Search

Introducing integrated crop‐livestock systems into row crop production promotes income diversification and potential soil health benefits through cover crop grazing on degraded soils of the southeastern United States, but effects of these practices on crop yields and soil health in Coastal Plain soils are not well established. A 4‐year study was performed to evaluate the effects of grazing a multi‐species winter cover crop on soil health and crop yields under mid‐February, mid‐March, and mid‐April cattle removal dates and a non‐grazed control within an annual cotton (Gossypium hirsutum L.) and peanut crop rotation (Arachis hypogaea L.). Chemical soil health indicators (soil organic carbon and permanganate oxidizable carbon), physical soil health indicators (water‐stable aggregates and penetration resistance), biological soil health indicators (microbial biomass carbon, soil respiration, and arbuscular mycorrhizal fungi colonization), crop yield, and cover crop biomass were evaluated. Cover crop biomass at termination was reduced by 3660, 5250, and 5610 kg ha−1 for the mid‐February, mid‐March, and mid‐April cattle removal treatments compared to the non‐grazed control. No grazing treatment effects were observed for biological soil properties. Soil organic carbon was higher in the non‐grazed treatment than the mid‐April grazing treatment across 0‐ to 30‐cm depth. Penetration resistance across 0‐ to 50‐cm depth and water‐stable aggregates at the 0‐ to 30‐cm depth were both negatively impacted by increased grazing period lengths. Results from this study suggest that longer cover crop grazing periods have little effect on biological and chemical soil health indicators in the short term but can negatively impact some physical soil health indicators. Core Ideas: Grazing cover crops has minimal effects on biological soil health indicators.Longer grazing periods can have more negative effects on soil physical health indicators.Improvements in soil organic carbon levels were highest in the non‐grazed treatment. [ABSTRACT FROM AUTHOR]

State‐level cooperative extension services provide fertilizer recommendations for row crops in the United States. Of these, nitrogen (N) recommendations are arguably the most important because N is the most common yield‐limiting nutrient in nonlegume crop production systems. Throughout the peanut (Arachis hypogaea L.) growing region of the United States, Cooperative Extension Services generally recommends 22–67 kg N/ha credit to crops following peanut, likely due to the assumption that peanut, being a legume, contributes N to the following crop. The body of peer‐reviewed literature indicates that N credits from peanut to the subsequent crop are negligible. Recent literature indicates that apparent differences in yield following peanut compared to a nonlegume are a result of nonlegume crop residue favoring N immobilization rather than N mineralization from peanut residue. Taken together, recent research corroborates the few previous scientific publications addressing the issue, namely, that cooperative extension service recommendations to reduce N fertilization to crops after peanut are not supported by the peer‐reviewed literature. Future field research should include summer fallows to determine if yield differences between legumes and nonlegumes are due to N credits by the legume or N immobilization by nonlegumes. Data on N loss pathways following peanut are needed to identify management strategies that can mitigate N losses after peanut harvest. In conclusion, the preponderance of peer‐reviewed science does not support current Extension recommendations regarding peanut N credits to the following crop. Core Ideas: Nitrogen (N) credits from peanut to the subsequent crop are negligible.Data on N loss pathways following peanut are needed to identify management strategies that can mitigate N losses after peanut harvest.Peer‐reviewed science does not support current Extension recommendations regarding peanut N credits to the following crop. [ABSTRACT FROM AUTHOR]

Best management practices that optimize agronomic performance and make Brassica carinata production compatible with existing cropping systems are crucial for the establishment of a carinata supply chain in the southeastern United States. To this end, research was carried out to quantify land preparation method (conventional, no-till, broadcast-disc, and ripper-roller) and seeding rate effects on (1.12, 5.60, 10.09, and 14.57 kg seed ha−1) on B. carinata physiology, yield, and seed chemical composition. Data were collected on days to 50% flowering; canopy cover; gaseous exchange parameters (leaf net photosynthesis, stomatal conductance, transpiration, intercellular CO2, and water use efficiency); leaf area index; root weight; shoot weight; aboveground biomass; yield; and seed chemical composition. Leaf net photosynthesis was affected by land preparation treatment, being greater under the ripper-roller treatment, particularly during bolting. On the other hand, a decrease in photosynthesis, stomatal conductance, and water use efficiency was observed as seeding rate increased, especially during bolting. Carinata seed under the ripper-roller land preparation had the greatest oil content but lowest glucosinolates and protein contents. Yield did not respond to land preparation. Yield was minimized (732 kg seed ha−1) at the 1.12 kg ha−1 seeding rate and maximized (1087 kg seed ha−1) at the 5.6 kg ha−1 seeding rate. No land preparation by seeding rate interaction was observed for gas exchange parameters and LAI during any of the growth stages, nor was any interaction observed for yield. Carinata's physiological response to seeding rate did not depend on land preparation method employed. [ABSTRACT FROM AUTHOR]

Simulation models integrate our knowledge of soil organic C (SOC) dynamics and are useful tools for evaluating impacts of crop management on soil C sequestration; yet, they require local calibration. Our objectives were to calibrate the Environmental Policy Integrated Climate (EPIC) model, and evaluate its performance for simulating SOC fractions as affected by soil landscape and management. An automated parameter optimization procedure was used to calibrate the model for a site-specific experiment in the Coastal Plain of central Alabama. The ability of EPIC to predict corn (Zea mays L.) and cotton (Gossypium hirsutum L.) yields and SOC dynamics on different soil landscape positions (summit, sideslope, and drainageway) during the initial period of conservation tillage adoption (5 yr) was evaluated using regression and mean squared deviations. Simulated yield explained 88% of measured yield variation, with the greatest disagreement on the sideslope position and the greatest agreement in the drainageway. Simulations explained approximately 1, 34, and 40% of the total variation in microbial biomass C (MBC), particulate organic C (POC), and total organic C (TOC), respectively. The lowest errors in TOC simulations (0-20 cm) were found on the sideslope and summit. We conclude that the automated parameterization was generally successful, although further work is needed to refine the MBC and POC fractions, and to improve EPIC predictions of SOC dynamics with depth. Overall, EPIC was sensitive to spatial differences in C fractions that resulted from differing soil landscape positions. The model needs additional refinement for accurate simulations of field-scale SOC dynamics affected by short-term management decisions. Abbreviations: CT, conventional tillage; CTm, conventional tillage plus manure; EPIC, Environmental Policy Integrated Climate; FHP, fraction of humus in the passive pool; HI, harvest index; MBC, microbial biomass carbon; MSD, mean squared deviation; NT, no-till; NTm, no-till plus manure; PARM 20, microbial decay rate; PARM 51, microbial activity in the top layer; POC, particulate organic carbon; SOC, soil organic carbon; SOM, soil organic matter; TOC, total organic carbon; WA, biomass/energy ratio.

Field observations have shown that a substantial portion of peanut leaves abscise in windrows during pod curing, leading to an uneven distribution of leaves and stems when intact residues are spread during harvest. Possible differences in nitrogen (N) mineralization rates between peanut leaf and stem residues may lead to spatial and temporal variability in available N during subsequent crops. The objective of this study was to quantify N mineralization in soil amended with different peanut residue components under simulated conventional and conservation tillage practices. A 252‐day microlysimeter incubation was conducted in which peanut leaves, stems and a 1:1 mixture of leaves:stems from three varieties were incorporated or placed on the soil surface to simulate conventional or conservation tillage, respectively. Soils were periodically leached to assess N mineralization compared with a soil‐only control. Nitrogen mineralization was only affected by residue component. Averaged over variety and residue placement, soil amended with leaves mineralized 10% more N relative to the control or soil containing stems. It was estimated that leaves supplied 25 kg N ha−1 over 252 days at 0–15 cm soil depth, which would likely be insufficient to induce a yield response by a subsequent crop. This study suggests that uneven distribution of peanut leaf and stem residues following harvest causes only minor spatial and temporal variability in available N during subsequent crop growth. These results support the growing body of evidence indicating that peanut residue N contributions to subsequent crops are negligible in the peanut basin of the south‐eastern USA. [ABSTRACT FROM AUTHOR]

Core Ideas: Cover crop biomass responded linearly to N, but N response varied by species.Average nitrogen uptake efficiency of applied N was similar between oat and rye.Ryegrass consistently produced measured values less than oat and rye. A cereal cover crop combined with conservation tillage can enhance soil productivity of degraded southeastern soils. Direct comparisons regarding performance of different cereal cover crops are limited. This experiment, located at Auburn University's Wiregrass Research and Extension Center in Headland, AL on a Fuquay sand (loamy, kaolinitic, thermic Arenic Plinthic Kandiudults), was designed to compare cover crop biomass performance across nitrogen (N) rates during the 2009 to 2012 growing seasons. The experiment consisted of a randomized complete block design with a split plot restriction. Main plots were cover crops [oat (Avena sativa L.), rye (Secale cereale L.), and ryegrass (Lolium multiflorum L.)] and subplots were N rate (0, 30, 60, and 90 lb N/ac as commercial fertilizer). Cover crop biomass responded linearly to applied N (P = < 0.0001), but biomass response to N varied by cover crops (cover crop × N rate; P = 0.0001). Nitrogen content also responded linearly to applied N (P = < 0.0001), and the response to N varied across cover crops (cover crop × N rate; P = 0.0044). Average maximum carbon (C)/N ratios were greatest for rye, followed by oat and ryegrass; however, 30 lb N/ac produced the highest ratios, regardless of species. Average nitrogen uptake efficiency (NUE) of oat (54%) and rye (57%) were similar, but averaged 164% greater than average NUE of ryegrass (21%). These results support applying N fertilizer to rye or oat as a single species cover crop when high biomass production is preferred. [ABSTRACT FROM AUTHOR]