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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]

Management is critical to maximize cover crop benefits, while minimizing costs. However, cover crop performance and cost can vary without consistent management strategies. Therefore, we investigated how four planting dates (late October, early November, late November, and early December), two seeding rates (67 and 101 kg ha−1), and four N rates (0, 34, 67, and 101 kg N ha−1) affected rye (Secale cereale L., 'Wrens Abruzzi') biomass production, N uptake, C:N ratio, $ per 100 kg biomass, cash crop yields, and soil organic C (SOC) in a peanut (Arachis hypogaea L.)/cotton (Gossypium hirsutum L.) rotation over six growing seasons (2015–2020) in Headland, Alabama, USA. Biomass production averaged 170% greater for late October planted rye compared to early December across all N rates. Nitrogen increased biomass production, but total biomass amounts decreased with later planting dates. Nitrogen uptake increased as N rate increased for each planting date. The C:N ratio was more sensitive to planting dates than N rates and decreased as planting was delayed. The $ per 100 kg of biomass was similar across all N rates for early planting dates (late October and early November). No yield effect was observed for peanut or cotton, but SOC increased in the 0–5 cm depth when 101 kg N ha−1 was applied to the rye cover crop. Results highlight the importance of planting date compared to seeding and N rates to enhance cover crop performance and return on investment (ROI) for growers in the southeastern United States. Core Ideas: Planting early (late October to early November) was crucial to enhance rye performance.Nitrogen improved rye biomass production, but the effect decreased with later planting dates.Rye biomass production was equal between 67 and 101 kg ha−1 seeding rates.Neither peanut nor cotton yields were affected by cover crop management factors.Soil surface soil organic C concentrations increased following rye that received 101 kg N ha−1. [ABSTRACT FROM AUTHOR]

The southeastern United States has a long history of soil degradation due to intensive agriculture and climatic factors. Conservation management practices such as cover cropping aim to improve soil productivity and restore soil health. Our objectives were to evaluate the performance of cover crops and their short‐term effects on soil health indicators for two southeastern soil types. Cover crop experiments were conducted at the Wiregrass (WREC) and Tennessee Valley (TVREC) Research and Extension Centers in Alabama from 2017 to 2021. Cover crop treatments included winter fallow, monocultures, and two‐ and three‐way mixtures of cereal rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and forage radish (Raphanus sativus L.) preceding a cotton (Gossypium hirsutum L.)–legume {peanut [Arachis hypogaea L.] or soybean [Glycine max (L.) Merr.]} cash crop rotation. At TVREC, aboveground biomass for both rye and clover were greater than radish. All cover crops, except the radish monoculture, increased soil organic carbon (SOC) 19–30% in the top 5 cm at TVREC compared with winter fallow. Similarly, some cover crop treatments increased permanganate oxidizable carbon (POXC) compared with the fallow control. However, this effect was not observed at WREC. Cover crops did not produce many meaningful aggregate stability differences at either location. Treatments containing rye or clover decreased soil strength. by 14–22% at TVREC after 4 yr of cover crop utilization. Short‐term cover crop use improved selected soil health indicators and reversed soil degradation at one location evaluated, but these benefits were dependent on soil type and cover crop selection. Core Ideas: Cover crop mixtures did not improve specific indicators of soil health more than monocultures.Radish monoculture did not improve soil health indicators compared with fallow.Rye and clover cover crops decreased compaction in a silt loam Ultisol after 4 yr.Cover crops increased soil C by 19‐30% in the top 5 cm of a silt loam Ultisol.Cover crops did not improve soil health indicators in a loamy sand Ultisol. [ABSTRACT FROM AUTHOR]

The restoration of soil health is a crucial step to maximize productivity in historically eroded soils of the southeastern United States. Cover crops have been known to improve soil health over time; therefore, studies were conducted from 2017 to 2019 in the Tennessee Valley (TVREC) and Wiregrass (WREC) Research and Extension Center regions of Alabama to examine the impact of cover crops on dynamic soil health indicators. Treatments including fallow, along with monocultures and combinations of cereal rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and Daikon radish (Raphanus sativus L.) were arranged in a randomized complete block design in cotton (Gossypium hirsutum L.)–legume cash crop rotations. Soil health indicators included permanganate oxidizable C (POXC), total C (TC), water stable aggregates (WSA), and soil strength (area under the curve for cone index [AUCCI]). Cover crops did not increase WSA compared with fallow after 2 yr of treatment. At TVREC, POXC in the 10‐to‐15‐cm depth increased 60.6% under crimson clover compared with fallow. At TVREC, TC increased in the top 15 cm of soil after 2 yr of crimson clover, rye–clover, and rye–radish compared with fallow by 14.3, 11.6, and 15.2%, respectively. No differences in AUCCI occurred between treatments in 2018 at either location. In 2019, AUCCI at TVREC was higher under fallow and radish treatments compared with rye and rye–radish, whereas AUCCI at WREC in 2019 was higher under clover‐containing treatments compared with fallow and rye. Overall, some improvements in soil health indicators were observed after 2 yr of cover crop utilization, but long‐term cover crop use may be necessary to observe more consistent soil health changes. Core Ideas: Cover crop mixtures did not increase biomass compared with rye or clover monoculture.Soil health indicators rarely differed after 2 yr of cover crop treatments.Total C increased in finer‐textured soils after 2 yr for some cover crops. [ABSTRACT FROM AUTHOR]

Brassica carinata, a nonfood oilseed crop, is used to produce renewable fuels because of its high oil content and favorable fatty acid profile. Production in the southeastern United States is relatively new, and information on agronomic management practices to optimize growth and yield is limited. Since optimal seeding rate may depend on the land preparation method for this small‐seeded crop, a study was conducted to evaluate the effect of tillage system (conventional, no‐till, broadcast‐disc, and ripper‐roller) and seeding rate (1.12, 5.60, 10.09, and 14.57 kg seed ha−1) on the performance of B. carinata. A randomized complete block design with a strip‐plot restriction on randomization and four replications was implemented in Headland, AL, Jay, FL, and Quincy, FL, over five site‐years during the 2017–2018 and 2018–2019 growing seasons. Data were collected on soil residue cover; plant population; soil penetrometer resistance and moisture; biomass (including carbon and nitrogen); stalk diameter; yield and yield components; seed oil, protein, and glucosinolates concentration; and oil composition. Soil penetrometer resistance was significantly affected by tillage system, with the ripper‐roller consistently having the lowest penetration resistance values across all site‐years. Ripper‐roller tillage had the highest oil content and lowest protein and glucosinolate contents. Yield response to tillage system was variable. Among seeding rate treatments, yield was lowest at 1.12 kg seed ha−1 and similar among 5.60, 10.09, and 14.57 kg seed ha−1 at all site‐years. There was no tillage by seeding rate interaction for yield. Results indicate that among seeding rate treatments used, 5.6 kg seed ha−1 rate was optimal at all site‐years regardless of land preparation method and is thus the recommended seeding rate for commercial carinata production in the Southeastern United States. [ABSTRACT FROM AUTHOR]

Grazing cover crops (CC) could provide an economic incentive to increase adoption rates in the southeastern United States. However, understanding grazing effects on soil properties is lacking for most soils of the region. Effects of grazing or rolling a cereal rye (Secale cereale L.) CC prior to no-till planting cotton (Gossypium hirsutum L.) were determined in 2009 after 4 yr on Cecil soil, in the Southern Piedmont near Watkinsville, GA. The four catchments had a previous long history of no-till cropping with CC. Wet spring conditions in 2009 resulted in visible surface roughness from cattle hooves. Average soil penetration resistance (PR) for the 0- to 30-cm profile was 14% greater following rye CC grazing than rolling (1.95 vs. 1.53 MPa) and was still apparent the following February (1.86 vs. 1.58 MPa) after cotton harvest. Increases in PR at 2.5- to 7.5- and 7.5- to 15-cm soil depths were observed following CC grazing but not rolling. Depth to 2 MPa resistance, considered sufficient to impede root growth, was similar for CC grazing and rolling treatments in March prior to grazing but decreased in the grazed treatment to 10.7 cm in May and 15.6 cm in February. Seasonal runoff data for 2006-2009 indicated no differences between grazed and rolled CC management. We concluded that grazing CC for short periods under wet conditions presents a risk of short-term negative effects even for Southern Piedmont soils where a long history of conservation tillage and CC has improved soil quality. [ABSTRACT FROM AUTHOR]

Regulations on nutrient application amounts and environmental impacts of fertilizers are promoting advances in agricultural management strategies to optimize irrigation application and N fertilization in corn. Previous studies have found a relationship between irrigation application, available water in the soil, and N fertilizer uptake. The objective of this study was to evaluate interactions between two irrigation scheduling methods and four N rate applications (0-control, 202, 269, and 336 kg ha−1) on grain yield, aboveground biomass, plant N concentration, N uptake, and nitrogen use efficiency in corn. The study was conducted at the Tennessee Valley Research and Extension Center (TVREC) during two growing seasons (2014 and 2015). The irrigation scheduling methods consisted of (i) the pan evaporation method, which is based on managing the crop's estimated evapotranspiration (ET) using pan evaporation values and the crop's consumptive water use and (ii) the sensor-based irrigation scheduling method based on soil matric potential values recorded by soil moisture tension sensors installed in the field. Irrigation amounts from both irrigation scheduling methods indicated that less water was applied with the sensor-based method. The different amounts of irrigation applied associated with the two irrigation scheduling methods did not impact grain yield, aboveground biomass, and NUE. In general, NUEs values decreased with increased N rates, which means that additional N fertilizer added to the soil was not converted into grain yield or/and adsorbed by plants; therefore, more N remained in the soil, increasing the risk for environmental problems. [ABSTRACT FROM AUTHOR]

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]

Corn (Zea mays L.) production in the Southeast can be negatively impacted by erratic summer rainfall and drought-prone, coarse-textured soils, but irrigation combined with conservation tillage and cover crops may support greater plant densities arranged in different row configurations to improve yield. We examined five site-years of data across two soil types in Alabama to compare corn yields in a conservation system across three plant densities for single- and twin-row configurations in dryland and irrigated moisture regimes. Treatments were arranged with a split plot treatment restriction in a RCB design with three replications. Main plots were irrigation level (no irrigation and irrigation), and subplots were a factorial arrangement of three plant densities (5.9, 7.4, and 8.9 plants m−2) and row configurations (single and twin). A moisture environment (low and moderate) variable, defined by growing season rainfall, was used to average over site-years. In general, irrigation in the moderate-moisture environment improved each measured variable (plant height, stover yield, corn yield, and test weight) and decreased grain N concentration and aflatoxin levels compared to the low-moisture environment with no irrigation. Benefits of increased rainfall and irrigation to reduce soil moisture stress across drought-prone soils were evident. Pooled results across all site-years indicated no yield response as plant density increased, but greater yields were observed with the greatest plant densities in the moderate-moisture environments. No advantage for twin-row corn production was observed across five site-years in Alabama, which indicates either row configuration can be successfully adopted. [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]

Winter cereal cover crops are necessary to achieve maximum benefits of conservation tillage in the southeastern United States. These benefits generally increase as cover crop biomass increases; therefore, we conducted a study to evaluate N application times, sources, and optimal rates to maximize cover crop biomass production at Headland, AL, on a Fuquay sand (loamy, kaolinitic, thermic Arenic Plinthic Kandiudults) during the 2006-2008 growing seasons. Treatments were arranged in a split-split plot treatment restriction in a randomized complete block design with four replications. Main plots were time of fertilizer application (fall and spring), subplots were N source (commercial fertilizer and poultry [Gallus gallus domesticus] litter), and sub-subplots were N rate (0, 34, 67, and 101 kg N ha-1 as commercial fertilizer and 0, 2.2, 4.5, and 6.7 Mg ha-1 as poultry litter [as-sampled basis]) for a cereal rye (Secale cereale L.) cover crop. Commercial fertilizer produced 13% greater biomass compared to poultry litter across all rates and application times. Lower biomass production and higher costs for poultry litter reduced the feasibility of poultry litter as an N source compared with commercial N. Higher C/N ratios were measured for fall-applied N compared to spring-applied N, while N fertilizer recovery efficiency (REN) averaged 37% across the experiment. Results indicated fall application of commercial fertilizer N produced superior results across cover crop responses examined in this study, while providing general information about N fertilizer requirements to increase surface residue associated with cover crops across the southeastern United States. [ABSTRACT FROM AUTHOR]

Soil degradation and rising production costs have prompted grower interest in conservation tillage with cover crops for peanut (Arachis hypogaea L.). Our objective was to evaluate single and twin row peanut production across three different strip tillage implements (KMC, Orthman, Unverferth) with and without a rye (Secale cereale L.) cover crop in Headland, AL, and Tifton, GA, during 2012 to 2014. Surface residue cover following planting, plant populations, peanut yield, total sound mature kernels (TSMK), and soil penetration resistance (PR) for the cultivar Georgia 06G were compared across cover crop treatments, tillage implements, and row patterns. Surface residue exceeded 60% at both locations in the rye treatment. Plant populations were greater across the fallow treatment and the twin row pattern at both locations. Twin rows increased yield compared with single rows in Headland (360 kg ha-1) and Tifton (>1000 kg ha-1) and also improved grade (TSMK) at both locations. Strip tillage implements had no effect on peanut plant parameters. At planting, soil PR was greater with a cover crop only at Headland; whereas implements reduced soil PR in 2012 (Orthman) and 2014 (Unverferth). At harvest, soil PR differences were only observed in 2013. The KMC and Unverferth implements maintained less resistance compared with Orthman at Headland, whereas cover crop reduced PR at Tifton. Peanut performance did not differ in response to one strip tillage implement over the other; however, results show strip tillage with a cover crop and twin row management improves peanut production across the Southeast. [ABSTRACT FROM AUTHOR]

Residue management is an important aspect of cropping systems. Availability of plant residue N to succeeding crops depends on N mineralization rates. Cooperative Extension currently recommends 22 to 67 kg N ha-1 credit to subsequent crops following peanut (Arachis hypogaea L.), but these recommendations are not supported in the literature, nor do they specify if the credit is applied to a subsequent winter or spring crop. The objective of this study was to assess N release rates from residues of three peanut cultivars (NC V-11, GA 02-C, and ANorden) at two placements (surface and 10-cm deep) and two locations representing northern and southern extremes of U.S. commercial peanut production (North Carolina and Alabama). Litterbags containing the equivalent of 3.5 Mg ha-1 were placed in a completely randomized design at both locations with four replications and retrieved periodically up to 335 d after application. Results were fit to single or double exponential decay models. Based on empirical models, the N credit to a subsequent winter wheat (Triticum aestivum L.) crop was estimated at 14 to 19 kg N ha-1 when peanut residues were buried after harvest, and 19 to 24 kg N ha-1 when on the soil surface. When N credits were applied to a subsequent cotton (Gossypium hirsutum L.) crop, they were reduced to 2 to 9 kg N ha-1 (buried) and 6 to 10 kg N ha-1 (surface). Current recommendations are higher than the results obtained in this study suggest and warrant re-examination. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium hirsutum L.) producers in Alabama are faced with a rapidly expanding problem that decreases yields and increases production costs: herbicide-resistant weeds. Producers increasingly rely on integrated weed management strategies that raise production costs. This analysis evaluated how tillage, cover crops, and herbicide regime affected net returns above variable treatment costs (net returns) for cotton production in Alabama from 2009 to 2011 under pressure from Palmer amaranth (Amaranthus palmeri S. Wats.). Annual net returns were compared for two tillage treatments (inversion and noninversion tillage), three cover crops (crimson clover [Trifolium incarnatum L.], cereal rye [Secale cereal L.], and winter fallow), and three herbicide regimes (PRE, POST, and PRE+POST). Results indicate that under heavy Palmer amaranth population densities one year of inversion tillage followed by two years of noninversion tillage, along with a POST or PRE+POST herbicide application had the highest net returns in the first year; however, the economic benefit of inversion tillage, across all herbicide treatments, was nonexistent in 2010 and 2011. Cotton producers with Palmer amaranth infestations would likely benefit from cultural controls, in conjunction with herbicide applications, as part of their weed management system to increase net returns. [ABSTRACT FROM AUTHOR]

Soil penetrometers measure penetration resistance to characterize soil strength for different management practices, primarily tillage. Our objective was to demonstrate a simple approach to quantify soil strength differences among treatments collected with a multiprobe cone penetrometer using cone index measurements to complement contour graphs and statistical analyses. The approach involves obtaining average cone index values by row position and calculating the area under the curve for cone index (AUCC.I.), with units of megapascal-centimeters (MPa-cm). Data were collected from a tillage and cover crop experiment in Prattville, AL (November 2009), and at the Old Rotation experiment in Auburn, AL (December 2014). Cone index values were averaged across depths for five row positions perpendicular to the center of the row (0 cm) and 22.5 and 45 cm on either side of the crop row. The approach identified that three conservation tillage implements reduced penetration resistance compared with no tillage based on AUCC.I. values from the Prattville experiment. Although no statistical comparisons were possible from the unreplicated Old Rotation experiment, AUCC.I. values were numerically lower for the 3-yr rotation compared with continuous cotton (Gossypium hirsutum L.) and the 2-yr rotation. Results from both sets of cone index measurements demonstrated that the area under the curve (AUC) approach can be used to quantitatively distinguish among treatments. Results from the AUC approach can be used to facilitate simple comparisons among treatments in field experiments and aid in the interpretation of traditional statistical analyses combined with contour graphs. [ABSTRACT FROM AUTHOR]

Corn (Zea mays L.) production for grain is important given its many uses for human food, animal feed, and other industrial products. Additionally, the abundance and potentially large biomass yield makes corn an attractive bioenergy feedstock. The objective of this study was to evaluate the effect of in-season weather conditions, rye (Secale cereale L.) as a winter cover crop, and corn residue harvest on grain yield and biomass distribution across two soil types. Grain, as well as, total and partial stover yields (below the ear, above the ear excluding cobs, cobs alone, and above the ear including top and cobs) were measured from 2009 to 2011 at two sites with different soil types: loamy sand and silt loam, in central and northern Alabama, respectively. Significant differences in grain and biomass yields were observed among individual years and locations. Grain yields were positively correlated with seasonal cumulative precipitation and negatively with seasonal average temperature at both locations. In central Alabama, the 3-yr use of a rye cover crop increased corn biomass yields compared to rye removal while there was no difference compared to plots without a rye cover crop. The 3-yr corn residue management effect was not significant at any location. Based on this study, harvesting the above-ear corn plant fraction could be an attractive option for partial biomass harvesting in southeastern United States. [ABSTRACT FROM AUTHOR]

The use of crop canopy sensors for variable rate nitrogen (VRN) application in corn (Zea mays L.) production across the southeastern United States implies assessment of corn N status as early as the V6 growth stage. Our goals were to identify vegetation indices (Vis) that best: (i) correlate with plant status variables such as leaf area index (LAI) and leaf chlorophyll (Chi) and (ii) predict corn grain yield at early growth stages. An N fertilization study was conducted between 2010 and 2012 at three Alabama sites. Six N fertilizer rates (0-280 kg N ha-1 on 56 kg N ha-1 increments) were applied at planting. Data collected at V6, V8, V10 vegetative growth stages were leaf Chi, LAI, and spectral reflectance. Data showed that corn N response could be influenced by the rainfall pre- and post- N application as well as the soil texture. Among 11 vegetation indices evaluated through a canonical correlation analysis, the normalized difference red-edge (NDRE), Chi index red-edge [CI (RE)], simple ratio red-edge [SR (RE)], and inverse simple ratio red-edge [ISR (RE)] had the strong correlation with plant status variables. Vegetation index-based corn yield prediction was the lowest at V6 and the highest at V10 stage. At V8 and V10 stages, the yield models based on NDRE, CI (RE), or SR (RE) explained most of yield variation. These results indicated that early season estimation of crop N status and yield potential may be more accurate if red-edge vegetation indices are used. [ABSTRACT FROM AUTHOR]

Constituent determination of biomass for theoretical ethanol yield ( TEY) estimation requires the removal of nonstructural carbohydrates prior to analysis to prevent interference with the analytical procedure. According to the accepted US Department of Energy-National Renewable Energy Laboratory ( NREL) method, biomass extractives in corn stover should be removed by a two-step extraction process. Alternatively, Neutral Detergent Fiber method ( NDF) is a fast and cost-effective method used to determine structural carbohydrates of forage biomass. The objective of this study was to determine whether the NDF method can be used as an alternative to the NREL extraction procedure for corn ( Zea mays L.) stover biomass. Arabinan content varied between the two methods. However, glucan, xylan, and TEYs were not statistically different. Furthermore, the average TEYs per unit of mass and unit of area varied by 2.0 and 1.9%, respectively. Additionally, the NDF extraction procedure was faster and less expensive than the NREL procedure. [ABSTRACT FROM AUTHOR]

Tillage systems that promote minimal surface disturbance combined with high residue cover crops can sequester C, but additional research to quantify carbon sequestration with conservation agricultural systems is needed for modelers, policymakers, and landowners. A factorial arrangement of conservation tillage (no-till, fall paratill, spring paratill, and spring strip-till) and winter cover crops (no cover, rye [Secale cereale L.], and wheat [Triticum aestivum L.]) were established in a corn/cotton (Zea mays L./Gossypium hirsutum L.) rotation from 2004 to 2009 to (i) evaluate cover crop biomass production and associated changes in soil organic carbon (SOC) to 15 cm, (ii) evaluate the potential of conservation systems to sequester SOC after years of conventional tillage, and (iii) compare measured changes in SOC to predicted soil conditioning index (SCI) values. Carbon returned to the soil each year averaged 2500 and 1340 kg C ha-1 for cover crops and corn residue, respectively. The average SOC sequestration rate in the top 15 cm was 926 ± 344 kg C ha-1 yr-1. Soil organic C values measured after 6 yr related well with predicted SCI values (r² = 0.81; P = 0.0004). However, discrepancies between SCI and SOC values for conservation systems highlighted the need to improve the SCI for the Southeast U.S. Conservation systems following years of conventional monocropping were equivalent in their ability to sequester considerable amounts of C that will improve soil quality in the Coastal Plain of the southeastern USA. [ABSTRACT FROM AUTHOR]

Estimating corn (Zea mays L.) grain and stover yield during the growing season is an appealing idea. An accurate yield estimation could benefit farmers, as well as corn-related industries. The objective of this study was to develop regression equations to estimate corn grain and stover yield using easily accessible information (N fertilization rate and cumulative precipitation), and simple plant morphological measurements such as height, stem diameter at various heights, height of the first ear, and plants per hectare. Measurements made at silking (R1) were used since the maximum explainable variability would not exceed 58% at early stages of plant development (V2-V10; between 2-leaf and 10-leaf stages). The experiment was conducted from 2009 until 2011 in two locations, in north and central Alabama, under no-tillage and non-irrigated conditions. Treatments were assigned to a 3 x 4 x 2 complete factorial design arranged in a split-split-plot with three replications. Factors were; winter rye (Secale cereale L.) cover crop (main plot), N fertilization rates (subplot), and stover residue harvest (sub-subplot). All measurements from this study, across years and locations, were used in the final regression equations to create robust prediction models. Equations, with and without intercept, were developed and compared according to several statistical criteria. The final grain yield equation at R1 growth stage included an intercept with a R² of 0.7705. The final stover equation also included an intercept (R² = 0.8473). This study suggests that N rate, total precipitation amount from planting until silking, and simple plant morphological measurements can be used to predict corn yield. [ABSTRACT FROM AUTHOR]

In the Southeast, winter wheat (Triticum aestivum L.) is typically planted from late October to early December. However, grain yield is reduced by an interaction of weather, soil, and plant factors. From 2009 to 2012 a study was conducted at three locations in Alabama to evaluate the seeding date effect on yield and yield components of three cultivars. The AGS 2060, AGS 2035, and Baldwin cultivars were evaluated within four seeding dates at approximately 15-d intervals. Results showed that grain yield, spikes per m², and kernel weight declined linearly with seeding delay; however, the impact changed among years and locations within a year. The variability of kernels per spike was location specific, in the north delayed planting resulted in a greater number of kernels per spike while the opposite occurred at the central and southern locations. At most location--year combinations, seeding 2 to 4 wk later than the Extension's best seeding date resulted in yield losses; especially if warm and dry conditions were prevalent during winter and spring months at locations with sandy loam soils. Under warm and dry growing conditions, the impact of delayed planting on yield and kernel weight was the greatest for Baldwin and AGS 2035 and least for the AGS 2060. In contrast, when cold and wet growing conditions were prevalent, there were not significant planting date differences on yield and yield components. Cultivar and seeding date should be selected on a location basis due to the plant interactions with soil and weather factors. [ABSTRACT FROM AUTHOR]

Soil management practices influence soil physical and chemical characteristics and bring about changes in the soil microbial community structure and function. In this study, the effects of long-term conventional and no-tillage practices on microbial community structure, enzyme activities, and selected physicochemical properties were determined in a continuous corn system on a Decatur silt loam soil. The long-term no-tillage treatment resulted in higher soil carbon and nitrogen contents, viable microbial biomass, and phosphatase activities at the 0-5 cm depth than the conventional tillage treatment. Soil microbial community structure assessed using phospholipid fatty acid (PLFA) analysis and automated ribosomal intergenic spacer analysis (ARISA) varied by tillage practice and soil depth. The abundance of PLFAs indicative of fungi, bacteria, arbuscular mycorrhizal fungi, and actinobacteria was consistently higher in the no-till surface soil. Results of principal components analysis based on soil physicochemical and enzyme variables were in agreement with those based on PLFA and ARISA profiles. Soil organic carbon was positively correlated with most of the PLFA biomarkers. These results indicate that tillage practice and soil depth were two important factors affecting soil microbial community structure and activity, and conservation tillage practices improve both physicochemical and microbiological properties of soil. [ABSTRACT FROM AUTHOR]

Sunn hemp (Crotalaria juncea L.) is a tropical legume that produces plant biomass and nitrogen (N) quickly. Our objectives were to assess the growth of a new sunn hemp cultivar breed to produce seed in a temperate climate and determine the residual N effect on a rye (Secale cereale L.) cover crop in east-central Alabama from 2007 to 2009. Plant populations, plant height, stem diameter, biomass production, and N content were determined for two sunn hemp planting dates, following corn (Zea mays L.) and wheat (Triticum aestivum L.) harvest, across different seeding rates (17, 34, 50, and 67 kg/ha). Rye biomass was measured the following spring. Sunn hemp biomass production was inconsistent across planting dates, but did relate to growing degree accumulation. Nitrogen concentrations were inversely related to biomass production, and subsequent N contents corresponded to biomass levels. Neither planting date nor seeding rate affected rye biomass production, but rye biomass averaged over both planting dates following wheat/sunn hemp averaged 43% and 33% greater than rye following fallow. Rye biomass following corn/sunn hemp was equivalent to fallow plots. Early planting dates are recommended for sunn hemp with seeding rates between 17 and 34 kg/ha to maximize biomass and N production. [ABSTRACT FROM AUTHOR]

Evaluates the management practices of nitrogen on the watershed scale through testing the soils and cornstalks. Measurement of the sufficiency level of nitrogen; Efficiency of nitrogen fertilization; Reflection on the effect of spring weather conditions.