• Authors:
    • Travis, G. R.
    • Larney, F. J.
    • Chang, C.
    • Hao, X.
  • Source: Journal of Environmental Quality
  • Volume: 30
  • Issue: 2
  • Year: 2001
  • Summary: The emission of greenhouse gases (GHG) during feedlot manure composting reduces the agronomic value of the final compost and increases the greenhouse effect A study was conducted to determine whether GHG emissions are affected by composting method. Feedlot cattle manure was composted with two aeration methods-passive (no turning) and active (turned six times). Carbon lost in the forms of CO2 and CH4 was 73.8 and 6.3 kg C Mg-1 manure for the passive aeration treatment and 168.0 and 8.1 kg C Mg-1 manure for the active treatment. The N loss in the form of N2O was 0.11 and 0.19 kg N Mg-1 manure for the passive and active treatments. Fuel consumption to turn and maintain the windrow added a further 4.4 kg C Mg-1 manure for the active aeration treatment. Since CH4 and N2O are 21 and 310 times more harmful than CO2 in their global warming effect, the total GHG emission expressed as CO2-C equivalent was 240.2 and 401.4 kg C Mg-1 manure for passive and active aeration. The lower emission associated with the passive treatment was mainly due to the incomplete decomposition of manure and a lower gas diffusion rate. In addition, turning affected N transformation and transport in the windrow profile, which contributed to higher N2O emissions for the active aeration treatment. Gas diffusion is an important factor controlling GHG emissions. Higher GHG concentrations in compost windrows do not necessarily mean higher production or emission rates.
  • Authors:
    • Dabney,S. M.
    • Delgado,J. A.
    • Reeves,D. W.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 32
  • Issue: 7-8
  • Year: 2001
  • Summary: This article reviews literature about the impacts of cover crops in cropping systems that affect soil and water quality and presents limited new information to help fill knowledge gaps. Cover crops grow during periods when the soil might otherwise be fallow. While actively growing, cover crops increase solar energy harvest and carbon flux into the soil, providing food for soil macro and microrganisms, while simultaneously increasing evapotranspiration from the soil. Cover crops reduce sediment production from cropland by intercepting the kinetic energy of rainfall and by reducing the amount and velocity of runoff. Cover crops increase soil quality by improving biological, chemical and physical properties including: organic carbon content, cation exchange capacity, aggregate stability, and water infiltrability. Legume cover crops contribute nitrogen (N) to subsequent crops. Other cover crops, especially grasses and brassicas, are better at scavenging residual N before it can leach. Because growth of these scavenging cover crops is usually N limited, growing grass/legume mixtures often increases total carbon inputs without sacrificing N scavenging efficiency. Cover crops are best adapted to warm areas with abundant precipitation. Water use by cover crops can adversely impact yields of subsequent dryland crops in semiarid areas. Similarly, cooler soil temperatures under cover crop residues can retard early growth of subsequent crops grown near the cold end of their range of adaptation. Development of systems that reduce the costs of cover crop establishment and overcome subsequent crop establishment problems will increase cover crop utilization and improve soil and water quality.
  • Authors:
    • Ries, R.
    • Merrill, S.
    • Krupinsky, J.
    • Tanaka, D.
  • Source: Proceedings of the 5th International Safflower Conference, Williston, North Dakota and Sidney, Montana, USA, 23-27 July, 2001. Safflower: a multipurpose species with unexploited potential and world adaptability
  • Year: 2001
  • Summary: Safflower is a good crop to include in cereal based cropping systems in the Northern Great Plains of the USA and Canada because it is adapted to semi-arid regions of the world. No-till field research was conducted 11 km southwest of Mandan, ND to determine the influences of previous crop and crop residue on safflower ( Carthamus tintorius) production. Four replicates of safflower were seeded over ten crop residues [canola ( Brassica napus), crambe ( Crambe abysinnica), dry pea ( Pisum sativum L.), dry bean ( Phaseolus vulgaris L.), flax ( Linum usitatissimum L.), safflower, soybean (Glycine max (L.) Merr.), sunflower ( Helianthus annuus L.), wheat ( Triticum aestivum L.), and barley ( Hordeum vulgare L.)] in 1999 and 2000. Averaged over the two years, surface residue cover after seeding safflower was the highest for wheat, barley, and flax (95 to 86%) and the lowest for dry pea, dry bean, and sunflower (82 to 31%). Safflower production after flax, barley, wheat, and dry pea was 220 to 150% greater than safflower production after safflower. The sustainability of diversified cropping systems that include safflower will be determined by the previous crop and crop residues and the crop sequence in which safflower is grown.
  • Authors:
    • Powell, C.
  • Source: New South Wales Department of Agriculture
  • Year: 2001
  • Summary: Variety trials conducted in New South Wales, Australia in 2000 are reported for winter crops of barley, canola [rape], chickpeas, faba beans, field peas, lentils, lupins ( Lupinus albus and L. angustifolius), mixed cereals, oats, triticale and wheat.
  • Authors:
    • Choudhary, A.
    • Akramkhanov, A.
    • Pulatov, A.
  • Source: Conservation agriculture, a worldwide challenge. First World Congress on conservation agriculture, Madrid, Spain, 1-5 October, 2001. Volume 2
  • Year: 2001
  • Summary: This paper describes the status of agriculture and environmental issues in Uzbekistan and other Central Asian states. The paper also outlines the recent research and development project being conducted in Uzbekistan to promote conservation agriculture technologies for wheat and cotton production. No-tillage and bed planting technologies were trialled for the first time in Uzbekistan to grow winter wheat at the Tashkent Institute of Irrigation and Agricultural Mechanisation Engineers Research Farm. These were compared to conventionally grown wheat. Wheat yield obtained was 3.44, 3.96 and 3.57 t/ha in no-till, bed planting and conventional fields respectively. These results suggest a high potential for irrigated wheat crop production with the use of such technologies in Uzbekistan.
  • Authors:
    • Schillinger, W. F.
  • Source: Soil Erosion Research for the 21st Century, Proc. Int. Symp. (3-5 January 2001, Honolulu, HI, USA). Eds. J.C. Ascough II and D.C. Flanagan. St. Joseph, MI: ASAE.701P0007
  • Year: 2001
  • Summary: Water runoff and soil loss from wheat fields in the inland Pacific Northwest (PNW) USA is often severe during the winter when rain or snow melt occur on frozen soils. Annual precipitation in this region varies from 150 to 600 mm and characteristically 60% occurs between November and March. Water erosion in the wheat-fallow rotation is most severe during the winter of the crop year because of the winter precipitation pattern, long steep slopes, very little ground cover from crop residue or wheat seedlings, and low water infiltration rates through frozen soil. Additional management practices are needed to combat erosion events associated with frozen soil. Research was conducted at 9 on-farm sites in eastern Washington state from 1993 to 1999 to determine the effects of subsoiling fall-sown wheat on 15 to 40% slopes prior to soil freezing on soil loss, water infiltration into the soil, and grain yield. The experimental design at each site was a randomized complete block with 6 replications of 2 treatments: subsoiled and control. Two types of subsoilers were used over the 6-yr period: (i) a 5-cm-wide shank operated 40 cm deep on the contour with shanks spaced 4 or 6 m apart to cut a continuous groove in the soil, and (ii) a rotary 'sharks tooth' implement which creates a 40 cm deep, 4-litre-capacity hole every 0.7 m 2. The sharks tooth subsoiler causes less soil disturbance and less damage to wheat plants than continuous shank channels. Results show that, when water runoff on frozen soils occurs, tillage channels or holes (i) reduce soil loss by retarding rill erosion, (ii) increase water infiltration, and (iii) do not reduce or increase grain yield. Many wheat growers have started to adopt these, or similar, soil conservation practices on their farms.
  • Authors:
    • Stout, J. E.
  • Source: Journal of Arid Environments
  • Volume: 47
  • Issue: 4
  • Year: 2001
  • Summary: Continuous measurements of dust reveal the intermittent nature of dust events within the Southern High Plains of North America. Dust events appear as sudden peaks that project outward from a much lower background dust concentration. The measured dust record appears to follow a regular annual cycle with most dust events occurring in spring and considerably fewer during other seasons. The annual dust cycle reflects seasonal changes in environmental factors such as wind speed, surface cover, and moisture conditions. Most dust events are associated with a combination of strong winds, negligible surface cover? and dry conditions, all of which occur most frequently during the spring season. Wind speed alone is found to be an imperfect indicator of dust levels in the Southern High Plains because of the moderating effects of other important environmental factors such as humidity and surface cover. However, if one limits consideration to dry and bare conditions, dust concentration exhibits a positive correlation with daily wind speeds above 4 m s(-1) and a negligible correlation for light winds.
  • Authors:
    • Zybalov, V.
  • Source: Mezhdunarodnyi Sel'skokhozyaistvennyi Zhurnal
  • Issue: 5
  • Year: 2001
  • Summary: Field trials were carried out at 2 sites in Russia to assess the effectiveness of rape as a weed-removing crop in different rotations. Rotations were fallow-wheat-barley-maize-wheat, and vetch-oat mixture and rape-wheat-barley-maize-wheat, with a control involving pure fallow. The degree of weediness (number of weeds/m 2) and species composition of weeds in young crops of wheat and barley was assessed twice (at tillering stage and before harvest). Before harvesting, weed mass was also assessed and the numbers of weed seeds in soil samples were determined. The substitution of rape crops for fallow in rotations resulted in significant reductions in weed numbers and weed seeds in soil. It is concluded that rape is effective in reducing levels of weeds in young crops and soils, even when minimal or no soil preparation is carried out.
  • Authors:
    • Sojka, R. E.
    • Bjorneberg, D. L.
    • Aase, J. K.
  • Source: Transactions of the ASAE
  • Volume: 44
  • Issue: 3
  • Year: 2001
  • Summary: Zone subsoiling on irrigated land has been successfully used to improve potato ( Solanum tuberosum) yield and quality. Zone subsoiling under furrow irrigation may disrupt water flow and influence infiltration and soil erosion. We hypothesized that zone subsoiling, done appropriately, will maintain integrity of irrigation furrows, improve small grain (barley) and dry bean ( Phaseolus vulgaris) growth and yield, and not adversely affect water flow, infiltration, or erosion on furrow-irrigated soils. The experiment, which started in 1995, was conducted at the USDA-ARS Northwest Irrigation and Soils Research Laboratory in Kimberly, Idaho, USA. The soil is a Portneuf silt loam (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids). Tillage treatments were disc, disc+paratill, paratill, and no-till. There were no differences in water infiltration, runoff, or soil erosion among treatments. Bulk density differences among treatments were largest at the 0.15 to 0.20-m depth, and bulk density was ~16 to 18% greater on disc and no-till treatments than on paratill treatments. The highest frequency of low cone index (CI) values belonged to paratill treatments (65 to 80% frequency of CI values less than 2 MPa); the lowest frequency of low CI values belonged to no-till treatment (20% frequency less than 2 MPa). Cone index versus bulk density relationships depended on soil water content with a slope of 5.81 (r 2=0.70) in the wetter year of 1997, and 2.90 in the drier year of 1995 (r 2=0.60). Subsoiling can be accomplished on furrow-irrigated lands with no adverse effects on runoff, infiltration, and erosion, but under our conditions did not improve crop growth and yield.
  • Authors:
    • Ayuk, E. T.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 61
  • Issue: 1-2
  • Year: 2001
  • Summary: In recent years and in some situations the status of soil organic matter (SOM) has deteriorated considerably due to long periods of continuous cultivation and limited external inputs in the form of mineral fertilizers. Deterioration of SOM varies by agro-ecological zones, by soil types and by cropping patterns. It is more intense in East Africa, followed by coastal West Africa and Southern Africa and least intensive in the Sahel and Central Africa. It is also more serious in areas under low-input agriculture irrespective of the prevailing cropping system. The major consequence of the decrease in SOM in the tropics is lower agricultural productivity with a direct negative effect on food security. While biophysical dynamics of SOM have been extensively covered in the literature, social considerations have not received similar attention. This paper examines the social, economic and policy factors associated with the management of tropical soil organic matter. Empirical data from a range of environments in Africa show that SOM improvement options yield a positive return to land as well as labour. However, there are a number of constraints. Social constraints are related to the large quantities of organic matter that are required (case of farmyard manure), the competitive uses for the material (case of crop residues), land and labour requirements, and gender-related issues. From a policy stand point, unsecured tenure rights together with price distortions and other market failures may be important constraints. Challenges for sustainable management of SOM are identified. These include management conflicts, land tenure arrangements, the divergence in goals between individuals and society, land and labour requirements, inadequate support systems for land users, profitability issues, the role of subsidies, and the absence of national action plans. A number of opportunities are identified that could enhance the improvement or maintenance of SOM. These include: exploring the need and potential role of community-based SOM management practices; development of an integrated plant nutrient management strategy involving both organic and inorganic inputs; and development of concrete national action plans. It is argued that because externalities of SOM improvement or maintenance extend beyond the farmer's fields, SOM investment may require cost sharing between individuals and the society. Policies on subsidies need to be reconsidered. Research priorities are identified that require closer collaboration between scientists from a variety of disciplines.