon (C) amounts remaining from sunn hemp residue following three planting dates (May, June, and July) during the 2013 growing season at the Tennessee Valley (TVS) and Coastal Plain (WGS) locations of AL. Residue from June and July plantings contained 50.0% and 61.1% N at WGS and 41.5% and 66.5% N at TVS by the end of their respective incubation periods compared to residue from the May planting, which contained 21.1% N at WGS and 47.8% at TVS. In order to create a more synchronous relationship between ‘AU Golden’ residue N mineralization and crop demand, termination must be delayed until approximate planting of the following crop. [ABSTRACT FROM PUBLISHER]

Studies have shown that conversion to conservation tillage from conventional tillage does not increase total soil organic carbon (SOC) significantly in the short term (<5 yrs). While no-till increases total SOC in the medium to long term, it was hypothesized that the inclusion of high biomass cover crops and organic mulches may increase total SOC in the short term. The use of invasive, perennial leguminous species as mulch may sustainably increase SOC during limited-input fall vegetable production. The objective of this study, conducted in Alabama (USA), was to quantify total SOC changes due to organic mulches and forage soybean (Glycine max(L.) Merr. cv. Derry) as a summer cover crop after conversion to no-till during limited-input fall collard (Brassica oleraceaL.) production. Forage soybean as a summer cover crop did not increase SOC. No-till without mulch (control treatment) significantly increased SOC at 0–5 cm from 6.3 to 14.0 g kg−1soil in 3 yrs, whereas inclusion of cut-and-carry mulches increased SOC to ≥22.6 g kg−1soil. Treatments did not affect collard yield, which averaged 17,863 kg ha−1yr−1. This represents a novel, limited-input system that may help control on-farm invasive species while sustainably increasing SOC in the short term. [ABSTRACT FROM PUBLISHER]

The southeastern U.S. has a tremendous potential to grow a biomass crop during winter months when cash crops are not normally produced. These cover crops have proven to be extremely valuable to reduce soil erosion and improve soil quality. However, an opportunity to potentially harvest a portion of the cover crop for bioenergy purposes exists and needs to be considered to maximize the production potential of southeastern soils. An experiment was performed to determine if harvesting these cover crops could adversely affect soil properties or subsequent cash and cover crop yields. The experiment also included the effects of conducting an in-row subsoiling operation at different times of the year. Results from cone index measurements indicated that soil strength was significantly increased when the cover crop was harvested and not left on the soil surface to decompose. Not surprisingly, cotton and peanut cash crop yields declined by an average of 9% when the cover crop was harvested. Succeeding cover crop yields were also reduced by 17% due to the harvesting of previous cover crops. Conducting an in-row subsoiling operation in the fall of the year prior to planting the cover crop increased cover crop biomass by more than 18% over spring in-row subsoiling but had little impact on cash crop yields. Recommendations from this study should include a caution to producers who may want to consider their cover crops as a potential bioenergy crop. Reductions in both cash and cover crop production can result if cover crops are harvested instead of left on the surface to enhance soil quality. Additionally, scheduling a necessary in-row subsoiling operation in the fall of the year instead of waiting until the spring will improve cover crop yields. [ABSTRACT FROM AUTHOR]

Estimating soil hydraulic properties, such as infiltration rate and hydraulic conductivity, is important for understanding hydrological processes such as rainfall and irrigation partitioning. Current infiltrometers can require considerable operator input to limit the number of readings that can be simultaneously performed. Therefore, the objective of this work was to develop a simple double-ring infiltrometer for automated data collection under falling head conditions. The design consisted of 15.2-cm tall inner- and outer-rings of 14.6 and 33.0 cm in diameter, respectively. The inner-ring was held in the centre of the outer-ring by a small pipe that also served as a handle. A small hole was drilled 3.8 cm from the bottom of each ring and a slightly larger hose passed through both holes. One hose end led into the inside of the inner-ring and the opposite end to the outside of the outer-ring. A pressure transducer was attached to the outside end of the hose. A datalogger was used to record the transducer output. This design was compared in-situ to a constant head method using a Mariotte bottle system on two distinct soils and tested on four different soil series ranging in textural class from a loamy sand to a clay. Soils had been fallow prior to this work for at least 2 years, except the loamy sand which had a 5-year-old Bahia grass ( Paspalum notatum) stand. Although there were some differences between the two approaches, values estimated with the proposed method had less variability. This method allows a single user to collect multiple readings. Collected data can be used to estimate quasi-steady state and cumulative infiltration, and in situ hydraulic conductivity of saturated soil. The proposed procedure could be beneficial when multiple readings of soil hydraulic properties are required, such as when characterizing soil spatial variability. [ABSTRACT FROM AUTHOR]

Soil nutrient concentrations vary with soil management system and landscape position, but limited information exists describing these interactions within a heterogeneous field. A three year experiment was conducted to evaluate pH, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and zinc (Zn) concentrations at three depths, 0 to 5 cm, 5 to 15 cm, and 15 to 30 cm (0 to 2 in, 2 to 6 in, and 6 to 12 in), and three landscape positions, summit, sideslope, and drainageway, in a 9 ha (22 ac) field containing four different management systems. Management systems consisted of a conventional (chisel plowing/disking in-row subsoiling with no cover crops) and conservation tillage system (in-row subsoiling with cover crops) with or without dairy bedding manure. Soils ranged from Aquic to Typic Paleudults. Manure applications increased pH and nutrient concentrations in the soil surface at 0 to 5 cm (0 to 2 in) of conventional and conservation tillage systems, with highest values measured in conservation tillage. Landscape position affected soil pH and P concentrations; however, depth and landscape position interactions were observed for soil pH, P, and K concentrations. The lowest soil pH and P concentrations were measured from the sideslope position, while K concentrations did not exhibit consistent distributions across landscape positions. Future soil testing of Coastal Plain fields to account for erosion of the landscape may help direct future sampling methodology and interpretations for nutrient management. [ABSTRACT FROM AUTHOR]