• Authors:
    • McLaughlin, N. B.
    • Calder, W.
    • Welacky, T. W.
    • Tan, C. S.
    • Reynolds, W. D.
    • Drury, C. F.
  • Source: Soil Science Society of America Journal
  • Volume: 70
  • Issue: 2
  • Year: 2006
  • Summary: Innovative management practices are required to increase the efficiency of N fertilizer usage and to reduce nitrous oxide (N2O) and carbon dioxide (CO2) emissions from agricultural soils. The objectives of this study were to evaluate the feasibility of using conservation tillage and N fertilizer placement depth to reduce N2O and CO2 emissions associated with corn (Zea mays L.) production on clay loam soils in Eastern Canada. A 3-yr field study was established on a wheat (Triticum aestivum L.)-corn-soybean [Glycine max (L.) Merr.] rotation with each phase of the rotation present every year. Investigations were focused on the corn phase of the rotation. The tillage treatments following winter wheat included fall moldboard plow tillage (15 cm depth), fall zone-tillage (21 cm width, 15 cm depth), and no-tillage. The N placement treatments were "shallow" placement of sidedress N (2-cm depth) and "deep" placement of sidedress N (10-cm depth). Nitrous oxide emissions were measured 53 times and CO2 emissions were measured 43 times over three growing seasons using field-based sampling chambers. There was a significant tillage and N placement interaction on N2O emissions. Averaged over all three tillage systems and site-years, N2O emissions from shallow N placement (2.83 kg N ha-1 yr-1) were 26% lower than deep N placement (3.83 kg N ha-1 yr-1). The N2O emissions were similar among the tillage treatments when N was placed in the soil at a shallow depth. However, when N was placed deeper in the soil (10 cm), the 3-yr average N2O emissions from zone-tillage (2.98 kg N ha-1 yr-1) were 20% lower than from no-tillage (3.71 kg N ha-1 yr-1) and 38% lower than those from moldboard plow tillage (4.81 kg N ha-1 yr-1). Tillage type and N placement depth did not affect CO2 emissions (overall average = 5.80 Mg C ha-1 yr-1). Hence, zone-tillage and shallow N placement depth reduced N2O emissions without affecting CO2 emissions.
  • Authors:
    • Caswell, M.
    • Fernandez-Cornejo, J.
  • Source: Economic Information Bulletin Number 11
  • Volume: 11
  • Year: 2006
  • Authors:
    • Robertson, G. P.
    • Parr, S.
    • Loecke, T. D.
    • Grandy, A. S.
  • Source: Journal of Environmental Quality
  • Volume: 35
  • Issue: 4
  • Year: 2006
  • Summary: No-till cropping can increase soil C stocks and aggregation but patterns of long-term changes in N2O emissions, soil N availability, and crop yields still need to be resolved. We measured soil C accumulation, aggregation, soil water, N2O emissions, soil inorganic N, and crop yields in till and no-till corn-soybean-wheat rotations between 1989 and 2002 in southwestern Michigan and investigated whether tillage effects varied over time or by crop. Mean annual NO3- concentrations in no-till were significantly less than in conventional till in three of six corn years and during one year of wheat production. Yields were similar in each system for all 14 years but three, during which yields were higher in no-till, indicating that lower soil NO3- concentrations did not result in lower yields. Carbon accumulated in no-till soils at a rate of 26 g C m-2 yr-1 over 12 years at the 0- to 5-cm soil depth. Average nitrous oxide emissions were similar in till (3.27 {+/-} 0.52 g N ha d-1) and no-till (3.63 {+/-} 0.53 g N ha d-1) systems and were sufficient to offset 56 to 61% of the reduction in CO2 equivalents associated with no-till C sequestration. After controlling for rotation and environmental effects by normalizing treatment differences between till and no-till systems we found no significant trends in soil N, N2O emissions, or yields through time. In our sandy loam soils, no-till cropping enhances C storage, aggregation, and associated environmental processes with no significant ecological or yield tradeoffs.
  • Authors:
    • Tiffany, D.
    • Polasky, S.
    • Tilman, David
    • Nelson, E.
    • Hill, J.
  • Source: Proceedings of the National Academy of Sciences of the United States of America
  • Volume: 103
  • Issue: 30
  • Year: 2006
  • Summary: Negative environmental consequences of fossil fuels and concerns about petroleum supplies have spurred the search for renewable transportation biofuels. To be a viable alternative, a biofuel should provide a net energy gain, have environmental benefits, be economically competitive, and be producible in large quantities without reducing food supplies. We use these criteria to evaluate, through life-cycle accounting, ethanol from corn grain and biodiesel from soybeans. Ethanol yields 25% more energy than the energy invested in its production, whereas biodiesel yields 93% more. Compared with ethanol, biodiesel releases just 1.0%, 8.3%, and 13% of the agricultural nitrogen, phosphorus, and pesticide pollutants, respectively, per net energy gain. Relative to the fossil fuels they displace, greenhouse gas emissions are reduced 12% by the production and combustion of ethanol and 41% by biodiesel. Biodiesel also releases less air pollutants per net energy gain than ethanol. These advantages of biodiesel over ethanol come from lower agricultural inputs and more eficient conversion of feedstocks to fuel. Neither biofuel can replace much petroleum without impacting food supplies. Even dedicating all U.S. corn and soybean production to biofuels would meet only 12% of gasoline demand and 6% of diesel demand. Until recent increases in petroleum prices, high production costs made biofuels unprofitable without subsidies. Biodiesel provides suficient environmental advantages to merit subsidy. Transportation biofuels such as synfuel hydrocarbons or cellulosic ethanol, if produced from low-input biomass grown on agriculturally marginal land or from waste biomass, could provide much greater supplies and environmental benefits than food-based biofuels.
  • Authors:
    • Al-Kaisi, M.
  • Source: Integrated Crop Management
  • Volume: IC-496
  • Issue: 11
  • Year: 2006
  • Authors:
    • Hunt, P. G.
    • Novak, J. M.
    • Frederick, J. R.
    • Bauer, P. J.
  • Source: Soil & Tillage Research
  • Volume: 90
  • Issue: 1-2
  • Year: 2006
  • Summary: Tillage affects the ability of coarse-textured soils of the southeastern USA to sequester C. Our objectives were to compare tillage methods for soil CO2 flux, and determine if chemical or physical properties after 25 years of conventional or conservation tillage correlated with flux rates. Data were collected for several weeks during June and July in 2003, October and November in 2003, and April to July in 2004 from a tillage study established in 1978 on a Norfolk loamy sand (fine-loamy, kaolinitic, thermic Typic Kandiudults). Conventional tillage consisted of disking to a depth of approximately 15 cm followed by smoothing with an S-tined harrow equipped with rolling baskets. Conservation tillage consisted of direct seeding into surface residues. Flux rates in conservation tillage averaged 0.84 g CO2 m-2 h-1 in Summer 2003, 0.36 g CO2 m-2 h-1 in Fall 2003, 0.46 g CO2 m-2 h-1 in Spring 2004, and 0.86 g CO2 m-2 h-1 in Summer 2004. Flux rates from conventional tillage were greater for most measurement times. Conversely, water content of the surface soil layer (6.5 cm) was almost always higher with conservation tillage. Soil CO2 flux was highly correlated with soil water content only in conventional tillage. In conservation tillage, no significant correlations occurred between soil CO2 flux and soil N, C, C:N ratio, pH, bulk density, sand fraction, or clay fraction of the surface 7.5 cm. In conventional tillage, sand fraction was positively correlated, while bulk density and clay fraction were negatively correlated with soil CO2 flux rate, but only when the soil was moist. Long-term conservation tillage management resulted in more uniform within- and across-season soil CO2 flux rates that were less affected by precipitation events.
  • Authors:
    • Marchetti, M.
    • Vitorino, A.
    • Souza, L.
    • Brandt, E.
  • Source: CIENCIA E AGROTECNOLOGIA
  • Volume: 30
  • Issue: 5
  • Year: 2006
  • Summary: The effects of crop rotation on the performance of soyabean were studied in Dourados, Mato Grosso do Sul, Brazil, during 1998, 1999 and 2000. The treatments were: maize/vetch/maize/vetch/soyabean, cotton/oat/cotton/sorghum/soyabean, soyabean/wheat/soyabean/maize/millet/soyabean, maize/grazing turnip/maize/sorghum/soyabean, maize/oat/maize/bean/millet/soyabean, rice/grazing turnip/rice/oat/soyabean, rice/sorghum/rice/bean/millet/soyabean, cotton/wheat/cotton/wheat/soyabean, and cotton/grazing turnip/cotton/oat/soyabean. Dry matter of aerial parts at the full flowering stage, plant height, first pod insertion, number of pods per plant, productivity and 1000-grain mass were evaluated. The rotation system had no significant effects on plant height, first pod insertion, and number of pods per plant. The highest grain yields were obtained under rice/sorghum/rice/bean/millet/soyabean and soyabean/wheat/soyabean/maize/millet/soyabean.
  • Authors:
    • Hons, F.
    • Dou, F.
  • Source: Soil Science Society of America Journal
  • Volume: 70
  • Issue: 6
  • Year: 2006
  • Summary: Management practices that alter plant residue production and distribution influence SOC (soil organic carbon) dynamics. The objectives of this study were to investigate the impacts of tillage, cropping system, and N fertilizer application on SOC and soil N pools through physical fractionation of a central Texas soil after 20 years. Nitrogen fertilizer application and no-tillage (NT) significantly increased wheat ( Triticum aestivum) straw yield. Compared with conventional tillage (CT), SOC under NT in surface (0-5 cm) samples was 38, 69, and 68% greater for continuous wheat (CW), wheat-soyabean ( Glycine max)-sorghum ( Sorghum bicolor) rotation (SWS), and double-cropped wheat-soyabean (WS), respectively. The greatest SOC was observed in WS under NT with N fertilizer application, and the lowest occurred in CW under CT without N. Increased cropping intensity increased SOC compared with monoculture. Nitrogen fertilizer application only significantly increased SOC sequestration under NT. No-tillage increased SOC concentration in all physical size fractions compared with CT. Increased cropping intensity and N fertilizer application significantly increased SOC sequestration in most size fractions only under NT. Intraparticulate organic matter C (IPOM-C) was proportionally more affected by tillage than total SOC, indicating that this fraction was more sensitive to management. Carbon concentrations in all size fractions were significantly correlated with each other as well as SOC. Our results indicated that NT associated with enhanced cropping intensity and N fertilizer application sequestered greater SOC and soil total N.
  • Authors:
    • Gallagher, L.
    • Armentrout, D.
    • Kratochvil, R.
    • Sardanelli, S.
    • Everts, K.
  • Source: Plant Disease
  • Volume: 90
  • Issue: 4
  • Year: 2006
  • Summary: Experiments using soil-incorporated cover crops and amendments of poultry litter (PL) and PL compost to suppress root-knot (RKN) and root-lesion nematodes were conducted in response to increasing nematode populations in Maryland's potato production areas. Identical experiments were established in microplots infested with Meloidogyne incognita or Pratylenchus penetrans. Treatments consisted of 12 3-year rotational sequences comprising potato (year 1) and cucumber (year 2) followed by a moderately RKN-resistant or susceptible soyabean cultivar, castor bean, grain sorghum, or sorghum sudangrass; PL or PL compost were amended to some of the RKN-susceptible soyabean and sorghum sudangrass plots. In the third year of the rotation, potato followed by soyabean was planted in all 12 treatments. The RKN-resistant soyabean, castor bean, sorghum sudangrass, and fallow or tillage decreased the populations of M. incognita compared with microplots where RKN-susceptible soyabean had been grown. However, RKN populations quickly recovered. Root-lesion nematode was reduced in the spring of 2001 following application of high rates of PL and PL compost in 2000. In the fall of 2001, sorghum sudangrass alone or in combination with PL or PL compost, grain sorghum, or fallow or tillage reduced root-lesion nematodes compared with either soyabean cultivar. No treatment affected root-lesion nematode the following year. The use of cover crops and PL compost is an effective method to reduce nematode populations only if successively incorporated into rotational cropping sequences.
  • Authors:
    • Gamero, C.
    • Rodrigues, J.
  • Source: Energia na Agricultura
  • Volume: 21
  • Issue: 4
  • Year: 2006
  • Summary: The present study aimed to evaluate the energy demand and the effective field capacity in different soil management systems, and three kinds of vegetal covering for soyabean cultivation. The experiment was carried out at the Lageado Experimental Farm, School of Agronomical Sciences, UNESP, Botucatu, SP, Brazil. The experimental area soil was classified as Red Dystroferric Nitosol. The experiment consisted of nine treatments combining three soil management systems (conventional, reduced and no-tillage) and three vegetal covering (black oats, sorghum and spontaneous vegetation). The experimental design was in randomized blocks, 3*3 factorial scheme with 4 replications, using Tukey's test at 5% to compare means. The soil management systems presented significant differences in the effective field capacity, fuel consumption per hour and operational consumption; the no-tillage system presented the best results, regardless of soil vegetal covering.