Thomas R. Way

Conservation tillage issues: Cover crop-based organic rotational no-till grain production in the mid-Atlantic region, USA

Organic producers in the mid-Atlantic region of the USA are interested in reducing tillage, labor and time requirements for grain production. Cover crop-based, organic rotational no-till grain production is one approach to accomplish these goals. This approach is becoming more viable with advancements in a system for planting crops into cover crop residue flattened by a roller–crimper. However, inability to consistently control weeds, particularly perennial weeds, is a major constraint. Cover crop biomass can be increased by manipulating seeding rate, timing of planting and fertility to achieve levels(>8000kgha �1 ) necessary for suppressing summerannual weeds. However, while cover crops are multi-functional tools, when enhancing performance for a given function there are trade-off with other functions. While cover crop management is required for optimal system performance, integration into a crop rotation becomes a critical challenge to the overall success of the production system. Further, high levels of cover crop biomass can constrain crop establishment by reducing optimal seed placement, creating suitable habitat for seed- and seedling-feeding herbivores, and impeding placement of supplemental fertilizers. Multi-institutional and -disciplinary teams have been working in the mid-Atlantic region to address system constraints and management trade-off challenges. Here, we report on past and current research on cover crop-based organic rotational no-till grain production conducted in the mid-Atlantic region.

Broiler litter application method and runoff timing effects on nutrient and Escherichia coli losses from tall fescue pasture.

The inability to incorporate manure into permanent pasture leads to the concentration of nutrients near the soil surface with the potential to be transported off site by runoff water. In this study, we used rainfall simulations to examine the effect of broiler chicken (Gallus gallus domesticus) litter application method and the runoff timing on nutrient and E. coli losses from tall fescue (Festuca arundinacea Schreb.) pasture on a Hartsells sandy loam soil (fine-loamy, siliceous, subactive, thermic Typic Hapludults)) in Crossville, AL. Treatments included two methods of litter application (surface broadcast and subsurface banding), commercial fertilizer, and control. Litter was applied at a rate of 8.97 Mg ha(-1). Treatments were assigned to 48 plots with four blocks (12 plots each) arranged in a randomized complete block design to include three replications in each block. Simulated rainfall was applied to treatments as follows: Day 1, block 1 (runoff 1); Day 8, block 2 (runoff 2); Day 15, block 3 (runoff 3); and Day 22, block 4 (runoff 4). Total phosphorus (TP), inorganic N, and Escherichia coli concentrations in runoff from broadcast litter application were all significantly greater than from subsurface litter banding. The TP losses from broadcast litter applications averaged 6.8 times greater than those from subsurface litter applications. About 81% of the runoff TP was in the form of dissolved reactive phosphorus (DRP) for both litter-application methods. The average losses of NO(3)-N and total suspended solids (TSS) from subsurface banding plots were 160 g ha(-1) and 22 kg ha(-1) compared to 445 g ha(-1) and 69 kg ha(-1) for the broadcast method, respectively. Increasing the time between litter application and the first runoff event helped decrease nutrient and E. coli losses from surface broadcast litter, but those losses generally remained significantly greater than controls and subsurface banded, regardless of runoff timing. This study shows that subsurface litter banding into perennial grassland can substantially reduce nutrient and pathogen losses in runoff compared to the traditional surface-broadcast practice.

SOIL STRESSES UNDER A TRACTOR TIRE AT VARIOUS LOADS AND INFLATION PRESSURES

Abstract Soil stresses were measured under a 18.4R38 R-1 radial-ply tractor tire, operated at two levels each of dynamic load and inflation pressure. Stress state transducers were placed at two depths beneath the centerline of the path of the tractor tire in two different compaction profiles in each of two soils. Peak soil stresses and soil bulk density increased with increases in both dynamic load and inflation pressure.

The effects of reduced inflation pressure on soil-tire interface stresses and soil strength

Abstract Inflation pressures as low as 41 kPa have been recommended by agricultural tire manufacturers for minimizing an oscillatory vibration problem, commonly called “power hop”. Other benefits of these lower inflation pressures might include decreased soil-tire interface pressures, increased tire performance, and decreased soil compaction. Measurements of soil-tire interface stresses were made at four positions on the lugs and a three positions between lugs on an 18.4-R38 R-1 radial factor tire operated at four combinations of dynamic load and inflation pressure. These measurements showed that as inflation pressure increased, the soil-tire interface stresses near the center of the tire increased, while the stresses near the edge of the tire did not change. The increased stresses near the center of the tire were also transferred to the soil as a compaction increase sensed with the cone penetrometer. “Correctly” inflated tires (i.e. lower inflation pressures) also improved net traction and tractive efficiency.

Inflation Pressure and Dynamic Load Effects on Soil Deformation and Soil-tire Interface Stresses

An 18.4 R38 R-1 radial tractor tire at inflation pressures of 41 and 124 kPa and at dynamic loads of 13.1 and 25.3 kN was evaluated to determine the effects of the new load-inflation pressure tables on soil deformation and contact stresses. Measurements of rut width and deformed rut area were conducted with a profile meter. Soil-tire interface stress measurements were also made to determine stresses occurring between the tire and the soil and to determine the tire footprint length. Inflation pressure and dynamic load effects were found on rut width, contact length, and contact area. Dynamic load effects were also found on deformed rut area. Increased levels of soil-tire interface stress was found near the center of the tire when inflation pressure or dynamic load was increased.

Effect of direct incorporation of poultry litter on phosphorus leaching from coastal plain soils

Management of poultry litter on the Delmarva Peninsula is critical to reducing phosphorus losses to the Chesapeake Bay. New poultry litter incorporation technologies have shown promise at reducing phosphorus losses, but their effectiveness has not been tested in this environmentally sensitive region. This study evaluates subsurface leaching losses of three litter application methods, including surface broadcast, surface broadcast with disking, and subsurface litter incorporation with a novel litter incorporator developed by the USDA Agricultural Research Service. Cube-shaped soil lysimeters (61 × 61 × 61 cm [24 × 24 × 24 in]) were extracted from high phosphorus (P) (Mehlich-3 P is greater than 500 mg kg−1) agricultural soils on the University of Maryland Eastern Shore Research Farm near Princess Anne, Maryland, and were subjected to two rainfall simulation events that were separated by 11 semiweekly soaking-type irrigation events. The average cumulative total phosphorus loss was highest for the subsurface litter incorporation method (0.48 kg ha−1 [0.43 lb ac−1]) and was lowest for the no litter control (0.19 kg ha−1 [0.17 lb ac−1]). Particulate P loss among manure treatments ranged from 58% to 64% of total P loss. Total phosphorus losses were strongly correlated to total phosphorus concentration in the leachate (coefficient of determination [r2] ≥ 0.84), indicating availability of P in applied litter to be the primary control of P in leachate. Soil properties also impacted P leaching losses, with the soils possessing a higher sand content and having a shallower depth to the sandy subsoil, yielding higher cumulative total P losses (0.64 kg ha−1 [0.57 lb ac−1]). Although the subsurface litter incorporator increased total P leaching losses, a concern on the Delmarva Peninsula, opportunity exists to modify the subsurface incorporator design using zone tillage, potentially reducing the leaching losses.

Water-quality effects of a mechanized subsurface-banding technique for applying poultry litter to perennial grassland

Poultry litter is known to be an excellent organic fertilizer, but the common practice of spreading litter on the surface of pastures has raised serious water-quality concerns and may limit potential benefits of litter applications. Because surface-applied litter is completely exposed to the atmosphere, runoff can transport nutrients into nearby streams and lakes, and much of the ammonium nitrogen volatilizes before it can enter the soil. Our previous research showed that a manual knifing technique to apply dry litter under a perennial pasture surface effectively prevented about 90% of nutrient loss with runoff from surface-applied litter, and tended to increase forage yield. However, this technique (known as subsurface banding) cannot become a practical management option for producers until it is mechanized. To begin that process, we tested an experimental single-shank, tractor-drawn implement designed to apply poultry litter in subsurface bands. Our objective was to compare this mechanized subsurface-banding method against conventional surface application to determine effects on nutrient loss with runoff from a perennial grassland treated with dry poultry litter. Early in the growing season, broiler litter was applied (6.7 dry-weight Mgha(-1)) to each plot (except three control plots) using one of two application methods: surface broadcast manually or subsurface banded using the tractor-drawn implement. Simulated rainfall (5cmh(-1)) generated 20min of runoff from each plot for volume and analytical measurements. Results showed that subsurface-banded litter increased forage yield while decreasing nutrient (e.g. N and P) loss in runoff by at least 90% compared to surface-broadcast litter.

Tire lug height effect on soil stresses and bulk density

Soil stresses and increases in soil bulk density were measured beneath the centerline of one new 18.4R38 radial-ply R-1 tractor tire and two similar tires with lug heights of 55% and 31% of the new tire lug height. Each tire was operated with an inflation pressure of 110 kPa, a dynamic load of 25.0 kN and 10% slip. Soil stress state transducers (SSTs) measured the stresses at three depths in both a hardpan soil profile and a uniform soil profile, each in a sandy loam and a clay loam soil. The initial depths of the SSTs ranged from 164 to 288 mm. Analysis of the original soil stress data showed that lug height did not significantly affect the peak octahedral normal stress or its corresponding octahedral shear stress. When outliers were removed from the peak stress data, however, lug height significantly affected the octahedral normal stress in the sandy loam soil. In the uniform profile of the sandy loam and in the hardpan profile of the clay loam, the new tire generated the greatest bulk density increase, which was significantly greater than the bulk density increase caused by the 55% tire. In the sandy loam with the hardpan profile, the 55% lug height tire generated a significantly greater bulk density increase than either the new or 31% tire.

THREE-DIRECTIONAL CONTACT STRESS DISTRIBUTIONS FOR A PNEUMATIC TRACTOR TIRE IN SOFT SOIL

Three-directional contact stresses were investigated at three locations on a lug of a pneumatic tractor tire in a completely soft rotary-tilled soil overlying a hardpan about 250 mm below the surface. The 12.4R28 pneumatic tractor drive tire was operated at two dynamic loads and two inflation pressures at 20% slip. Three transducers were embedded in the lug face near the tire centerline, approximately the center of the lug, and near the outside edge of the lug. The general trend of stress distributions reflected the effect of tire inflation pressure more than dynamic load in this experiment. Increased dynamic load increased the levels of stresses. The maximum normal stress occurred near the tire centerline at high inflation pressure. The maximum tangential stress occurred near the tire centerline and decreased as the position moved from the tire centerline to the edge of the tire. At the high inflation pressure, the maximum lateral stress was concentrated near the bottom center position for each transducer.

Impact of Tillage and Fertilizer Application Method on Gas Emissions in a Corn Cropping System

Abstract Tillage and fertilization practices used in row crop production are thought to alter greenhouse gas emissions from soil. This study was conducted to determine the impact of fertilizer sources, land management practices, and fertilizer placement methods on greenhouse gas (CO 2 , CH 4 , and N 2 O) emissions. A new prototype implement developed for applying poultry litter in subsurface bands in the soil was used in this study. The field site was located at the Sand Mountain Research and Extension Center in the Appalachian Plateau region of northeast Alabama, USA, on a Hartsells fine sandy loam (fine-loamy, siliceous, subactive, thermic Typic Hapludults). Measurements of carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) emissions followed GRACEnet (greenhouse gas reduction through agricultural carbon enhancement network) protocols to assess the effects of different tillage (conventional vs. no-tillage) and fertilizer placement (subsurface banding vs. surface application) practices in a corn ( Zea mays L.) cropping system. Fertilizer sources were urea-ammonium nitrate (UAN), ammonium nitrate (AN) and poultry litter (M) applied at a rate of 170 kg ha −1 of available N. Banding of fertilizer resulted in the greatest concentration of gaseous loss (CO 2 and N 2 O) compared to surface applications of fertilizer. Fertilizer banding increased CO2 and N2O loss on various sampling days throughout the season with poultry litter banding emitting more gas than UAN banding. Conventional tillage practices also resulted in a higher concentration of CO 2 and N 2 O loss when evaluating tillage by sampling day. Throughout the course of this study, CH 4 flux was not affected by tillage, fertilizer source, or fertilizer placement method. These results suggest that poultry litter use and banding practices have the potential to increase greenhouse gas emissions.