• Authors:
    • Clayton, G. W.
    • Harker, K. N.
    • Soon, Y. K.
  • Source: Soil Science Society of America Journal
  • Volume: 68
  • Issue: 2
  • Year: 2004
  • Summary: We evaluated weed competition effects on the N economy of field pea (Pisum sativum L.) and the subsequent crop to address the paucity of such information. Plots were seeded to pea, canola (Brassica napus L.) and barley (Hordeum vulgare L.) in 1997 and 1998. Weeds, augmented by cross-seeding experimental plots with oat (Avena sativa L.), were removed with herbicides one and four weeks after crop emergence (WAE). The subsequent barley crop received 0 or 6 g N m(-2). Mean percentage of N derived from the atmosphere (%Ndfa) for the 2 yr, estimated by N-15 isotopic dilution, was 81% for the 4-WAE treatment and 51% for the 1-WAE treatment, indicating that a pea plant subjected to greater weed competition derived more of its N from symbiotic fixation. Total N fixed by pea was not affected by the time of weed removal, however, and total N uptake and seed yield were greater with early weed removal due to less competition for soil N. Early weed removal resulted in net N export in pea seeds (because of higher production) while later weed removal resulted in gains of 1.1 to 1.3 g N m(-2). However, time of weed removal during pea cultivation had no effect on the yield or N uptake of the subsequent barley crop. Higher barley yield and N uptake following pea than following barley were mostly the result of greater N availability. Nitrogen fertilization benefited the subsequent barley regardless of preceding crop type.
  • 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:
    • McRae, F. J.
    • Francis, R. J.
    • Dellow, J. J.
  • Source: Weed control in winter crops 2004
  • Year: 2004
  • Summary: This publication is a guide to chemical weed control in fallows, wheat, barley, oats, cereal rye, triticale, rape, safflower, lentil, linseed, lupin, chickpea, faba bean and field pea in New South Wales, Australia.
  • Authors:
    • Cannon, S. B.
    • Silverstein, K. A. T.
    • Graham, M. A.
    • VandenBosch, K. A.
  • Source: Plant Physiology
  • Volume: 135
  • Issue: 3
  • Year: 2004
  • Summary: We used BLAST [basic logical alignment search tool] algorithms to compare unigene sets from Medicago truncatula, Lotus japonicus [ L. japonicus var. corniculatus] and soyabean ( Glycine max and Glycine soja) to nonlegume ( Hordeum vulgare, Chlamydomonas reinhardtii, Gossypium sp., Vitis vinifera, Mesembryanthemum crystallinum, Lactuca sativa, Pinus sp., Solanum tuberosum, Secale cereale, Sorghum bicolor, Helianthus annuus and Triticum aestivum) unigene sets, to GenBank's nonredundant and expressed sequence tag (EST) databases, and to the genomic sequences of rice ( Oryza sativa) and Arabidopsis thaliana. As a working definition, putatively legume-specific genes had no sequence homology, below a specified threshold, to publicly available sequences of nonlegumes. Using this approach, 2525 legume-specific EST contigs were identified, of which less than 3% had clear homology to previously characterized legume genes. As a first step toward predicting function, related sequences were clustered to build motifs that could be searched against protein databases. Three families of interest were more deeply characterized: F-box related proteins, Pro-rich proteins and cysteine cluster proteins (CCPs). Of particular interest were the >300 CCPs, primarily from nodules or seeds, with predicted similarity to defensins. Motif searching also identified several previously unknown CCP-like open reading frames in A. thaliana. Evolutionary analyses of the genomic sequences of several CCPs in M. truncatula suggest that this family has evolved by local duplications and divergent selection.
  • Authors:
    • Australia, Australian Bureau of Agricultural and Resource Economics
  • Source: Australian Bureau of Agricultural and Resource Economics
  • Issue: 132
  • Year: 2004
  • Summary: An overview of crop production in Australia in 2004 is presented. The crop conditions in New South Wales, Victoria, Queensland, Western Australia and South Australia are described. Cropping areas and yields of winter crops (wheat, barley, oats, rape, lupins, field peas, chickpea, faba beans, lentils, triticale, safflower and vetch) and summer crops (cottonseed, sorghum, rice, maize, sunflowers, soyabeans, groundnuts, mung beans and navy beans) are compared with previous years. Various crop production, precipitation and pricing data are also tabulated.
  • Authors:
    • Australian Bureau of Agricultural and Resource Economics
  • Source: Australian Bureau of Agricultural and Resource Economics
  • Issue: 132
  • Year: 2004
  • Summary: An overview of crop production in Australia in 2004 is presented. The crop conditions in New South Wales, Victoria, Queensland, Western Australia and South Australia are described. Cropping areas and yields of winter crops (wheat, barley, oats, rape, lupins, field peas, chickpea, faba beans, lentils, triticale, safflower and vetch) and summer crops (cottonseed, sorghum, rice, maize, sunflowers, soyabeans, groundnuts, mung beans and navy beans) are compared with previous years. Various crop production, precipitation and pricing data are also tabulated.
  • Authors:
    • Chapman, D. F.
    • White, R. E.
    • Chen, D.
    • Eckard, R. J.
  • Source: Australian Journal of Agricultural Research
  • Volume: 54
  • 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
  • Authors:
    • Yang, H.
    • Walters, D. T.
    • Dobermann, A.
    • Cassman, K. G.
  • Source: Annual Review of Environment and Resources
  • Volume: 28
  • Issue: 1
  • Year: 2003
  • Summary: Agriculture is a resource-intensive enterprise. The manner in which food production systems utilize resources has a large influence on environmental quality. To evaluate prospects for conserving natural resources while meeting increased demand for cereals, we interpret recent trends and future trajectories in crop yields, land and nitrogen fertilizer use, carbon sequestration, and greenhouse gas emissions to identify key issues and challenges. Based on this assessment, we conclude that avoiding expansion of cultivation into natural ecosystems, increased nitrogen use efficiency, and improved soil quality are pivotal components of a sustainable agriculture that meets human needs and protects natural resources. To achieve this outcome will depend on raising the yield potential and closing existing yield gaps of the major cereal crops to avoid yield stagnation in some of the world's most productive systems. Recent trends suggest, however, that increasing crop yield potential is a formidable scientific challenge that has proven to be an elusive goal.