Ted S. Kornecki

Utilizing cover crop mulches to reduce tillage in organic systems in the southeastern USA

Organic systems in the southeastern USA offer unique challenges and solutions to crop production due to regional soil and climate characterized by highly weathered soil types, high precipitation and the capacity to grow cover crops in the winter. Recently, the interest of producers and researchers in high-residue cover crops and conservation tillage systems has increased. Various designs of the roller–crimper to manage cover crops have been invented and demonstrated to growers in the southeastern region of the USA over the past 17 years. The impacts of high-residue cover crop mulches on the agronomic systems in the region are diverse. Legume cover crops assist with meeting N demand from cash crops though they decompose rapidly and are seldom sufficient for N demanding crops such as corn. Cereal cover crop mulches can have the opposite effect by immobilizing N and have a longer impact on soil moisture and weed dynamics. While undesirable for many crops, N immobilization is one possible mechanism for weed suppression in legume cash crops planted into cereal residues. Other cover crop weed suppression mechanisms include physical impedance, light availability, allelopathy and microclimate effects. Regardless of the cause, successful weed control by mulches is highly dependent on having substantial biomass. The southeastern region is capable of producing cover crop biomass in excess of 9000 kg ha −1 , which is sufficient for weed control in many cash crops, although supplementary weed control is sometimes necessary. Long-term data are needed to predict when farmers should add supplementary weed control. More work is also needed on how much additional N is required for the cash crops and how best to deliver that N in a high-residue environment using organic sources.

New roller crimper concepts for mechanical termination of cover crops in conservation agriculture

Rollers crimpers have been used in conservation agriculture to terminate cover crops; however, excessive vibration generated by the original straight-bar roller design has delayed adoption of this technology in the United States. To avoid excessive vibration, producers generally reduce operating speeds that increase the time needed to perform the field operation. The objectives of this research were to identify roller crimper designs that terminated rye cover crops consistently, resulted in soil moisture conservation after use, and minimized vibrations when operated in the field. Six different roller types were developed and tested at 3.2 and 6.4 km h - 1 in Alabama field experiments during the 2006, 2007 and 2008 growing seasons. All roller types were used alone and one also in combination with glyphosate. Rye mortalities were evaluated 1, 2 and 3 weeks after rolling and compared with the check (non-rolled standing rye). Soil volumetric moisture content (VMC) was measured at the day of rolling, and then at 1, 2 and 3 weeks after rolling. Vibration was measured on the rollers’ and tractor’s frames during operation. Mortality for rolled rye 2 weeks after rolling was at least 98% compared with 96% for the check in 2006, 93% for rolling compared with 75% for the check in 2007, and 94% for rolling compared with 60% for the check in 2008 (P < 0.10). There were no consistent differences in rye mortality across roller types (without glyphosate) and speeds. VMC for soil in non-rolled rye plots was consistently lower than in rolled rye plots, averaging 3% compared with 7% 2 weeks after rolling in 2006, and 4% compared with 8% in 2008. During 2007, VMC was affected by severe drought conditions, and differences between roller treatments were detected but minor. The - 1 - 2 straight-bar roller generated the highest vibration on the tractor’s frame at 6.4 km h (0.71 m s , RMS), which exceeded International Standards (International Standard Office (ISO)). At 6.4 km h - 1 , new roller designs generated significantly lower acceleration levels from 0.12 to 0.32 m s - 2 on the tractor’s frame and were below detrimental effects on health ‘health limits’ classified by ISO. Overall, 2 weeks after rolling, all roller designs effectively terminated rye above 90%, which is the recommended termination level of rye to plant a cash crop into residue mat, while protecting soil surface from water loss. New roller designs generate less vibration than the original design and can be used safely at higher operating speeds.

Impact of Rye Rolling Direction and Different No-Till Row Cleaners on Cotton Emergence and Yield

Cover crops have been recognized as a vital component of conservation agriculture. However, cover crops must produce substantial biomass to be effective. Because of the large amount of residue produced by many cover crops, they must be managed appropriately to avoid planting problems. Roller-crimpers have been used to manage cover crops by flattening them and creating a thick mat over the soil surface. A study was conducted to determine the effect of different rolling directions (parallel, diagonal, and perpendicular to cotton planting direction) using a roller/crimper, three different commercial row cleaners (Dawn, Dawn without coulter, and Yetter), and no row cleaner on cotton (Gossypium hirsutum L.) stand, emergence rate, yield, and net returns. The study was conducted at two Alabama locations with a replicated strip plot design. Presented results illustrate two growing and harvest seasons (2004 and 2005). Rye (Secale cereale L.) was chosen as the cover crop due to its potential to produce large amounts of biomass and its popularity with Alabama producers. Rye was rolled at the soft dough growth stage and terminated using Roundup (glyphosate). Data showed that parallel rolling with respect to the planting direction for cotton produced the highest cotton stand and yield in both years. In 2004, the Yetter row cleaner resulted in higher cotton stand and yield for both locations when compared with the Dawn row cleaner. However, in 2005, the Dawn row cleaner resulted in a greater cotton yield than the Yetter. Based on the emergence rate index (ERI), the most rapid emergence was observed with parallel rolling and both row cleaners. The slowest emergence rate was observed with perpendicular and diagonal rolling and no row cleaners. Parallel rolling minimized accumulated rye residue on the row cleaners and minimized the cleaning time for the row cleaners. General findings from this research are: for tall rye producing large biomass, parallel rolling and Dawn or Yetter row cleaners are recommended. For shorter rye producing low biomass, no row cleaners were required for rolled rye with the parallel rolling direction, or cotton could be planted into standing rye using Dawn or Yetter row cleaners. Regardless of the height and amount of rye residue and the row cleaner type, the perpendicular and diagonal rolling directions are not recommended.

Determination of cationic and anionic surfactant concentrations in soil

Recently, surfactants have been given serious consideration with respect to their potential use in environmental remediation. Proposed in situ clean-up efforts focus on utilizing surfactants to solubilize/emulsify organic contaminants or to desorb heavy metals. Anionic surfactants are the type most likely to be used for removal of organics, whereas cationic surfactants may have application for displacement and mobilization ofheavy metals. Research within this field often requires determination of anionic and cationic surfactant concentrations in soil. This paper details a study through which simple and effective extraction procedures were established for use in conjunction with two different surfactant chemical analysis methods. Surfactant extraction is accomplished in two steps. First, a sodium chloride solution is used to reduce electrostatic soil/surfactant attractions and precipitation, and second, acetone is added to minimize hydrophobic adsorption. The extractant solution was diluted, followed by colorimetric chemical analysis using a spectrophotometer. The extraction effectiveness of these procedures was found to be near 100% for both cationic and anionic surfactants.

Net returns and risk for cover crop use in Alabama tomato production

Tomato (Solanum lycopersicum L.) producers are faced with uncertain yields and prices, and utilizing a production system that will reduce risk while maintaining yield may keep tomato producers economically sustainable into the future. A conservation tillage production system with high biomass cover crops may be an economically viable alternative for tomato producers in Alabama. The objective of this study was to compare the economics of alternative production systems using different cover crops, such as cereal rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.), and different subsoiler shanks for fresh-market tomato production relative to a commonly used plastic mulch system to determine the preferred treatment. Gross revenues and net returns from tomato production using a rye cover crop were higher than tomato production using plastic mulch in 2 of the 4 years. For the clover cover crop, gross revenues and net returns were higher in 1 out of the 4 years. Under tomato prices and weather conditions observed during 2005–2008, the preferred treatment for a risk neutral producer was planting tomatoes into a rye cover crop with a wide shank. For a strongly risk averse producer, all cover crop treatments were preferred to plastic mulch. The use of a cover crop in tomato production has the potential to be an equally profitable, less risky alternative to plastic mulch in Alabama.

EFFECTS OF COVER CROP REMOVAL ON A COTTON-PEANUT ROTATION

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.

Effects of Various Residue Management Systems on Cotton Establishment and Yield in High-Residue

A field experiment was conducted in 2007 and 2008 in central Alabama to evaluate the effects of mechanical termination cover crop, strip tillage width, and row cleaners attached either to tillage implement or planting units, on cotton population and yield. Treatments included roller (present or absent), in-row subsoiler (wide and narrow strips), and row-cleaners attached either to subsoiler, planter or both. In both years rye was terminated with glyphosate (both rolled and non-rolled rye) in mid-April, and tillage treatments were applied; cotton was planted three weeks after tillage. In 2007, generally higher cotton stands were associated with rolled rye residue (137,134 plants/ha) v/s non-rolled rye (115,641 plants/ha). On average, significantly higher cotton seed yield was found for rolled rye (4,540 kg/ha compared to non-rolled rye (4,332 kg/ha). Examining specific treatments, the highest cotton seed yield (4,933 kg/ha) was associated with rolled rye under narrow strip tillage with row cleaners attached to both subsoiler and planter. The lowest cotton yield (3,913 kg/ha) was associated with non-rolled residue, under narrow strip tillage with row cleaners present on both subsoiler and planter. In 2008, no difference was found in cotton stand for rolled (108,375 plants/ha) and non-rolled rye (107,719 plants/ha). Cotton seed yield in 2008 was higher than in 2007 due to a severe drought in Alabama during 2007. In 2008, slightly higher cotton yield was reported for non-rolled rye (5,658 kg/ha) v/s rolled rye (5,419 kg/ha). The non-rolled rye, narrow strip subsoiling and row cleaners on subsoiler produced the highest cotton yield (5,812 kg/ha) compared with the lowest (5,171 kg/ha) by rolled rye, narrow strip and row cleaners on the planter. In 2007 and 2008, the width of the tillage strip did not have a significant effect on cotton stand or cotton seed yield.

Organic Weed Control and Cover Crop Residue Integration Impacts on Weed Control, Quality, Yield and Economics in Conservation Tillage Tomato-A Case Study

The increased adoption of conservation tillage and organic weed control practices in vegetable production requires more information on the role of various cover crops in integrated weed control, tomato quality, and yield. Two conservation-till‐ age systems utilizing crimson clover and cereal rye as winter cover crops were com‐ pared to a conventional black polythene mulch system, with or without organic weed management options, for weed control, tomato yield, and profitability. All cover crops were terminated with a mechanical roller/crimper prior to planting. Or‐ ganic weed control treatments included: 1) flaming utilizing a one burner hand torch, 2) PRE application of corn gluten, 3) PRE application of corn gluten followed by flaming, or 4) intermittent hand weeding as needed. A non-treated control and a standard herbicide program were included for comparison. The herbicide program consisting of a PRE application of S-metolachlor (1.87 kg a.i./ha) followed by an ear‐ ly POST metribuzin (0.56 kg a.i. /ha) application followed by a late POST applica‐ tion of clethodim (0.28 kg a.i./ha). In general, high-residue clover and cereal rye cover crops provided substantial suppression of Palmer amaranth, large crabgrass, and yellow nutsedge. Across systems, minimum input in high-residue systems pro‐ vided the highest net returns above variable costs compared to organic herbicide treatments that are costly and provide marginal benefit.

Evaluation of Methods to Assess Termination Rates of Cover Crops Using Visual and Non-Visible Light Active Sensors

Determination of cover crop termination rate has been based exclusively on visual evaluation of color by a trained evaluator to describe the life state of the plant. However, visual color-based assessment is a subjective method and can vary from one evaluator to another. If several skilled individuals are involved in the plant evaluation process in the same field, most likely a deviation associated with the cover crop evaluation will occur due to differences in eye response to colors. To remedy this problem, two experiments over three growing seasons were conducted in Alabama to evaluate cover crop termination rates using three different evaluation methods: (1) the visual method and manual data generation, (2) a chlorophyll meter with built-in data logger, and (3) an active light sensor (Greenseeker meter) with an iPAQ to store data. The instruments have the advantage of performing these evaluations quickly and effectively, and assessments can be performed by relatively unskilled personnel in the field. A linear correlation procedure was employed to develop relationships between observed termination rates and data collected with the instruments. The goal was to establish relationships between visual determination and instrument readouts, and to use these results for developing a procedure for future cover crop senescence assessment (termination rate in percentage of cover crop). Two cover crops were evaluated: cereal rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.). Results from three years of data (2009-2011) from two sites showed that there were strong linear relationships between visual observation and data obtained from the instruments, with R2 values ranging from 0.713 to 0.945. Models were developed to predict termination rates for the two cover crops using the Greenseeker and chlorophyll meters, which are being used in agricultural research for different plant evaluation purposes.

Effect of Timing of In-Row Subsoiling on Soil Properties, Cover Crop Production, and Cotton Production

Soil compaction is often treated in the Southeastern United States by using the conservation practice of annual in-row subsoiling. It is common to in-row subsoil immediately prior to planting, however, lack of adequate rainfall in the spring of the year can prevent timely tillage and planting events. It may be helpful to conduct in-row subsoiling during winter months when rainfall is plentiful. An experiment was conducted to determine the effects of elapsed time between in-row subsoiling and planting on a highly compactable Coastal Plain soil. In-row subsoiling was conducted by two different subsoilers, a KMC and a Paratill™, during winter months when time and rainfall was more readily available. Results from this 2 year study (which is continuing) indicated that reduced bulk density, reduced cone index, and slightly increased cash crop and cover crop yields resulted from in-row subsoiling immediately prior to planting.