David A. Mays

Use of Winter Annual Cover Crops to Reduce Soil Nitrate Levels

ABSTRACT The scientific community and various environmental groups have been concerned about the leaching of nitrate (NO3) to ground water from various sources including crop fields where all the applied NO3 is not utilized by the primary crop. Experiments were conducted on two soil types in Alabama to investigate the use of winter cover crops to capture NO3 remaining after the harvest of corn, cotton and soybeans. In these experiments, harvest of the primary crops was so late that cover crop growth in the fall was insufficient to immobilize significant amounts of NO3. Soil testing the following spring showed that most of the soil NO3 was in the top 30 cm (12 in) of the soil profile. A subsequent cover crop planting date experiment showed that wheat planted after September 18 and rye planted after October 2 made insufficient fall growth to immobilized significant amount of NO3. Most spring growth occurred after late February when much of the winter rainfall had already occurred. It appears that judicious selection of nitrogen fertilizer rates is a better approach to reducing NO3 leaching.

Development of natural conditions in constructed wetlands: Biological and chemical changes

Abstract The main objectives of this study were to determine the biogeochemical changes taking place in wetlands constructed on coal mine spoil, and to determine the rate at which these constructed wetlands would develop the ecological characteristics of natural wetlands. In 1992 a multicell wetland was constructed. The cells were lined with two coal mine spoil types and one topsoil. In 1993, the cells were planted with cattail ( Typha latifolia ), maidencane ( Panicum hemitomon ), pickerelweed ( Pontederia lanceolota ), and soft stem bulrush ( Scirpus validus ). Pickerelweed spread most rapidly followed by maidencane and bulrush. Cattail did not establish uniformly but spread in an irregular manner. There was no difference in plant establishment between the topsoil or the two mine spoils. The pH of the most acidic spoil increased by more than one unit after flooding. Organic matter content fluctuated in all three substrates from year to year. The concentration of the nutrient and metal elements increased after flooding. Extractable Al, Fe, and Mn increased more than other elements. The data presented here indicate that, except for organic matter accumulation, these constructed wetlands have taken on the botanical and biogeochemical characteristics of natural wetlands within 3–4 years.

Tillage and Fertilizer Management Effects on Soil-Atmospheric Exchangesof Methane and Nitrous Oxide in aCorn Production System

Land application of poultry litter (PL) presents an opportunity to improve soil productivity and disposal of poultry waste. We investigated methane (CH4) and nitrous oxide (N2O) emissions from agricultural soil receiving PL and ammonium nitrate (AN) fertilizers using surface (SA), soil incorporation (SI), and subsurface band (BA) application methods in conventional (CT) and no-tillage (NT) systems on a Decatur silt loam soil in North Alabama. Plots under CT and NT were sinks of CH4 in spring, summer, and fall. In winter, the plots had net emissions of 3.32 and 4.24 g CH4 ha-1 day-1 in CT and NT systems, respectively. Plots which received AN were net emitters of CH4 and N2O, whereas plots which received PL were net sinks of CH4. Plots which received PL using SA or SI methods were net emitters of N2O, whereas under PL using BA application, the plots were net sinks of N2O. Our study indicates that using subsurface band application of PL was the most promising environmentally sustainable poultry waste application method for reducing CH4 and N2O emissions from agricultural soil in NT and CT corn production systems on the Decatur soil in north Alabama.

NUTRIENT REQUIREMENTS OF SEVEN PLANT SPECIES WITH POTENTIAL USE IN SHORELINE EROSION CONTROL

Many factors contribute to shoreline erosion including a lack of vegetation that can survive under periods of flooding, drying, and wave action. Biotechnical methods of shoreline erosion control seem to be a low cost alternative to conventional methods. This study was an attempt, first, to evaluate the feasibility of several breakwater materials for controlling wave action; and secondly, to study the growth response of seven wetland and terrestrial plant species for potential use in biotechnical methods of shoreline erosion control. The site for the field experiment was Water F. George Reservoir located on the Chattahoochee River between Alabama and Georgia. In a greenhouse experiment, plants were evaluated at different fertility levels. Results of the field experiments indicated that wire-wrapped square straw bales, coconut fiber logs, and pine logs were effective in controlling wave action and trapping sand. Round hay bales were less effective breakwater materials. Greenhouse data indicated that cattail, soft rush, soft stem bulrush, and maidencane responded significantly to nitrogen fertilizer up to 50 kg ha−1. This rate was also optimum for bahiagrass, switchgrass, and marsh hay cordgrass. No significant increase in dry matter yield or stem count was observed by the addition of N up to 100 kg ha−1. Most of these plant species did not significantly respond to the addition of micronutrients.

Soil Carbon Dioxide Fluxes in Conventional and Conservation Tillage Corn Production Systems Receiving Poultry Litter and Inorganic Fertilizer

Soil management practices can alter the natural balance at the soil-plant-atmosphere ecosystem interface, which can significantly affect the environment. This study compared CO2 fluxes in conventional tillage (CT) and no-tillage (NT) corn (Zea mays L.) production systems receiving poultry litter (PL) and ammonium nitrate (AN) fertilizers on a Decatur silt loam soil in the Tennessee Valley region of North Alabama from Spring 2008 to Fall 2009. Soil CO2 flux in CT plots (9.5 kg CO2 ha−1 day−1) was significantly greater than that in NT plots (4.9 kg CO2 ha−1 day−1 in summer. Soil CO2 fluxes were lowest in fall where CT plots had a mean soil CO2 emission of 0.8 kg CO2 ha−1 day−1, while plots under NT and grass fallow system were sinks of CO2 with fluxes −0.6 and −1.0 kg CO2 ha−1 day−1, respectively. Mean soil CO2 flux averaged over seasons in NT plots was 36% lower than that in CT plots. Grass fallow plots were net sinks of CO2 with a mean CO2 flux of −0.4 kg CO2 ha−1 day−1. Our study showed that application of PL or AN fertilizer in NT systems can significantly reduce soil CO2 emissions compared to CT systems in corn production.

Nitrogen and phosphorus transport in runoff from compost berms on a simulated military training landscape

Compost mulches have potential to significantly offset on- and off-site environmental impacts resulting from mechanical soil disturbances and training manoeuvres on military training ranges. N and P transport was investigated in runoff from compost mulch berms made from various organic waste materials in combination with each other and with soil on a simulated military training landscape in north Alabama in 2007 and 2008. Berms were constructed using composted municipal yard waste (YW), wood chips (WC), pine bark fines (PB), and soil (SL) mixed in eight different proportions. Berms made from 100% soil which had a cumulative runoff PO4-P content of 12 mg L-1 posed the greatest threat of negatively impacting the environment from inorganic P transport. Using compost mulch material with 40% soil to build berms reduced the potential for yard waste and wood chips to cause off-site negative environmental impacts from total dissolved solids, N, and P transport. Berms made from 100% pine bark fines which had cumulative runoff values of 760, 9, 22 and 5 mg L -1, respectively, of TDS, NH4-N, NO3-N, and PO 4-P had the least potential to cause negative off-site environmental impact. To prevent negative impacts of nutrient transport in runoff from berms on training landscapes, the sites need to be well buffered to hydrologically isolate them from adjoining ecosystems.

Runoff and Sediment Transport from Compost Mulch Berms on a Simulated Military Training Landscape

Soil erosion and runoff due to mechanical disturbances on military training ranges can cause problems such as land degradation and environmental pollution of downstream ecosystems. This paper discusses runoff and sediment transport from compost mulch berms on a simulated military training landscape. The berms were constructed using mixtures of municipal yard waste (YW), wood chips (WC), pine bark fines (PB), and sub-soil (SL) in eight different proportions at Hazel Green, North Alabama, in Fall 2006. Berms made from 100% soil, which had over 140 000 L ha−1 of runoff and 13.3 kg ha−1 of sediment transport over the study period, had the greatest risk of causing off-site negative environmental effects. Berms made from 100% PB and 100% WC or combinations of compost materials without soil had the lowest risk of causing environmental pollution from runoff and sediment transport. Compared to soil, compost mulches can significantly reduce negative environmental effects to downstream ecosystems when used for berm construction on military training ranges. However, measures to minimize transport of C and N in runoff sediment, such as planting grass cover crops, need to be evaluated to make the technology more environmentally sustainable.

Influence of split‐applied nitrogen on grain yield and protein content in ten grain sorghum culti‐vars 1

Abstract More information on the response of newly developed or introduced grain sorghum cultivare to split‐applied nitrogen (N) in semi‐arid rainfed agriculture is needed. Therefore, the influence of four split‐applied N schedules (100/0, 66/34, 50/50, and 34/66) on six American (SC 283, SC 274, SC 669, B 66181, SC 33, and RTam 428), and four West African (CSm 63, 1S 6704c, 1S 7173c, and 1S 7419c) grain sorghum cultivars was evaluated. The split‐applied N significantly increased grain yield and percent protein in grain sorghum over a one‐time application of N. The increase in yield and protein content varied among varieties and schedules of N application. Varieties SC 574, RTam 428, and Csm 63 at split‐applied schedules of 66/34, 50/50, and 34/66, respectively, gave the highest yield over one‐time application of N. Similar differences in percent protein in grain among cultivars due to split‐applied N were observed.