• Authors:
    • Scott, A. W.,Jr.
    • Westphal, A.
  • Source: Crop Science
  • Volume: 45
  • Issue: 1
  • Year: 2005
  • Summary: Rotylenchulus reniformis Linford & Oliveira is increasing in incidence in cotton-growing areas throughout the southern USA east of New Mexico. Cotton (Gossypium hirsutum L.) cultivars resistant to R. reniformis are currently unavailable. Management depends on a crop sequence with nonhosts of the nematode. In South Texas, the sequence of cotton with grain sorghum [ Sorghum bicolor (L.) Moench] or corn ( Zea mays L.) has become a standard practice. To improve farm efficiency, the implementation of rotation crops that are economically superior to grain sorghum is desirable. Eighteen cultivars of soybean [ Glycine max (L.) Merr.] were tested in nonfumigated and in fumigated sandy loam soil infested with R. reniformis to evaluate nematode resistance of soybean under field conditions. Shank application of 1,3-dichloropropene at a 38-cm depth reduced R. reniformis population densities at the 15- to 60-cm depth compared with preseason counts. The effect of each soybean cultivar on the growth and yield of a subsequent cotton crop was compared with the impact of grain sorghum and fallow. High-yielding cultivars of soybean (HY574, Padre, DP7375RR, and NK83-30) with reniform nematode-suppressing potential were identified among cultivars within maturity groups 5, 6, 7, and 8. In contrast, cotton yields following the susceptible cultivars Santa Rosa-R, Vernal, and DP6880RR were on average 25% lower than those following grain sorghum. The enrichment of cotton sequences with reniform nematode-resistant soybean cultivars is viable when the proper cultivars are chosen, whereas the use of reniform nematode-susceptible soybean cultivars is discouraged. The effective use of R. reniformis-resistant soybean cultivars to manage R. reniformis in cotton will depend on a number of additional economic parameters not studied in these experiments.
  • 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:
    • Shea, K. L.
    • Gregory, M. M.
    • Bakko, E. B.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 20
  • Issue: 2
  • Year: 2005
  • Summary: We compared soil characteristics, runoff water quantity and nutrient fluxes, energy use and productivity of three farm types in an unusually dry farming season: conventional (continuous corn and deep tillage), rotation (5-year corn-soybean-oats/ alfalfa-alfalfa-alfalfa rotation with tillage 2/5 years) and no-till (corn-soybean with no cultivation). Soil organic matter content was highest on the rotation farm, followed by the no-till farm, and lowest on the conventional farm. Nitrate content of the soil did not differ significantly among the three farms, although the conventional farm had a much higher input of fertilizer nitrogen. Soil penetrometer resistance was lower and percent soil moisture was higher in the no-till and rotation systems compared to the conventional farm. Soil macroinvertebrate abundance and diversity were highest on the no-till farm, followed by the rotation farm. No invertebrates were found in the soil of the conventional farm. The conventional farm had the highest runoff volume per cm rain and higher nitrogen (N) loss in runoff when compared to the rotation and no-till farms, as well as a higher phosphorus (P) flux in comparison to the no-till farm. These results indicate that perennial close-seeded crops (such as alfalfa) used in crop rotations, as well as plant residue left on the surface of no-till fields, can enhance soil organic content and decrease runoff. The lower soil penetrometer resistance and higher soil moisture on the rotation and no-till farms show that conservation tillage can increase soil aggregation and water infiltration, both of which prevent erosion. Furthermore, crop rotation, and particularly no-till, promote diverse invertebrate populations, which play an important role in maintaining nutrient cycling and soil structure. Crop rotation and no-till agriculture are less fossil-fuel intensive than conventional agriculture, due to decreased use of fertilizers, pesticides and fuel. In this unusually dry year they provided superior corn and soybean yields, most likely due to higher soil moisture as a result of greater water infiltration and retention associated with cover crops (rotation farm) and crop residue (no-till farm).
  • Authors:
    • Guerke, W. R.
  • Source: Seed Technology
  • Volume: 27
  • Issue: 1
  • Year: 2005
  • Summary: These proceedings, containing 5 sections, include a report on an innovative seed vigour imaging system for soyabean and maize seedlings developed at the Ohio State University. Manuscripts on topics such as DNA extraction from soyabeans, enhancement of germination in tomato, antioxidant capacity in tomato genotypes, harvest maturity and drying of okra seed, breeding strategy for a Chinese cotton cultivar, fruit and seed development in cowpea and identification of seeds from landscape soils are presented. Reports on Phomopsis detection and pathogenicity in soyabean, a chromosomes squash technique to determine mitotic activity, utility of phenotypic traits in coconut palm for seed production and accelerated aging of oil palm seeds are also presented. Papers on the current state of vigour testing for cotton, groundnuts, rice, sorghum and soyabeans, as well as on hybrid purity testing of maize and germination and stand establishment of polymer coated rape seeds subjected to various stress conditions are included.
  • Authors:
    • Peterson, G. A.
    • Westfall, D. G.
  • Source: Annals of Applied Biology
  • Volume: 144
  • Issue: 2
  • Year: 2004
  • Summary: In the Great Plains of North America potential evaporation exceeds precipitation during most months of the year. About 75% of the annual precipitation is received from April through September, and is accompanied by high temperatures and low relative humidity. Dryland agriculture in the Great Plains has depended on wheat production in a wheat-fallow agroecosystern (one crop year followed by a fallow year). Historically this system has used mechanical weed control practices during the fallow period, which leaves essentially no crop residue cover for protection against soil erosion and greatly accelerates soil organic carbon oxidation. This paper reviews the progress made in precipitation management in the North American Great Plains and synthesises data from an existing long-term experiment to demonstrate the management principles involved. The long-term experiment was established in 1985 to identify dryland crop and soil management systems that would maximize precipitation use efficiency (maximization of biomass production per unit of precipitation received), improve soil productivity, and increase economic return to the farmers in the West Central portion of the Great Plains. Embedded within the primary objective are subobjectives that focus on reducing the amount of summer fallow time and reversing the soil degradation that has occurred in the wheat-fallow cropping system. The experiment consists of four variables: 1) Climate regime; 2) Soils; 3) Management systems; and 4) Time. The climate variable is based on three levels of potential evapotranspiration (ET), which are represented by three sites in eastern Colorado. All sites have annual long-term precipitation averages of approximately 400-450 mm, but vary in growing season open pan evaporation from 1600 mm in the north to 1975 mm in the south. The soil variable is represented by a catenary sequence of soils at each site. Management systems, the third variable, differ in the amount of summer fallow time and emphasize increased crop diversity. All systems are managed with no-till techniques. The fourth variable is time, and the results presented in this paper are for the first 12 yr (3 cycles of the 4-yr system). Comparing yields of cropping systems that differ in cycle length and systems that contain fallow periods, when no crop is produced, is done with a technique called "annualisation". Yields are "annualised" by summing yields for all crops in the system and dividing by the total number of years in the system cycle. For example in a wheat-fallow system the wheat yield is divided by two because it takes 2 yr to produce one crop. Cropping system intensification increased annualised grain and crop residue yields by 75 to 100% compared to wheat-fallow. Net return to farmers increased by 25% to 45% compared to wheat-fallow. Intensified cropping systems increased soil organic C content by 875 and 1400 kg ha(-1), respectively, after 12 yr compared to the wheat-fallow system. All cropping system effects were independent of climate and soil gradients, meaning that the potential for C sequestration exists in all combinations of climates and soils. Soil C gains were directly correlated to the amount of crop residue C returned to the soil. Improved macroaggregation was also associated with increases in the C content of the aggregates. Soil bulk density was reduced by 0.01g cm(-1) for each 1000 kg ha(-1) of residue addition over the 12-yr period, and each 1000 kg ha(-1) of residue addition increased effective porosity by 0.3%. No-till practices have made it possible to increase cropping intensification beyond the traditional wheat-fallow system and in turn water-use efficiency has increased by 30% in West Central Great Plains agroecosystems. Cropping intensification has also provided positive feedbacks to soil productivity via the increased amounts of crop residue being returned to the soil.
  • Authors:
    • Williams, S.
    • Weil, R.
  • Source: Soil Science Society of America Journal
  • Volume: 68
  • Issue: 4
  • Year: 2004
  • Summary: Deep-rooted cover crops may help alleviate effects of soil compaction, especially in no-till systems. We evaluated the compaction-alleviating ability of 4 cover crops (rape, oilseed radish, forage radish and cereal rye). The experiments were conducted at the University of Maryland Wye Research Station and Education Centre on a Mattapex silt loam (Aquic Hapludults) and at the USDA Beltsville Agricultural Research Centre on an Elkton silt loam (Typic Endoaquults). Using a minirhizotron camera, we observed soyabean ( Glycine max) roots growing through compacted plough pan soil using channels made by decomposing cover crop roots. Soyabean yield response to the preceding cover crops was most pronounced at the site with most severe drought and soil compaction. At this location, with or without deep tillage, soyabean yields were significantly greater following a forage radish cv. Diachon+rye combination cover crop. Rye left a thick mulch, resulting in conservation of soil water early in the season. Root channels left by forage radish may have provided soyabean roots with low resistance paths to subsoil water. Due to lower than normal winter precipitation, this study was a conservative test of the cover crops' ability to alleviate the effects of soil compaction.
  • Authors:
    • Nissen, T.
    • Wander, M.
  • Source: Mitigation and Adaptation Strategies for Global Change
  • Volume: 9
  • Issue: 4
  • Year: 2004
  • Summary: Immediate efforts to increase soil carbon sequestration and minimize terrestrial greenhouse gas emissions are needed to mitigate global warming. Whether or not terrestrial stocks become sinks or net sources of C over the next century will depend upon how fast and at what level we are able to stabilize carbon dioxide levels. The cost of soil C sequestration is at present relatively low compared to other C emission reduction technologies making soil C sinks an important short-term solution to be used while competing technologies are developed. However,efforts to use C sequestration in soils as CO2 emissions offsets have faced numerous challenges. Difficulties associated with C stock validation (direct measurement) and the impermanence and saturability of soil C reservoirs raise concerns over whether soil C reservoirs are good long-term investments. Pragmatism has led to the development of indirect inventorying of the C reserves held at national and regional scales. Such indirect accounting systems will advance as validation methods are refined and as process models improve their ability to accurately predict how existing soil condition and specific land management practices will influence soil C storage and NO2 and CH4 emissions. Improved documentation of the value of environmental services and sustained productive potential derived from optimized land use and associated increases in soil quality will also add to the estimated value of soil C sinks. Policies must evolve simultaneously with the theoretical and technical tools needed to promote optimization of land use practices to mitigate climate change now and to minimize future contributions of soil C to atmospheric CO2.
  • Authors:
    • Linden, D. R.
    • Voorhees, W. B.
    • Hatfield, J. L.
    • Johnson, J. M. F.
    • Wilhelm, W. W.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 1
  • Year: 2004
  • Summary: Society is facing three related issues: overreliance on imported fuel, increasing levels of greenhouse gases in the atmosphere, and producing sufficient food for a growing world population. The U.S. Department of Energy and private enterprise are developing technology necessary to use high-cellulose feedstock, such as crop residues, for ethanol production. Corn (Zea mays L.) residue can provide about 1.7 times more C than barley (Hordeum vulgare L.), oat (Avena sativa L.), sorghum [Sorghum bicolor (L.) Moench], soybean [Glycine max (L.) Merr.], sunflower (Helianthus annuus L.), and wheat (Triticum aestivum L.) residues based on production levels. Removal of crop residue from the field must be balanced against impacting the environment (soil erosion), maintaining soil organic matter levels, and preserving or enhancing productivity. Our objective is to summarize published works for potential impacts of wide-scale, corn stover collection on corn production capacity in Corn Belt soils. We address the issue of crop yield (sustainability) and related soil processes directly. However, scarcity of data requires us to deal with the issue of greenhouse gases indirectly and by inference. All ramifications of new management practices and crop uses must be explored and evaluated fully before an industry is established. Our conclusion is that within limits, corn stover can be harvested for ethanol production to provide a renewable, domestic source of energy that reduces greenhouse gases. Recommendation for removal rates will vary based on regional yield, climatic conditions, and cultural practices. Agronomists are challenged to develop a procedure (tool) for recommending maximum permissible removal rates that ensure sustained soil productivity.
  • Authors:
    • Wolt, J. D.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 69
  • Issue: 1
  • Year: 2004
  • Summary: The effectiveness of nitrification inhibitors for abatement of N loss from the agroecosystem is difficult to measure at typical agronomic scales, since performance varies at the research field scale due to complex interactions among crop management, soil properties, length of the trial, and environmental factors. The environmental impact of the nitrification inhibitor nitrapyrin on N losses from agronomic ecosystems was considered with emphasis on the Midwestern USA. A meta-evaluation approach considered the integrated responses to nitrification inhibition found across research trials conducted in diverse environments over many years as measured in side- by-side comparisons of fertilizer N or manure applied with and without nitrapyrin. The resulting distributions of response indices were evaluated with respect to the magnitude and variance of the agronomic and environmental effects that may be achieved when nitrification inhibitors are used regionally over time. The indices considered (1) crop yield, (2) annual or season-long maintenance of inorganic N within the crop root zone, (3) NO3-N leached past the crop root zone, and (4) greenhouse gas emission from soil. Results showed that on average, the crop yield increased (relative to N fertilization without nitrapyrin) 7% and soil N retention increased by 28%, while N leaching decreased by 16% and greenhouse gas emissions decreased by 51%. In more than 75% of individual comparisons, use of a nitrification inhibitor increased soil N retention and crop yield, and decreased N leaching and volatilization. The potential of nitrification inhibitors for reducing N loss needs to be considered at the scale of a sensitive region, such as a watershed, over a prolonged period of use as well as within the context of overall goals for abatement of N losses from the agroecosystem to the environment.
  • Authors:
    • Anderson, R. L.
  • Source: Weed Technology
  • Volume: 18
  • Issue: 1
  • Year: 2004
  • Summary: Dryland rotations are changing in the semiarid Great Plains because of no-till systems. Producers now rotate summer annual crops such as corn with winter wheat and fallow, which can disrupt weed population growth because of diverse life cycles among crops. This study estimated changes in weed populations as affected by rotation design, with the goal of suggesting crop sequences that lower weed community density. We used an empirical life-cycle simulation based on demographics of jointed goatgrass and green foxtail to compare various rotations consisting of winter wheat, corn, proso millet, and fallow across a 12-yr period. The simulation indicated that designing rotations to include a 2-yr interval when seed production of either jointed goatgrass or green foxtail is prevented will drastically reduce weed populations. Arranging four different crops in sequences of two cool-season crops, followed by two warm-season crops was the most beneficial for weed management. Fallow, if used, serves in either life-cycle category. However, if the same crop is grown 2 yr in a row, such as winter wheat, the benefit of rotation design on weed density is reduced considerably. Impact of rotation design on weed density was enhanced by improving crop competitiveness with cultural practices. Rotations with balanced life-cycle intervals not only reduce weed density but enable producers to use alternative weed management strategies, improve effectiveness of herbicides used, and minimize herbicide resistance.