• Authors:
    • O'Connell, P. J.
    • Allard, J. L.
  • Source: Weed management: balancing people, planet, profit. 14th Australian Weeds Conference, Wagga Wagga, New South Wales, Australia, 6-9 September 2004: papers and proceedings 2004
  • Year: 2004
  • Summary: Australian winter broadacre crops have been planted on 19.4 million ha on average, over the five years 1999-2003. The cropped area is dominated by cereals and in particular wheat. Annual ryegrass (ARG, Lolium rigidum) is the most widespread, difficult to control and important weed of Australian winter broadacre farming systems, and is arguably the greatest threat to sustainability of these systems. It was calculated that it infests ~6 million ha. Syngenta's analyses of herbicide sales suggest that the area treated for annual ryegrass could be as high as 8 million ha. Herbicide sales have been used to estimate the area treated for ARG control. This analysis focuses on herbicides for which there is not yet widespread ARG resistance. Grain producers are heavily dependant on two groups of herbicides. Group M (glyphosate) is applied as a non-selective burn-down treatment prior to planting and is applied to as much as 25 million ha (applied up to 132% of the winter crop area). The Group D herbicides, especially trifluralin, are used for pre-emergent weed control on nearly 7 million ha, 36% of the cropped area, up from 25% in 2001. There is circumstantial evidence that Group D herbicides are mostly applied for the management of ARG, and there is a high risk of over-use. Minimum- and no-tillage are used on 76% of the cropped area, while burning as a weed control technique (hot burn) is used on just over 10% of the area. In view of the current willingness of grain growers to rely heavily upon herbicides for weed control, a greater burden is placed on ensuring herbicide rotational strategies are carefully thought through and implemented. This has resulted in extension of double-knockdown techniques with Spray.Seed to reduce the likelihood of glyphosate resistant ARG in reduced tillage environments. A similar education programme needs to be directed towards Group D herbicides and alternatives promoted. Group K herbicides, including S-metolachlor (Dual Gold), are potential alternatives. Group K herbicides are generally well-tolerated by barley, oats, legumes and canola and can be used at higher rates in these crops. Wheat is less tolerant at the rates required to manage ARG effectively. Rotating to Group K herbicides outside wheat is proposed. The grains industry could evaluate the model the Australian cotton industry has established for the very successful management of insecticide resistance. A better way to manage herbicide use and rotation needs to be found, particularly as fewer new active ingredients are expected to be developed than in the past.
  • 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:
    • Porter, G. A.
    • Griffin, T. S.
  • Source: Biology and Fertility of Soils
  • Volume: 39
  • Issue: 5
  • Year: 2004
  • Summary: Information is needed on the ability of different crop management factors to maintain or increase soil C and N pools, especially in intensively tilled short crop rotations. Soil samples from field experiments in Maine were used to assess the effect of cover crop, green manure (GM) crop, and intermittent or annual amendment on soil C and N pools. These field experiments, of 6-13 years' duration, were all characterized by a 2-year rotation with either sweet corn (Zea mays L.) or potato (Solanum tuberosum L.), and primary tillage each year. Total, particulate organic matter (POM), and soil microbial biomass (SMB)-C and -N pools were assessed for each experiment. Total C and N stocks were not affected by red clover (Trifolium pratense L.) cover crop or legume GM, but were increased by 25-53% via a single application of papermill sludge or an annual manure and/or compost amendment. With the exception of continuous potato production which dramatically reduced the SMB-C and SMB-N concentration, SMB-C and -N were minimally affected by changes in cropping sequence, but were quite sensitive to amendments, even those that were primarily C. POM-C and -N, associated with the coarse mineral fraction (53-2,000 mum), were more responsive to management factors compared to total C and N in soil. The change in soil C fractions was a linear function of increasing C supply, across all experiments and treatments. Within these intensively tilled, 2-year crop rotations, substantial C and N inputs from amendments are needed to significantly alter soil C and N pools, although cropping sequence changes can influence more labile pools responsible for nutrient cycling.
  • Authors:
    • Turvey, C. G.
    • Kay, B. D.
    • Joseph, S.
    • Weersink, A.
  • Source: CAFRI: Current Agriculture, Food and Resource Issues
  • Volume: 4
  • Year: 2003
  • Summary: The objective of the 1997 Kyoto agreement was to limit greenhouse gas (GHG) emissions among signatory countries and thereby slow global warming. Under the agreement, Canada has committed itself to reduce GHGs over the next decade by 6 percent from estimated 1990 levels. Debate has now begun on the appropriate government policies that will induce the desired GHG reductions. Regulations could be in the form of direct controls or economic incentives, such as a subsidy/tax system or an emission trading system. The success of the U.S. emission market for SO2 (Schmalenseeet al., 1998) has generated growing interest in the use of a similar market mechanism for carbon (Holmes and Friedman, 2000). The existence of a carbon credit market presents the agricultural sector with another potential revenue source (Sandor and Skees, 1999). While agriculture contributes approximately 10 percent of Canada’s greenhouse gas emissions, it also has the potential to sequester carbon through strategies such as zero tillage, reduced summer fallow and improved grazing. These sequestration activities could be incorporated into an emission trading system and create a “carbon credit” for each unit of CO2 that is removed from the atmosphere. Firms with high emission reduction costs could then buy these credits rather than bear the large abatement costs associated with reducing their GHG emission levels. The perception is that the marginal cost of abatement for agriculture is less than that for other sectors (McCarl and Schneider, 2000). Thus, farmers may be able to profit by selling credits for activities that sequester carbon. An example of such a transaction was the purchase of carbon credits from Iowa farmers who adopted no-till by a consortium of Canadian energy companies (GEMCO) (Lessiter, 1999). Whether the development of a carbon credit market will affect the management decisions of an Ontario crop farmer is the focus of this study.
  • 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:
    • Snyder, G.
    • Wolf, B.
  • Year: 2003
  • Authors:
    • Chan, K. Y.
    • Heenan, D. P.
    • So, H. B.
  • Source: Australian Journal of Experimental Agriculture
  • Volume: 43
  • Issue: 4
  • Year: 2003
  • Authors:
    • Iraj Eskandari
    • Abbas Hemmat
  • Source: Aktualni zadaci mehanizacije poljoprivrede. Zbornik radova, 31. međunarodnog simpozija iz područja mehanizacije poljoprivrede, Opatija, Hrvatska, 24-28 veljač 2003
  • Year: 2003