• Authors:
    • Perfect, E.
    • Herbeck, J.
    • Murdock, L.
    • Grove, J. H.
    • Dí­az-Zorita, M.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 6
  • Year: 2004
  • Summary: The development of well-structured soils is a goal for achieving sustainable and productive agricultural systems. Nevertheless, the maintenance of soil structure in continuous no-till (NT) soils has sometimes been thought to induce soil conditions that are detrimental to crop yields. The objectives of this research were to characterize the effects of periodic tillage disruption in otherwise NT systems on soil properties and the yields of winter wheat (Triticum aestivum L.), double-cropped soybean [Glycine max (L.) Merr.], and maize (Zea mays L.) in rotation and to determine if soil structural changes occurring in tilled soils are independent of changes in other soil properties. A field experiment was established in 1992 on a Huntington silt loam soil (Fluventic Hapludoll) at the University of Kentucky Research and Education Center in Princeton (KY) under a NT crop sequence with two seedbed preparation methods for winter wheat, (a) NT or (b) chisel plus disk tillage (Till). In fall 2000, similar soil chemical properties were observed between disrupted and continuous NT systems over the 0- to 20-cm layer. The geometric mean diameter of dry fragments and the soil water content retained between 0.0003 and 0.03 MPa water potential was greater in NT soils than in soils tilled for winter wheat. Tillage for winter wheat enhanced winter wheat yields (4.2% increase), mostly under low-yielding conditions, but it resulted in a reduction of subsequent summer crop yields (i.e., 3.7% for soybean and 7.0% for maize). The yields obtained in our study translate to an economic benefit for the continuous NT system. Net returns per hectare were estimated to be $73 higher for the winter wheat/double-crop soybean-maize rotation under NT than under Till treatments. The differences in maize yields between NT and tilled treatments were attributed to a better water supply in NT soil due to the maintenance of a larger number of mesopores and a great hydraulic conductivity. In the absence of significant changes in other physicochemical properties, periodic tillage appears to disrupt soil structure, which negatively affects crop productivity.
  • Authors:
    • Scott, A.
    • Ball, B. C.
    • McTaggart, I. P.
    • Akiyama, H.
  • Source: Water, Air, & Soil Pollution
  • Volume: 156
  • Issue: 1-4
  • Year: 2004
  • Summary: Agricultural soil is a major source of nitrous oxide (N2O), nitric oxide (NO) and ammonia (NH3). Little information is available on emissions of these gases from soils amended with organic fertilizers at different soil water contents. N2O, NO and NH3 emissions were measured in large-scale incubations of a fresh sandy loam soil and amended with four organic fertilizers, [poultry litter (PL), composted plant residues (CP), sewage sludge pellets (SP) and cattle farm yard manure (CM)], urea fertilizer (UA) or a zero-N control (ZR) for 38 days. Fertilizers were added to soil at 40, 60 or 80% water-filled pore space (WFPS). The results showed that urea and organic fertilizer were important sources of N2O and NO. Total N2O and NO emissions from UA ranged from 0.04 to 0.62%, and 0.23 to 1.55% of applied N, respectively. Total N2O and NO emissions from organic fertilizer treatments ranged from 0.01 to 1.65%, and <0.01 to 0.55% of applied N, respectively. The lower N2O and NO emissions from CP and CM suggested that applying N is these forms could be a useful mitigation option. Comparison of the NO-N/N2O-N ratio suggested that nitrification was more dominant in UA whereas denitrification was more dominant in the organic fertilizer treatments. Most N was lost from PL and UA as NH3, and this was not influenced significantly by WFPS. Emissions of NH3 from UA and PL ranged from 62.4 to 69.6%, and 3.17 to 6.11% of applied N, respectively.
  • 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:
    • 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:
    • Rich, J.
    • Wiatrak, P.
    • Katsvairo, T.
    • Marois, J.
    • Wright, D.
  • Source: Proceedings of the 26th Southern Conservation Tillage Conference for Sustainable Agriculture, Raleigh, North Carolina, USA, 8-9 June, 2004
  • Year: 2004
  • Summary: Soils in the southeast have low organic matter content, low native fertility, and low water holding capacity which has resulted in stagnant yields. Long term studies across the country (Morrow, Sanborn, Magruder, Old Rotation [Auburn]) have shown that land coming out of long term perennial grasses often has an organic matter content of over 4% and decreases as it stays in continuous annual cropping and levels off after 80-100 years once the level reaches about 1 1/2% with use of conservation tillage, cover crops, proper rotation, and modern fertility practices. Years of research in the southeast have shown that perennial grasses such as bahiagrass can help improve soil structure and reduce pests such as nematodes and increase crop yields, sometimes dramatically. Research in the southeast with this perennial grasses grown in rotation with crops has shown higher yields (50% more groundnuts than under conventional annual cropping systems), increased infiltration rates (more than 5 times faster), higher earthworm numbers (thousands per acre vs. none in many cases), and a more economically viable (potential for 3-5 times more profit) cropping system. Diversification into livestock can add another dimension to the farming system making it more intensive and provide a readily available use for perennial grasses.
  • Authors:
    • Sanders, D. C.
    • Paullier, J.
    • Maeso, D.
    • Arboleda, J.
    • Gilsanz, J. C.
    • Hoyt, G. D.
    • Behayout, E.
    • Lavandera, C.
  • Source: Proc. XXVI IHC – Sustainability of Horticultural Systems Eds. L. Bertschinger and J.D. Anderson Acta Horticulturae 638, ISHS 2004
  • Issue: 638
  • Year: 2004
  • Summary: Seven rotational systems were evaluated for vegetable crops in USA and Uruguay. Rotational systems that include both winter and summer cover crops and vegetable crops were used. Treatments comprised: continuous cropping system, T1; multiple vegetable system, T2; green manure system, T3; chicken manure system, T4; fallow system, T5; strip tillage system, T6; and no-tillage system, T7. The crops used were sweet potato, squash, oat or triticale winter cover crop, sorghum or Sudan grass summer cover crop, sweetcorn, garlic, carrot with chicken manure and fallow. Different insects, diseases and weed infestations were recorded in the systems. The study began in spring 1999 in Uruguay and spring 2000 in North Carolina, USA. This paper reports only results from Uruguay. The yields obtained were good compared to the national average in most cases. The average yield is 7 t/ha for sweet potato and 3.5 t/ha for garlic. T6 had the highest soil macrofauna (70 worms/m 2 compared to 4.2 in T1). Soil biomass was sampled for four times: 13 April, 26 May, 17 August and 08 November 2000. T7 system had greater soil biomass during the period of observation than T1 or T4 systems. T6 and T7 treatments had the lowest nitrate levels in the soil among all treatments. T4 was enough for garlic growth. T6, T7 and T4 systems had less sclerotia (from Sclerotium rolfsii [ Corticium rolfsii]) than T1 and T2 systems.
  • Authors:
    • Marland, G.
    • West, T. O.
  • Source: Biogeochemistry
  • Volume: 63
  • Issue: 1
  • Year: 2003
  • Summary: There is a potential to sequester carbon in soil by changing agricultural management practices. These changes in agricultural management can also result in changes in fossil-fuel use, agricultural inputs, and the carbon emissions associated with fossil fuels and other inputs. Management practices that alter crop yields and land productivity can affect the amount of land used for crop production with further significant implications for both emissions and sequestration potential. Data from a 20-year agricultural experiment were used to analyze carbon sequestration, carbon emissions, crop yield, and land-use change and to estimate the impact that carbon sequestration strategies might have on the net flux of carbon to the atmosphere. Results indicate that if changes in management result in decreased crop yields, the net carbon flux can be greater under the new system, assuming that crop demand remains the same and additional lands are brought into production. Conversely, if increasing crop yields lead to land abandonment, the overall carbon savings from changes in management will be greater than when soil carbon sequestration alone is considered.
  • Authors:
    • Chapman, D. F.
    • White, R. E.
    • Chen, D.
    • Eckard, R. J.
  • Source: Australian Journal of Agricultural Research
  • Volume: 54
  • Year: 2003
  • Authors:
    • Harrington, L.
    • Jain, M. C.
    • Robertson, G. P.
    • Grace, P. R.
  • Source: Improving the Productivity and Sustainability of Rice-Wheat Systems: Issues and Impacts
  • Volume: ASA Special Publ
  • Year: 2003
  • Summary: Arable lands in the Indo-Gangetic Plains are already intensively cropped with little scope for expansion because of the competing end uses of land for urbanization and industry. Evidence from long-term experiments in the region indicates that cereal yields are declining, which is in stark contrast to the needed increases in production to meet population demands in the future. The intensification of rice-wheat rotations has resulted in a heavy reliance on irrigation, increased fertilizer usage, and crop residue burning, which all have a direct effect on the variable that most affects global climate change - emissions of greenhouse gases. We estimate that the CO 2 equivalent emissions from a high-input conventionally tilled cropping system with residue burning and organic amendments would equal 8 mg C or 29 mg CO 2 per year if applied to 1 million hectares of the Indo-Gangetic Plains. In a no-till, residue-retained system, with 50% of the recommended NPK application, the total emissions would equal 3.7 mg C or 14 mg CO 2 per year, an effective halving of emissions as we move from a high- to low-input system with improved nutrient use and environmental efficiency. The transition to intensified no-tillage systems, with recommended fertilizer levels, can be both productive and environmentally sound in a world that is rapidly becoming aware of the significant effects of global climate change in both the short and long term.