• Authors:
    • Correa, R.
    • Wilkins, D.
    • Siemens, M.
  • Source: Transactions of the ASAE
  • Volume: 47
  • Issue: 2
  • Year: 2004
  • Summary: Adoption of conservation tillage in the Pacific Northwest lags that of the U.S. in part due to the lack of reliable seeding equipment for planting into the high residue densities encountered in this region. To overcome this problem, a drill attachment was developed to manage heavy residue next to the furrow opening tines of hoe-type no-till drills. The U.S. patented device consists of a fingered rubber wheel, a rubber inner ring, and a spring-loaded arm that pivots about vertical and horizontal axes. The performance of the device was evaluated in terms of stand establishment and yield in Oregon and Washington. Test site locations varied significantly in the amount and condition of crop residue and were planted to a variety of different crops. As compared to the standard no-till drill without the attachment, use of the residue management wheel was found to increase the stand establishment of small seeded crops such as canola and mustard by over 40% and large seeded crops such as wheat and barley by approximately 17%. Increases in stand establishment were attributed to fewer piles of residue covering the seed row. Use of the device also significantly increased crop yield by up to 12% in 8 of the 20 trials conducted (P≤0.10). Although the residue management wheel costs $300 per unit to fabricate, using the device may be economically feasible if it results in significant improvements in both stand establishment and yield.
  • Authors:
    • Rice, C. W.
    • Kocylgit, R.
  • Source: Turkish Journal of Agriculture & Forestry
  • Volume: 28
  • Issue: 3
  • Year: 2004
  • Summary: Soil carbon (C) dynamics is an important aspect of the global C cycle. Soils can be a sink or source for atmospheric CO2 depending upon management. Tallgrass prairie and wheat (Triticum aestivum L.) are 2 dominant ecosystems in the Great Plains. This study determined the distribution of C in these 2 ecosystems. Soil C pools, plant root biomass, and aboveground plant biomass were determined at a wheat (winter wheat) and a tallgrass prairie site in northern Oklahoma from 1998 through 2001. The objectives of this study were to determine C storage and changes in soil organic matter in tallgrass prairie and wheat ecosystems under similar environmental conditions and soil characteristics. Soil C was assessed by measuring soil C pools (active, slow and recalcitrant). Mineralizable C and N (Co and No) were determined by long-term laboratory incubation, 314 days at 35 degreeC. Soil C and N content was 2 times greater in the prairie than under wheat. The greater level of Co and No occurred in prairie. Wheat had proportionally greater mineralizable C and N than did prairie, but microbial biomass was the opposite, being greater in prairie. Wheat had more dynamic C pools with a faster turnover rate than did prairie. The more dynamic C pools with a faster turnover rate in wheat was the result of the greater disturbance effects of intensive tillage practices on soil structure.
  • Authors:
    • Rice, CW
    • Doyle, G.
    • Garcia, R.
    • Litvina, IV
    • Zhou, XH
    • Schmidt, RA
    • Brandle, JR
    • Massman, WJ
    • Takle, ES
  • Source: Agricultural and Forest Meteorology
  • Volume: 124
  • Issue: 3-4
  • Year: 2004
  • Summary: We report measurements at 2 Hz of pressure fluctuations at and beneath the soil in an agricultural field with dry soil and no vegetation. The objective of our study was to examine the possible role of pressure fluctuations produced by fluctuations in ambient wind on the efflux of M at the soil surface. We observed that pressure fluctuations penetrate to 50 cm in the soil with little attenuation, thereby providing a mechanism for bulk transport of trace gases throughout the porous medium. Concurrent measurements of CO2 fluxes from the soil surface produced systematically larger values for larger values of root-mean-square pressure, pumping rate, and mean wind speed. Soil CO2 fluxes measured under conditions conducive to pressure pumping exceeded the diffusional fluxes, estimated from use of Fick's Law and concurrent vertical profiles of soil CO2, by a factor of 5-10. Extrapolation of measured fluxes to conditions uninfluenced by pressure pumping revealed that other mechanisms, such as thermal expansion of soil air caused by soil heating or flushing by evaporating water deep in the soil, may be contributing up to 60% to measured fluxes. Ambient meteorological conditions leading to flux enhancement may change on scales of hours to months, so these results underscore the need to report concurrent meteorological conditions when surface CO2 efflux measurements are made. They further suggest that fluctuations in the static pressure fields introduced by wind interactions with terrain and vegetation may lead to pressure pumping at the surface and hence large spatial inhomogeneities in soil fluxes of trace gases. Although our measurements were made at an agricultural field site and focused on CO2 efflux, the pressure pumping mechanism will be active on other sites, including forest environments, snow-covered surfaces, and fractured rocky surfaces. Furthermore, the physical processes examined apply to movement of other trace gases such as oxygen, water vapor, and methane. (C) 2004 Elsevier B.V. All rights reserved.
  • Authors:
    • Rice, C. W.
    • Claassen, M. M.
    • Nelson, R. G.
    • Williams, J. R.
  • Source: Environmental Management
  • Volume: 33
  • Issue: 1
  • Year: 2004
  • Summary: An economic analysis of wheat and grain sorghum production systems that affect carbon dioxide (CO2) emissions and sequester soil carbon (C) in metric tons (MT) is conducted. Expected net returns, changes in net C sequestered, and the value of C credits necessary to equate net returns from systems that sequester more C with those that sequester less is determined with and without adjustments for CO2 emissions from production inputs. Experiment station cropping practices, yield data, and soil C data for continuously cropped and rotated wheat and grain sorghum produced with conventional tillage and no-tillage are used. No-till has lower net returns because of somewhat lower yields and higher overall costs. Both crops produced under no-till have higher annual soil C gains than under conventional tillage. However, no-till systems have somewhat higher total atmospheric emissions of C from production inputs. The C credit values estimated in this study will equate net returns of no-tillage to conventional tillage range from $8.62 to $64.65/MT/yr when C emissions from production inputs are subtracted from soil C sequestered, and $8.59 to $60.54/MT/yr when atmospheric emissions are not considered. This indicates accounting for CO2 emissions from production inputs may not be necessary in the process to issue C credits.
  • Authors:
    • Mosier, A. R.
    • Burke, I. C.
    • Kaye, J. P.
    • Guerschman, J. P.
  • Source: Ecological Applications
  • Volume: 14
  • Issue: 4
  • Year: 2004
  • Summary: Land-use change is an important driver of soil-atmosphere gas exchange, but current greenhouse-gas budgets lack data from urban lands. Field comparisons of urban and non-urban ecosystems are required to predict the consequences of global urban-land expansion for greenhouse-gas budgets. In a rapidly urbanizing region of the U.S. Great Plains, we measured soil-atmosphere exchange of methane (CH 4) and nitrous oxide (N 2O) for one year in replicated ( n=3) urban lawn, native shortgrass steppe, dryland wheat-fallow, and flood-irrigated corn ecosystems. All soils were net sinks for atmospheric CH 4, but uptake by urban, corn, and wheat-fallow soils was half that of native grasslands (-0.300.04 g C.m -2.yr -1 [mean1 Se]). Urban (0.240.03 g N.m -2.yr -1) and corn (0.200.02 g N.m -2.yr -1) soils emitted 10 times more N 2O to the atmosphere than native grassland and wheat-fallow soils. Using remotely sensed land-cover data we calculated an upper bound for the contribution of lawns to regional soil-atmosphere gas fluxes. Urban lawns occupied 6.4% of a 1578-km 2 study region, but contribute up to 5% and 30% of the regional soil CH 4 consumption and N 2O emission, respectively, from land-use types that we sampled. Lawns that cover small portions of the landscape may contribute significantly to regional soil-atmosphere gas exchange.
  • Authors:
    • Reddy, G. B.
    • Brock, B.
    • Naderman, G.
    • Raczkowski, C. W.
  • Source: Proceedings of the 26th Southern Conservation Tillage Conference for Sustainable Agriculture 8-9 June, 2004, Raleigh, North Carolina
  • Year: 2004
  • Summary: This study reports the results of sampling soil within a field experiment at CEFS, the Cherry Farm, Goldsboro, North Carolina. The experiment tested effects of six years of conservation tillage with cover crops, contrasted with chisel plow/disk tillage without cover crops, under three crop rotations. In April, 2003 two sets of undisturbed core samples were collected from six mapped soil areas, at depth increments of 0-2 and 2-5 inches, replicated four times. One set was used for soil bulk density; the other provided soil carbon and total nitrogen contents. The study found strong and consistent inverse correlations between soil carbon content and bulk density. Under conservation tillage the surface two inches generally sustained suitable density for root activities. However, at 2-5 inches density approached or exceeded 1.6 g cm-3. Given the textures involved, this density likely would affect root growth, especially under non-ideal, wet/cool or dry/hard conditions. This would be especially important for crop establishment within this prime rooting zone. This low carbon/high-density problem was less likely for soils containing the influences of more silt with less sand. It was greater when corn, peanut and cotton were grown compared to producing soyabean or wheat/soybean with corn. This study revealed increased carbon sequestration from the conservation tillage systems used, along with increased total N content in the surface five inches of soil. Conservation tillage as practiced helped to reduce the "greenhouse effect" and lessened N leaching losses, holding more of these elements within the topsoil.
  • Authors:
    • Johnson, J. J.
    • Doerge, T. A.
    • Shanahan, J. F.
    • Vigil, M. F.
  • Source: Precision Agriculture
  • Volume: 5
  • Issue: 3
  • Year: 2004
  • Summary: The goal of this research was to determine the potential for use of site-specific management of corn hybrids and plant densities in dryland landscapes of the Great Plains by determining (1) within-field yield variation, (2) yield response of different hybrids and plant densities to variability, and (3) landscape attributes associated with yield variation. This work was conducted on three adjacent fields in eastern Colorado during the 1997, -98, and -99 seasons. Treatments consisted of a combination of two hybrids (early and late maturity) and four plant densities (24 692, 37 037, 49 382 and 61 727 plants ha -1) seeded in replicated long strips. At maturity, yield was measured with a yield-mapping combine. Nine landscape attributes including elevation, slope, soil brightness (SB) (red, green, and blue bands of image), EC a (shallow and deep readings), pH, and soil organic matter (SOM) were also assessed. An analysis of treatment yields and landscape data, to assess for spatial dependency, along with semi variance analysis, and block kriging were used to produce kriged layers (10 m grids). Linear correlation and multiple linear regression analysis were used to determine associations between kriged average yields and landscape attributes. Yield monitor data revealed considerable variability in the three fields, with average yields ranging from 5.43 to 6.39 Mg ha -1 and CVs ranging from 20% to 29%. Hybrids responded similarly to field variation while plant densities responded differentially. Economically optimum plant densities changed by around 5000 plants ha -1 between high and low-yielding field areas, producing a potential savings in seed costs of $6.25 ha -1. Variability in yield across the three landscapes was highly associated with landscape attributes, especially elevation and SB, with various combinations of landscape attributes accounting for 47%, 95%, and 76% of the spatial variability in grain yields for the 1997, -98, and -99 sites, respectively. Our results suggest site-specific management of plant densities may be feasible.
  • Authors:
    • Norman, R. J.
    • Daniel, T. C.
    • Daniels, M. B.
    • Brye, K. R.
    • Slaton, N. A.
    • Miller, D. M.
  • Source: Journal of Environmental Quality
  • Volume: 33
  • Issue: 5
  • Year: 2004
  • Summary: Knowledge of the balance between nutrient inputs and removals is required for identifying regions that possess an excess or deficit of nutrients. This assessment describes the balance between the agricultural nutrient inputs and removals for nine geographical districts within Arkansas from 1997 to 2001. The total N, P, and K inputs were summed for each district and included inorganic fertilizer and collectable nutrients excreted as poultry, turkey, dairy, and hog manures. Nutrients removed by harvested crops were summed and subtracted from total nutrient inputs to calculate the net nutrient balance. The net balances for N, P, and K were distributed across the hectarage used for row crop, hay, pasture, or combinations of these land uses. Row-crop agriculture predominates in the eastern one-third and animal agriculture predominates in the western two-thirds of Arkansas. Nutrients derived from poultry litter accounted for >92% of the total transportable manure N, P, and K. The three districts in the eastern one-third of Arkansas contained 95% of the row-crop hectarage and had net N and P balances that were near zero or negative. The six districts in the western two-thirds of Arkansas accounted for 89 to 100% of the animal populations, had positive net balances for N and P, and excess P ranged from 1 to 9 kg P ha -1 when distributed across row-crop, hay, and pasture hectarage. Transport of excess nutrients, primarily in poultry litter, outside of the districts in western Arkansas is needed to achieve a balance between soil inputs and removals of P and N.
  • Authors:
    • Sweeney, D. W.
    • Moyer, J. L.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 2
  • Year: 2004
  • Summary: With renewed interest in legumes as green manures, it is important to understand their effect on in-season N uptake of following non-legume row crops. This study assessed the effect of legumes as green manures on in-season N uptake by subsequent grain sorghum [Sorghum bicolor (L.) Moench] grown in conservation tillage systems in the eastern Great Plains. Treatments were (i) red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth) before grain sorghum vs. continuous grain sorghum, (ii) reduced or no-tillage, and (iii) fertilizer N rates. The experiment was conducted on two adjacent sites (Parson silt loam: fine, mixed thermic Mollic Albaqualf) similar in organic matter but Site 1 higher in pH, P, and K than Site 2. In-season N uptake was often statistically greater in reduced-tillage than no-tillage systems. At both sites, red clover as a previous crop resulted in about 25% greater N uptake by sorghum vs. sorghum grown continuously with no previous legume crop. Nitrogen uptake by sorghum at the boot and soft dough growth stages responded linearly to increasing N rate, but the slope was 135 kg ha(-1) during the first year for both legumes at each site, but values for red clover remained greater than those for hairy vetch in subsequent years, especially at the higher fertility site. Grain yield tended to be maximized when N uptake at the soft dough stage exceeded 100 kg ha(-1) at Site 2 but continued to increase as N uptake increased at the higher-fertility Site 1. Utilizing legumes as green manures can increase in-season N uptake by following grain sorghum crops compared with continuous sorghum in these prairie soils.
  • Authors:
    • Tiefenthaler, A. E.
    • Goldman, I. L.
    • Tracy, W. F.
    • Schaber, M. A.
  • Source: Plant Breeding Reviews: Long-term Selection: Crops, Animals, and Bacteria
  • Volume: 24
  • Issue: 2
  • Year: 2004
  • Summary: This review covers some long-term trends of the Illinois Long-term Selection Experiment and offers some perspectives on the impact of long-term selection on productivity of crops (lucerne, oats, rye, barley, winter wheat, spring wheat, soyabeans, groundnuts, sweetcorn, sweet potato, cotton, green peas, sorghum, maize, rice and potato) in the USA. Discussions on the crop productivity, variability of crop productivity and causes of increased productivity, are provided.