• Authors:
    • Sullivan, D. G.
    • Balkcom, K. S.
    • Lamb, M. C.
    • Rowland, D. L.
    • Faircloth, W. H.
    • Nuti, R. C.
  • Source: Proceedings of the 27th Southern Conservation Tillage Systems Conference, Florence, South Carolina, USA, 27-29 June, 2005
  • Year: 2005
  • Summary: The interaction between reduced irrigation capacity and tillage, including the possible conservation of water with reduced tillage systems, is of vital interest to growers. A field study was initiated in the fall of 2001 to determine crop response under a simulated reduction in irrigation. Three tillage systems were replicated three times each under one of four irrigation levels (100% of a recommended amount, 66%, 33%, and 0% or dryland). Tillage systems were conventional tillage, wide-strip tillage and narrow-strip tillage. The test area was planted in triplicate, in a peanut-cotton-corn rotation, with each crop being present each year. A wheat (cv. AGS 1000) cover crop was drill-seeded each fall on conservation tillage plots. Cover crop termination was performed approximately three weeks prior to planting of each crop species. Tillage was significant for peanut yield and net return at the 0% irrigation level only. No trend in yield was evident, however, net return was consistently high with narrow-strip tillage in all years. Irrigation, at any level greater than 0%, masked tillage effects in both yield and net return. These data confirm the suitability of peanut to conservation tillage practices, including both wide- and narrow-strip tillage.
  • Authors:
    • Kelley, F. S.
    • Shaw, D. R.
    • Flint, S. G.
    • Holloway, J. C.
  • Source: Weed Technology
  • Volume: 19
  • Issue: 2
  • Year: 2005
  • Summary: Field studies were conducted in Mississippi, USA, from 1998 to 2000, to compare weed population shifts in soyabean and cotton using a total glyphosate system, preemergence (PRE) herbicides followed by glyphosate, and a conventional herbicide programme. In the first year of the soyabean study, populations of hemp sesbania ( Sesbania exaltata) were highest for treatments of PRE herbicides followed by either glyphosate or the conventional herbicide programme because of better control from the total glyphosate system. Barnyardgrass ( Echinochloa crus-galli) populations in the first year of the study for the untreated plots were 0 plants/m 2 but increased in the third year to 61 plants/m 2. Flumetsulam + metolachlor followed by glyphosate at the lower rates and the untreated control were the only treatments in which there was an increase in barnyardgrass over the 3-year study. Broadleaf signalgrass ( Urochloa platyphylla) populations increased in the third year with 0.1 kg ai flumetsulam + 2.1 kg ai metolachlor/ha followed by 0.84 kg ae glyphosate/ha, primarily because of reduced competition from lower populations of other weeds such as hemp sesbania. Pitted morningglory ( Ipomoea lacunosa) populations for all treatments decreased in the third year because of good control of this species and the high level of interference from other weed species in the first 2 years. Johnsongrass ( Sorghum halepense) populations decreased in the third year with 0.4 kg ai flumetsulam + 1.1 kg ai metolachlor/ha followed by 0.84 kg glyphosate/ha. Johnsongrass populations decreased with timely glyphosate sequential applications, with 5 plants/m 2 in 1998 and 0 plants/m 2 in 2000. Yields increased from the first year to the second year, corresponding to reduced weed pressure, and yields varied from 710 to 1420 kg/ha. Because of weed pressure, soyabean yields were not different in any of the treatments, including the untreated, although treatments changed the species present. In the cotton study, weed populations over 3 years decreased, with the most significant reductions from the treatments of fluometuron + prometryn + metolachlor followed by either pyrithiobac or glyphosate. Weeds that showed the most significant decline were barnyardgrass and hemp sesbania, whereas johnsongrass increased, with 27 plants/m 2 in treatments of 0.6 kg ai fluometuron + 0.3 kg ai prometryn + 0.7 kg ai metolachlor/ha followed by 0.84 kg glyphosate/ha. Lint cotton yields varied from 0 to 128 kg/ha. Because of the weed pressure, cotton yields were not different in any of the treatments, although treatments changed the species present. This research has shown that weed species can decrease over time with the continued use of any of these herbicide programmes.
  • Authors:
    • NASDA
  • Year: 2004
  • Authors:
    • Cooper, R. J.
    • Carroll, J. P.
    • Cederbaum, S. B.
  • Source: Conservation Biology
  • Volume: 18
  • Issue: 5
  • Year: 2004
  • Summary: Among the major agricultural crops in the southeastern United States, cotton (Gossypium hirsutum L.) generally provides the least suitable habitat for most early successional songbirds. Newer cropping approaches, such as use of conservation tillage and stripcover cropping, offer hope for improving the ecological value of cotton fields. We examined the effects of clover stripcover cropping with conservation tillage versus conventionally grown cotton with either conventional or conservation tillage on avian and arthropod species composition and field use in east-central Georgia. Stripcover fields had higher bird densities and biomass and higher relative abundance of arthropods than both conservation tillage and conventional fields. During migration and breeding periods, total bird densities on stripcover fields were 2-6 times and 7-20 times greater than on conservation and conventional fields, respectively. Abundance and biomass for epigeal arthropods were also greatest on stripcover fields during much of the breeding season. Although the clover treatment attracted the highest avian and arthropod densities, conservation fields still provided more wildlife and agronomic benefits than conventional management. Our findings suggest that both conservation tillage and stripcropping systems will improve conditions for birds in cotton, with stripcropped fields providing superior habitat. The reduction of inputs possible with the clover system could allow farmers to lower costs associated with conventional cotton production by $282-317/ha. This reduction of input, coupled with similar or possibly increased yield over conventional systems makes stripcover cropping not only a good choice for reducing negative impacts on wildlife and surrounding ecosystems, but also an economically desirable one.
  • Authors:
    • Skinner, D. Z.
    • Liang, G. H.
  • Year: 2004
  • Summary: This book contains chapters on: genetic transformation; mechanisms of transgene locus formation; gene stacking through site-specific integration; transgenics of plant hormones and their potential application in horticultural crops; avidin in transgenic maize; genetic engineering protocols and use to enhance stress tolerance in wheat; development and utilization of transformation in Medicago spp.; sorghum transformation for resistance to fungal pathogens and drought; current progress and future prospects in rice transformation; successes and challenges in cotton transformation; progress in transforming the recalcitrant soyabean; progress in vegetable crop transformation and future prospects and challenges; genetic transformation of turfgrass; and risks associated with genetically engineered crops.
  • 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:
    • 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:
    • Bunce, J. A.
  • Source: Oecologia
  • Volume: 140
  • Issue: 1
  • Year: 2004
  • Summary: Reductions in leaf stomatal conductance with rising atmospheric carbon dioxide concentration ([CO 2]) could reduce water use by vegetation and potentially alter climate. Crop plants have among the largest reductions in stomatal conductance at elevated [CO 2]. The relative reduction in stomatal conductance caused by a given increase in [CO 2] is often not constant within a day nor between days, but may vary considerably with light, temperature and humidity. Species also differ in response, with a doubling of [CO 2] reducing mean midday conductances by 50% in others. Elevated [CO 2] increases leaf area index throughout the growing season in some species. Simulations, and measurements in free air carbon dioxide enrichment systems both indicate that the relatively large reductions in stomatal conductance in crops would translate into reductions of
  • Authors:
    • Sharma, R. D.
    • Corrêa, J. C.
  • Source: Pesquisa Agropecuária Brasileira
  • Volume: 39
  • Issue: 1
  • Year: 2004
  • Summary: An experiment was carried out on a heavy red yellow latosol to evaluate crop rotation on herbaceous cotton ( Gossypium hirsutum) yields in no-till system under rainfed Savannah conditions. The treatments were: soyabean-millet ( Pennisetum glaucum)-soyabean-millet-cotton; soyabean-amaranth ( Amaranthus hypochondriacus)-soyabean-forage radish-soyabean-cotton; soyabean-grain sorghum ( Sorghum vulgare [ S. bicolor])-soyabean-grain sorghum-cotton; soyabean-black rye ( Avena strigosa [ A. nuda])-soyabean-black rye-cotton and soyabean-soyabean-cotton. The highest cotton seed yield and best weed control were recorded in the sequence soyabean-millet-soyabean-millet-cotton.
  • Authors:
    • Acosta-Martinez, V.
    • Gill, T. E.
    • Zobeck, T. M.
    • Kennedy, A. C.
  • Source: Biology and Fertility of Soils
  • Volume: 38
  • Issue: 4
  • Year: 2003
  • Summary: Microbes (i.e., fungi and bacteria) are needed to maintain the quality of semiarid soils and crop production. Enzyme (produced by microbes) activities were increased in the soil when cotton was rotated with sorghum or wheat under reduced or no-tillage in comparison to continuous cotton under tillage. Soil bacteria and fungi did not change, according to one analysis conducted, due to crop rotation under reduced or no-tillage in comparison to continuous cotton under tillage. The increases in enzyme activities, however, are indicating that microbes and their enzymes will be increased, and thus nutrients will be more available to plants, more organic matter will be formed, and other soil properties will also positively change if crop rotations with reduced or no-tillage are applied to semiarid soils in comparison to the typical current practice of continuous cotton with tillage.