- Authors:
- Endale, D. M.
- Schomberg, H. H.
- Fisher, D. S.
- Jenkins, M. B.
- Sharpe, R. R.
- Cabrera, M. L.
- Source: Agronomy Journal
- Volume: 100
- Issue: 5
- Year: 2008
- Summary: Corn (Zea mays L.) producers in the southeastern United States must overcome soil and water limitations to take advantage of the expanding corn market. In this 2001 to 2005 study on a Cecil sandy loam (fine, kaolinitic, thermic Typic Kanhapludult) near Watkinsville, GA, we compared dry land corn biomass and yield under conventional tillage (CT) vs. no-tillage (NT) with ammonium nitrate or sulfate (based on availability) as conventional fertilizer (CF) vs. poultry litter (PL). In a randomized complete block split plot design with three replications, main plots were under tillage and subplots under fertilizer treatments. The cover crop was rye (Secale cereale L.). Over 5 yr, NT and PL increased grain yield by 11 and 18%, respectively, compared with CT and CF. Combined, NT and PL increased grain yield by 31% compared with conventionally tilled and fertilized corn. Similarly, soil water was 18% greater in NT than CT in the 0- to 10-cm depth. In 2 yr of measurements, dry matter of stalks and leaves and leaf area index under PL were an average of 39 and 22% greater, respectively, than under CF during reproduction. Values were 21 and 6% greater, respectively, under NT than CT but during tasseling. Analysis of 70 yr of daily rainfall records showed that supplemental irrigation is needed to meet optimal water requirement. Our results indicate that corn growers can use rainfall more efficiently, reduce yield losses to drought, and expect increased corn yields with a combination of no-tillage management and long-term use of poultry litter.
- Authors:
- Dawson, M.
- Galik, C.
- Murray, B.
- Profeta, T.
- Olander, L.
- Year: 2008
- Authors:
- Source: Journal of Environmental Quality
- Volume: 37
- Issue: 4
- Year: 2008
- Summary: It is generally recognized that soil N2O emissions can exhibit pronounced day-to-day variations; however, measurements of soil N2O flux with soil chambers typically are done only at discrete points in time. This study evaluated the impact of sampling frequency on the precision of cumulative N2O flux estimates calculated from field measurements. Automated chambers were deployed in a corn/soybean field and used to measure soil N2O fluxes every 6 h from 25 Feb. 2006 through 11 Oct. 2006. The chambers were located in two positions relative to the fertilizer bands--directly over a band or between fertilizer bands. Sampling frequency effects on cumulative N2O-N flux estimation were assessed using a jackknife technique where populations of N2O fluxes were constructed from the average daily fluxes measured in each chamber. These test populations were generated by selecting measured flux values at regular time intervals ranging from 1 to 21 d. It was observed that as sampling interval increased from 7 to 21 d, variances associated with cumulative flux estimates increased. At relatively frequent sampling intensities (i.e., once every 3 d) N2O-N flux estimates were within {+/-}10% of the expected value at both sampling positions. As the time interval between sampling was increased, the deviation in estimated cumulative N2O flux increased, such that sampling once every 21 d yielded estimates within +60% and -40% of the actual cumulative N2O flux. The variance of potential fluxes associated with the between-band positions was less than the over-band position, indicating that the underlying temporal variability impacts the efficacy of a given sampling protocol.
- Authors:
- Patton, J.
- Zhang, Q.
- Vanni, M. J.
- Renwick, W. H.
- Source: Journal of Environmental Quality
- Volume: 37
- Issue: 5
- Year: 2008
- Authors:
- Source: Turkish Journal of Agriculture and Forestry
- Volume: 32
- Year: 2008
- Summary: Public interest and awareness of the need for improving nutrient use efficiency is great, but nutrient use efficiency is easily
misunderstood. Four indices of nutrient use efficiency are reviewed and an example of different applications of the terminology show
that the same data set might be used to calculate a fertilizer N efficiency of 21% or 100%. Fertilizer N recovery efficiencies from
researcher managed experiments for major grain crops range from 46% to 65%, compared to on-farm N recovery efficiencies of
20% to 40%. Fertilizer use efficiency can be optimized by fertilizer best management practices that apply nutrients at the right rate,
time, and place. The highest nutrient use efficiency always occurs at the lower parts of the yield response curve, where fertilizer
inputs are lowest, but effectiveness of fertilizers in increasing crop yields and optimizing farmer profitability should not be sacrificed
for the sake of efficiency alone. There must be a balance between optimal nutrient use efficiency and optimal crop productivity.
- Authors:
- Stevens, W. B.
- Jabro, J. D.
- Sainju, U. M.
- Source: Journal of Environmental Quality
- Volume: 37
- Issue: 1
- Year: 2008
- Summary: Management practices can influence soil CO2 emission and C content in cropland, which can effect global warming. We examined the effects of combinations of irrigation, tillage, cropping systems, and N fertilization on soil CO2 flux, temperature, water, and C content at the 0- to 20-cm depth from May to November 2005 at two sites in the northern Great Plains. Treatments were two irrigation systems (irrigated vs. non-irrigated) and six management practices that contained tilled and no-tilled malt barley (Hordeum vulgaris L.) with 0 to 134 kg N ha-1, no-tilled pea (Pisum sativum L.), and a conservation reserve program (CRP) planting applied in Lihen sandy loam (sandy, mixed, frigid, Entic Haplustolls) in western North Dakota. In eastern Montana, treatments were no-tilled malt barley with 78 kg N ha-1, no-tilled rye (Secale cereale L.), no-tilled Austrian winter pea, no-tilled fallow, and tilled fallow applied in dryland Williams loam (fine-loamy, mixed Typic Argiborolls). Irrigation increased CO2 flux by 13% compared with non-irrigation by increasing soil water content in North Dakota. Tillage increased CO2 flux by 62 to 118% compared with no-tillage at both places. The flux was 1.5- to 2.5-fold greater with tilled than with non-tilled treatments following heavy rain or irrigation in North Dakota and 1.5- to 2.0-fold greater with crops than with fallow following substantial rain in Montana. Nitrogen fertilization increased CO2 flux by 14% compared with no N fertilization in North Dakota and cropping increased the flux by 79% compared with fallow in no-till and 0 kg N ha-1 in Montana. The CO2 flux in undisturbed CRP was similar to that in no-tilled crops. Although soil C content was not altered, management practices influenced CO2 flux within a short period due to changes in soil temperature, water, and nutrient contents. Regardless of irrigation, CO2 flux can be reduced from croplands to a level similar to that in CRP planting using no-tilled crops with or without N fertilization compared with other management practices.
- Authors:
- Reddy, K. C.
- Tazisong, I. A.
- Nyakatawa, E. Z.
- Senwo, Z. N.
- Sainju, U. M.
- Source: Agriculture, Ecosystems & Environment
- Volume: 127
- Issue: 3-4
- Year: 2008
- Summary: Disposal of poultry litter, a widely available organic manure in the southeastern USA because of a large-scale poultry industry, is a major concern because of its contamination in surface- and groundwater through N leaching and P runoff. Application of poultry litter in no-tilled intensive cropping system could increase soil C and N sequestration compared with the conventional-tilled system with inorganic N fertilization and reduce environmental contamination. We evaluated the 10-year effects of tillage, cropping systems, and N fertilizer sources on crop residue (stems + leaves) production and soil bulk density, organic C (SOC), and total N (STN) at the 0-20 cm depth in Decatur silt loam (clayey, kaolinitic, thermic, and Typic Paleudults) in northern AL, USA. Treatments were incomplete factorial combinations of three tillage practices [no-till (NT), mulch till (MT), and conventional till (CT)], two cropping systems [cotton (Gossypium hirsutum L.)-cotton-corn (Zea mays Q and rye (Secale cereale L.)/cotton-rye/cotton-corn], and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH4NO3, and 100 and 200 kg N ha(-1) from poultry litter) in randomized complete block with three replications. Rye was grown as winter cover crop and corn as residual crop without tillage and fertilization. Mean crop residue returned to the soil from 1997 to 2005 was greater in rye/cotton-rye/cotton-corn than in cotton-cotton-corn and greater with NH4NO3 than with poultry litter at 100 kg N ha(-1). While SOC and STN concentrations at 10-20 cm after 10 years were not influenced by treatments, SOC and STN contents at 0-20 cm were greater with poultry litter than with NH4NO3 in NT and CT. These resulted in a C sequestration rate of 510 kg C ha(-1) year(-1) and N sequestration rates of 41-49 kg N ha(-1) year(-1) with poultry litter compared with -120 to 147 kg C ha(-1) year(-1) and -23 to -3 kg N ha(-1) year(-1), respectively, with NH4NO3. Cropping and fertilization sequestered C at 730 kg C ha(-1) year(-1) and N at 67 kg N ha(-1) year(-1) compared with fallow and no-fertilization in NT. Tillage and cropping system did not influence SOC and STN. Long-term poultry litter application or continuous cropping can sequester C and N in the soil compared with inorganic N fertilization or fallow, thereby increasing soil quality and productivity and reducing the potentials for N leaching and greenhouse gas emission. Published by Elsevier B.V.
- Authors:
- Yu, T. -H.
- Hayes, D.
- Tokgoz, S.
- Fabiosa, J.
- Elobeid, A.
- Dong, F.
- Houghton, R. A.
- Heimlich, R.
- Searchinger, T. D.
- Source: Science
- Volume: 319
- Issue: 5867
- Year: 2008
- Summary: Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. By using a worldwide agricultural model to estimate emissions from land-use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.
- Authors:
- Asbjornsen, H.
- Schulte, L. A.
- Tyndall, J.
- Secchi, S.
- Source: Journal of Soil and Water Conservation
- Volume: 63
- Issue: 3
- Year: 2008
- Summary: from conclusion: "A conservation policy based on targeting would bring about benefits for both society and agricultural producers. With the increasing pressures being exerted on agriculture to intensify production at present, we argue that a targeted approach is timely and necessary to maintain-if not increase-the level of agroecosystem services currently provided. The targeted conservation program we outline does just this. It focuses on those portions of watersheds and/or landscapes that provide the greatest ecological benefits and more than adequately compensates farmers for taking land out of production. We further argue that a targeted approach is feasible in light of historical federal expenditures for the farm sector, and farmer compensation would more adequately reflect the quantity or quality of the conservation benefit being produced. The better targeting of resources, rather than increases in their absolute levels, is key in the provision of agroecosystem services under the current high crop price environment."
