• Authors:
    • Richardson, J.
    • Hons, F.
    • Ribera, L.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 2
  • Year: 2004
  • Summary: Tillage systems that reduce the number of cultivation steps can, according to soil scientists, save soil moisture, fuel, labour, and machinery costs, as well as reduce wind and water erosion. However, many producers in south Texas, USA, are reluctant to adopt these practices. The objective of this study was to compare the economics of conventional tillage (CT) and no-tillage (NT) systems on three commercial crops produced in south Texas: grain sorghum ( Sorghum bicolor), wheat ( Triticum aestivum), and soyabean ( Glycine max). When considering the economics of both tillage systems, three areas affecting profit were addressed: changes in cost per hectare, changes in yield per hectare, and the impact on net income risk. Empirical distributions of net income for different tillage systems under risk were estimated using a Monte Carlo simulation model of net income per hectare. Certainty equivalents were used to rank the tillage systems because they can be used to rank risky alternatives for risk-averse decision makers. The risk premium for risk-averse decision makers who prefer NT over CT ranges between $12.60 and $34.25 per hectare for all five crop rotations. Risk-neutral decision makers would prefer continuous sorghum and sorghum-wheat-soyabean rotation over all other rotations under CT and NT, respectively. However, risk-averse decision makers would prefer continuous sorghum over all other rotations either under CT or NT. The results suggest that under risk-neutral rankings, NT would be preferred over CT in three out of the five crop rotations tested. However, assuming a risk-averse decision maker, NT would be preferred over CT in all five crop rotations.
  • Authors:
    • Carmo, C.
    • Lhamby, J.
    • Ambrosi, I.
    • Santos, H.
  • Source: Ciencia Rural
  • Volume: 34
  • Issue: 1
  • Year: 2004
  • Summary: Soil tillage and crop rotation and succession systems were assessed in Passo Fundo, Rio Grande do Sul, Brazil, from 1994/95 to 1997/98. Four soil tillage systems, i.e. no-tillage, minimum tillage, conventional tillage using a disc plough, and conventional tillage using a mouldboard plough, and three crop rotation and succession systems, i.e. system I (wheat/soyabean), system II (wheat/soyabean and common vetch [ Vicia sativa]/sorghum or maize) and system III (wheat/soyabean, common vetch/sorghum or maize, and white oats/soyabean), were compared. An experimental design of randomized blocks with split-plots and three replications was used. The main plot was formed by the soil tillage systems, while the split-plots consisted of the crop rotation and succession systems. Two types of analysis were applied to the net return of soil tillage and crop rotation and succession systems: mean-variance and risk analysis. By the mean-variance analysis, no-tillage and minimum tillage, which presented higher net returns, were the best alternatives to be offered to the farmer. By the stochastic dominance analysis, no-tillage and crop rotation with two winters without wheat showed the highest profit and the lowest risk.
  • 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, 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:
    • 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.