• 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:
    • Spera, S.
    • Lhamby, J.
    • Santos, H.
  • Source: Ciencia Rural
  • Volume: 36
  • Issue: 1
  • Year: 2006
  • Summary: A 6-year (1997/98-2002/03) study was undertaken in Passo Fundo, Rio Grande do Sul, Brazil, to assess the effects of soil tillage systems and crop rotation systems on soyabean grain yield and its components. The treatments comprised 4 soil tillage systems: (1) no-tillage, (2) minimum tillage in winter and no-tillage in summer, (3) conventional tillage with a disc plough in winter and no-tillage in summer, and (4) tillage using a mouldboard plough in winter and no-tillage in summer; and 3 crop rotation systems (I) wheat/soyabean, (II) wheat/soyabean and common vetch [ Vicia sativa]/maize or sorghum, and (III) wheat/soyabean, common vetch/maize or sorghum and white oats/soyabean. The yield and weight of 1000 kernels of soyabean grown under no-tillage and minimum tillage was higher than those grown under conventional soil tillage with a disc plough and a mouldboard plough. Plant height was greater in the no-tillage system. The yield of soyabean grown after wheat in system II was higher than in soyabean grown after white oats and wheat in system III and after wheat in system I. The lowest soyabean yield, grain weight per plant and weight of 1000 kernels were obtained in monoculture (wheat/soyabean).
  • Authors:
    • Sweeney, D.
    • Kilgore, G.
    • Whitney, D.
    • Schwab, G.
  • Source: Agronomy Journal
  • Volume: 98
  • Issue: 3
  • Year: 2006
  • Summary: Reduced- and no-tillage seedbed preparation methods coupled with broadcast P applications lead to an accumulation of available P in the surface 0- to 5-cm soil layer and a depletion of available P deeper in the profile. A 3-yr study determined the effects of tillage and fertilizer P management on P uptake and grain yield for P-stratified soils. Tillage practices were moldboard plow (once at the start of the study followed by reduced tillage), reduced tillage (disk followed by field cultivation), and no-tillage. Four P management methods were imposed: (i) no P; (ii) 20 kg P ha -1 applied as a surface broadcast; (iii) 20 kg ha -1 applied as a banded starter, 5 cm to the side and 5 cm below the seed; or (iv) 20 kg ha -1 applied in a deep placed band, 13 to 15 cm on 0.7-m centers. The one-time moldboard plowing produced higher early season dry matter yields for corn ( Zea mays L.), wheat ( Triticum aestivum L.), and soybean [ Glycine max (L.) Merr.] compared with the no-tillage system, but tillage effects on final grain yield were inconsistent. Subsurface placement of P generally increased P uptake and grain yield of corn and sorghum [ Sorghum bicolor (L.) Moench], but had little effect on grain yield of soybean. Results indicate that subsurface applications of P fertilizers should be considered if soil test P is highly stratified within the surface 0- to 15-cm layer and the 15-cm composite is medium or below for available P.
  • Authors:
    • Ferguson, N.
    • Storrie, A.
    • Cook, T.
  • Source: Weed control in summer crops 2005-06
  • Year: 2006
  • Summary: This publication provides a guide to weed control in grain and forage sorghum, maize, sweetcorn, soyabean, sunflower, azuki bean [ Vigna angularis], cowpea, lablab, mung bean, pigeon pea, navy bean [ Phaseolus vulgaris], groundnut and millet in New South Wales, Australia. Information is presented on poison warnings, safety directions and first aid instructions on herbicide labels; successful use of herbicides; managing legal responsibilities in applying herbicides; testing for herbicide residues; tips for tankmixing herbicides; use of adjuvants, surfactants and oils with herbicides; water quality for herbicide application; reduction of herbicide spray loss (drift); nozzle selection for ground application; boomspray preparation and calibration; and cleaning and decontamination of boomsprays. Tabulated data are also given on the compatibility of herbicides with rotation and tillage practices to effectively control weeds affecting summer crops.
  • Authors:
    • Andrioli, I.
    • Pereira, M.
    • Fabian, A.
    • Torres, J.
  • Source: Revista Brasileira de Agrociencia
  • Volume: 12
  • Issue: 1
  • Year: 2006
  • Summary: To evaluate the influence of vegetation coverings on soil temperature and humidity, in a medium texture red distrophic latossol, a study was conducted at CEFET-Uberaba, Minas Gerais, Brazil from January to June 2000. A ramdomized complete split plot block design, with 3 replications was used. Eight vegetation covers were allocated to plots: pearl millet ( Pennisetum americanum [ P. glaucum] sin. tiphoides), braquiaria ( Brachiaria brizantha [ Urochloa brizantha]), sorghum ( Sorghum bicolor), pigeon pea ( Cajanus cajan), sun hemp ( Crotalaria juncea) and black oat ( Avena strigosa [ A. nuda]), fallow land and area under conventional system (control). In subplots, maize and soyabean were planted, after vegetation cover desiccation. No significant differences were found among vegetation coverings in relation to soil hydric regime but differences among months were observed. Effect of vegetation cover on soil temperature was shown effectively during the months of May and June, in terms of residues of cultivated crops, mainly maize. Higher values in thermal amplitude were detected under soyabean cropping. Temperatures were higher at 5 cm depth than at 10 cm, in afternoons, under maize and soyabean cultivation.
  • Authors:
    • Li, H. W.
    • Li, B.
  • Source: Transactions of the Chinese Society for Agricultural Machinery
  • Volume: 37
  • Issue: 3
  • Year: 2006
  • Summary: A no-till planter for wheat that can work on the field bestrewing whole maize straw was developed. Because a specific row planter was used in the machine, it is only required to chop the straw and not to chop the root. Compared with a rotary cultivator for chopping and covering stubbles in soil, the performance of the planter was better, and its anti-blocking effect was outstanding.