Browsing by Author "Balkcom, Kipling S."

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  • Carbon and nitrogen mineralization and persistence of organic residues under conservation and conventional tillage
    Mulvaney, Michael J.; Wood, C. Wesley; Balkcom, Kipling S.; Shannon, D. A.; Kemble, J. M. (Madison, WI: American Society of Agronomy, 2010)
    Combining high biomass cover crops with in situ organic mulches may achieve adequate weed control for no-till production, but the persistence and nutrient release rates from cover crops and mulches is unknown. This article describes carbon and nitrogen mineralization rates from three organic mulches (mimosa (Albizia julibrissin Durazz.), lespedeza (Lespedeza cuneata (Dum. Cours.) G. Don)), and oat (Avena sativa L.) straw) and one summer cover crop (soybean (Glycine max (L.) Merr.)). The experiment used litterbag methodology on a Wickham fine sandy loam in Tallassee, AL, USA. Litterbags containing the equivalent of 6.7 Mg ha-1 were placed on the soil surface (to represent conservation tillage) or buried at 10 cm depth (to represent conventional tillage) in October 2007 and retrieved periodically up to a year later. Soybean residue mineralized N at similar rates regardless of placement, but more N was potentially available from surface-placed residues than buried residues, showing that surface placed residues may act as a slow-release N fertilizer. Likewise, C was mineralized more rapidly from buried residues than surface-placed residues. The results quantify the increased amount of C that is sequestered when these residues are used in conservation tillage compared to conventional tillage. This research implies that the use of biomass cover crops and in situ organic mulches could have a measurable impact on carbon retention rates, which will reduce the amount of carbon being released into the atmosphere.
  • Effects of high biomass cover crops and organic mulches on soil properties and collard yield three years after conversion to no-till
    Mulvaney, Michael J.; Wood, C. Wesley; Balkcom, Kipling S.; Shannon, Dennis; Kemble, Joseph (ASA-CSSA-SSSA, 2010)
    Organic producers interested in the adoption of conservation tillage continue to face considerable challenges, particularly with regard to weed control. Previous work demonstrated that high biomass cover crops in conjunction with organic mulches can provide adequate weed control in a no-till system, but the effects of high biomass cover crops and mulches on soil quality during no-till vegetable production has not been investigated. The objective of this study was to determine the effects of organic mulches and forage soybean (Glycine max (L.) Merr. cv. Derry) as a summer cover crop on soil organic carbon (SOC), carbon (C) mineralization, total soil nitrogen (N), aggregate stability, and yield in a no-till system without the use of herbicides during limited-input fall collard (Brassica oleracea L. cv. Champion) production in central eastern Alabama. All treatments, including controls, increased SOC in the 0-5 cm soil depth, indicating that high biomass no-till was more influential on SOC accumulation than the inclusion of summer cover crops or organic mulches. Treatments did not affect collard yield, which averaged 17,863 kg ha-1 yr-1. Mulches applied at 6.7 Mg ha-1 yr-1 did not mineralize nutrients in sufficient quantities to meet collard demands after three years, although the crop appeared healthy. This research highlights the need for careful nutrient management under limited-input no-till vegetable production.
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    Evaluation of Two Irrigation Scheduling Methods and Nitrogen Rates on Corn Production in Alabama
    Da Cunha Leme Filho, Jose Franco; Ortiz, Brenda V.; Balkcom, Kipling S.; Damianidis, Damianos; Knappenberger, Thorsten J.; Dougherty, Mark (Hindawi, 2020-09-15)
    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.
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    Impact of No-Tillage and Conventional Tillage Systems on Soil Microbial Communities
    Mathew, Reji P.; Feng, Yucheng; Githinji, Leonard; Ankumah, Ramble; Balkcom, Kipling S. (2012)
    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.
  • Nitrogen and Carbon Mineralization from Peanut Residues under Conservation and Conventional Tillage at Two Locations
    Mulvaney, Michael J.; Wood, C. Wesley; Balkcom, Kipling S.; Meso, Bernard (2011)
    Residue management is an important aspect of crop production systems. Availability of plant residue nitrogen (N) to succeeding crops is dependent on N mineralization rates and therefore on rates of N release during decomposition. Much of the information available on N release rates from peanut (Arachis hypogaea L.) residue is based on controlled-environment studies. The objective of this study was to assess N release rates in the field from the residues of three peanut varieties (NC V-11, GA 02-C and ANorden) at two placements (surface and 10 cm deep) and two locations (Upper Coastal Plain Experiment Station in Edgecombe County, North Carolina and Wiregrass Experiment Station in Henry County, Alabama), representing the northern and southern limits of commercial peanut production in the US. Litterbags containing the equivalent of 3.5 Mg ha-1 were placed in a completely randomized design, blocked by location, with four replications and retrieved periodically up to 335 days after application. Results showed a statistical difference for placement by time (within location) interactions and fit single or double exponential decay models. Buried residues mineralized N at higher rates than surface residues in North Carolina during the initial 50 days of decomposition. After the initial rapid phase of decomposition, there was no difference in rates of N release at either experiment station. Apart from time, no treatment differences were found at the Wiregrass Experiment Station. The data show that N is released quickly after peanut harvest if residue is left in the field.