• Authors:
    • Zhang, M. H.
    • Zhang, L. X.
    • Zhang, J. Q.
    • Watson, C.
  • Source: Acta Agronomica Sinica
  • Volume: 35
  • Issue: 2
  • Year: 2009
  • Summary: A study was conducted in Stoneville, Mississippi, USA, under irrigated conditions to develop predictive models, using a simple and effective model technique which can allow producers to predict soyabean growth and development stages in their fields. The models were constructed using 4-year field data (1998-2001) and validated with the fifth year data (2002). Potential factors affecting stages of soyabean growth and development were considered for developing the models. Affecting factors, such as weeds, insects, diseases and drought stress, were controlled optimally to simplify the modelling procedures. In addition, stepwise regression (SR) analysis, artificial neural networks (ANN), and interpolation approaches were used to construct the models. The modelling of soyabean growth and development processes was separated into 2 distinct periods: vegetative growth stage (V-stage) and reproductive growth stage (R-stage). The models included 10 V-stages (up to V8) and 8 R-stages. In the V-stages models, PD (planting date) and mean relative time-span for planting to a particular stage were the only significant parameters, whereas in R-stage models, PD and MG (maturity group) were significant. The models obtained accurate predictions were only using PD, MG and mean relative time-span from planting to a particular stage. The ANN method provided the greatest accuracy in predicting phenological events, indicating that the ANN method can be effectively applied in crop modelling.
  • Authors:
    • Andresen, D.
    • Das, S.
    • Miller, M.
    • Lauwo, S.
    • Staggenborg, S.
    • Jin, W.
    • Bulatewicz, T.
    • Peterson, J.
    • Steward, D. R.
    • Welch, S. M.
  • Source: Hydrology & Earth System Sciences
  • Volume: 13
  • Issue: 8
  • Year: 2009
  • Summary: Near-term consumption of groundwater for irrigated agriculture in the High Plains Aquifer supports a dynamic bio-socio-economic system, all parts of which will be impacted by a future transition to sustainable usage that matches natural recharge rates. Plants are the foundation of this system and so generic plant models suitable for coupling to representations of other component processes (hydrologic, economic, etc.) are key elements of needed stakeholder decision support systems. This study explores utilization of the Environmental Policy Integrated Climate (EPIC) model to serve in this role. Calibration required many facilities of a fully deployed decision support system: geo-referenced databases of crop (corn, sorghum, alfalfa, and soybean), soil, weather, and water-use data (4931 well-years), interfacing heterogeneous software components, and massively parallel processing (3.8*10 9 model runs). Bootstrap probability distributions for ten model parameters were obtained for each crop by entropy maximization via the genetic algorithm. The relative errors in yield and water estimates based on the parameters are analyzed by crop, the level of aggregation (county- or well-level), and the degree of independence between the data set used for estimation and the data being predicted.
  • Authors:
    • Teasdale, J. R.
    • Hanson, J. C.
    • Hima, B. L.
    • Cavigelli, M. A.
    • Conklin, A. E.
    • Lu, Y. C.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 24
  • Issue: 2
  • Year: 2009
  • Summary: We present the results from enterprise budget analyses for individual crops and for complete rotations with and without organic price premiums for five cropping systems at the US Department of Agriculture-Agricultural Research Service (USDA-ARS) Beltsville Farming Systems Project (FSP) from 2000 to 2005. The FSP is a long-term cropping systems trial established in 1996 to evaluate the sustainability of organic and conventional grain crop production. The five FSP cropping systems include a conventional, three-year no-till corn ( Zea mays L.)-rye ( Secale cereale L.) cover crop/soybean ( Glycine max (L.) Merr)-wheat ( Triticum aestivum L.)/soybean rotation (no-till (NT)), a conventional, three-year chisel-till corn-rye/soybean-wheat/soybean rotation (chisel tillage (CT)), a two-year organic hairy vetch ( Vicia villosa Roth)/corn-rye/soybean rotation (Org2), a three-year organic vetch/corn-rye/soybean-wheat rotation (Org3) and a four- to six-year organic corn-rye/soybean-wheat-red clover ( Trifolium pratense L.)/orchard grass ( Dactylis glomerata L.) or alfalfa ( Medicago sativa L.) rotation (Org4+). Economic returns were calculated for rotations present from 2000 to 2005, which included some slight changes in crop rotation sequences due to weather conditions and management changes; additional analyses were conducted for 2000 to 2002 when all crops described above were present in all organic rotations. Production costs were, in general, greatest for CT, while those for the organic systems were lower than or similar to those for NT for all crops. Present value of net returns for individual crops and for full rotations were greater and risks were lower for NT than for CT. When price premiums for organic crops were included in the analysis, cumulative present value of net returns for organic systems (US$3933 to 5446 ha -1, 2000 to 2005; US$2653 to 2869 ha -1, 2000 to 2002) were always substantially greater than for the conventional systems (US$1309 to 1909 ha -1, 2000 to 2005; US$634 to 869 ha -1, 2000 to 2002). With price premiums, Org2 had greater net returns but also greater variability of returns and economic risk across all years than all other systems, primarily because economic success of this short rotation was highly dependent on the success of soybean, the crop with the highest returns. Soybean yield variability was high due to the impact of weather on the success of weed control in the organic systems. The longer, more diverse Org4+ rotation had the lowest variability of returns among organic systems and lower economic risk than Org2. With no organic price premiums, economic returns for corn and soybean in the organic systems were generally lower than those for the conventional systems due to lower grain yields in the organic systems. An exception to this pattern is that returns for corn in Org4+ were equal to or greater than those in NT in four of six years due to both lower production costs and greater revenue than for Org2 and Org3. With no organic premiums, present value of net returns for the full rotations was greatest for NT in 4 of 6 years and greatest for Org4+ the other 2 years, when returns for hay crops were high. Returns for individual crops and for full rotations were, in general, among the lowest and economic risk was, in general, among the highest for Org2 and Org3. Results indicate that Org4+, the longest and most diverse rotation, had the most stable economic returns among organic systems but that short-term returns could be greatest with Org2.
  • Authors:
    • Hedtcke, J. L.
    • Posner, J. L.
    • Chavas, J. P.
  • Source: Agronomy Journal
  • Volume: 101
  • Issue: 2
  • Year: 2009
  • Summary: This article, the second in a series looking at the Wisconsin Integrated Cropping Systems Trial (WICST), reports on the profitability of six conventional and organic systems, with a focus on net returns and associated risk exposure. Several pricing scenarios were compared to evaluate the impact of government programs and organic price premiums. When net return estimates are made using only neighboring elevator prices (no government programs or organic price premiums), we found that the no-till corn-soybean system [ Zea mays L. and Glycine max (L.) Merr.] was the most profitable grain system, and management intensive rotational grazing (MIRG) the most profitable forage system. When government programs and organic price premiums are included, returns increased by 85 to 110% for the organic grain system corn-soybean-wheat+red clover ( Triticum aestivum L.+ Trifolium pratense L.) and 35 to 40% for the organic forage system [companion seeded alfalfa with oat+field pea ( Medicago sativa L., Avena sativa L., and Pisum sativum L.), hay, and then corn]. This places both organic systems with higher returns than any of the Midwestern standards of no-till corn-soybean, continuous corn, or intensive alfalfa production. Also, the results indicate how risk exposure varied across systems. Interestingly, taking risk into consideration did not drastically affect the ranking among those systems. Our analysis shows that, under the market scenarios that prevailed between 1993 and 2006, intensive rotational grazing and organic grain and forage systems were the most profitable systems on highly productive land in southern Wisconsin.
  • Authors:
    • Ahendsen, B. L.
    • Dixon, B. L.
    • Chavez, E. C.
    • Wailes, E. J.
  • Source: University of Arkansas Department of Agricultural Economics and Agribusiness Staff Papers
  • Issue: 2
  • Year: 2009
  • Summary: This study presents and analyzes the mean financial characteristics of different types of crop and livestock farms in the U.S. in 2005. The eighteen farm types are: poultry, beef cattle, hogs, dairy, general livestock, general cash grain, wheat, corn, soybean, grain sorghum, rice, tobacco, cotton, peanut, general crop, fruits and tree nuts, vegetables, and nursery and greenhouse. Significant, two-way statistical differences in mean farm income statement and farm balance sheet variables are highlighted. Results provide a general indication of the comparative profitability, liquidity, solvency, and financial efficiency of different types of U. S. crop and livestock farms.
  • Authors:
    • Buschman, L. L.
    • French, B. W.
    • Currie, R. S.
    • Davis, H. N.
  • Source: Southwestern Entomologist
  • Volume: 34
  • Issue: 1
  • Year: 2009
  • Summary: This study examined how land management practices can affect the abundance of several arthropods commonly found in agriculture. This work was done in plots that had been subjected to three successive years of an agronomic experiment that evaluated the effects of a wheat, Triticum aestivum L., cover crop or no cover crop on weed and water management. After the third growing season, pitfall traps were installed and arthropods were collected and identified. At one location, carabids (Coleoptera: Carabidae) were identified to genus. Four of the genera ( Amara, Anisodactylus, Harpalus, and Calathus) were more common under no-till conditions. Only one genus ( Stenolophus) was more common in tilled plots. Five genera ( Amara, Bradycellus, Scarites, Stenolophus, and Calathus) were more common in plots with a history of more weeds caused by less herbicide use. Carabids were not more abundant in plots with fewer weeds after herbicides had been applied. Past presence of a winter cover crop never reduced carabid numbers, but significantly increased members of two genera ( Harpalus and Poecilus). As a group, carabids at one location were more common in plots without a history of a cover crop. At another location, more carabids were in tilled than nontilled plots. Crickets (Orthoptera: Gryllidae) were more common under no-till conditions. At all locations, wolf spiders (Araneae: Lycosidae) were more common in plots with no tillage and a previous cover crop. Results suggested that surface residues affected carabids, wolf spiders, and crickets.
  • Authors:
    • Miyao, G.
    • Jackson, J.
    • Mitchell, J. P.
    • Horwath, W. R.
    • Doane, T. A.
    • Brittan, K.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 85
  • Issue: 3
  • Year: 2009
  • Summary: In spite of potential benefits and positive assessments of reducing primary tillage operations, only a small part of irrigated row crops is currently managed using reduced tillage, for reasons that include concerns about its agronomic suitability for certain crop rotations. Three years of a tomato/corn rotation under standard and no-tillage management were used to understand the fate of a fertilizer and cover crop nitrogen (N) application. Uptake of both inputs was reduced under no-tillage during the year of application, in this case a tomato crop. As a result, more input N was retained in the soil in this system. The initial challenge of reduced tomato yields diminished as no-tillage management remained in place and the soil N reservoir developed. Corn production was not affected by tillage treatment. Inclusion of a legume cover crop increased the amount of fertilizer N retained in the soil over time, more so under no-tillage than under standard tillage, emphasizing the benefit of cover crops in reducing the amount of fertilizer required to maintain productivity. While acceptance of reduced tillage ultimately depends on economic performance, the results of this study support its agronomic viability for irrigated row crops.
  • Authors:
    • Drinkwater, L. E.
    • Gardner, J. B.
  • Source: Ecological Applications
  • Volume: 19
  • Issue: 8
  • Year: 2009
  • Summary: Intensively managed grain farms are saturated with large inputs of nitrogen (N) fertilizer, leading to N losses and environmental degradation. Despite decades of research directed toward reducing N losses from agroecosystems, progress has been minimal, and the currently promoted best management practices are not necessarily the most effective. We investigated the fate of N additions to temperate grain agroecosystems using a meta-analysis of 217 field-scale studies that followed the stable isotope N-15 in crops and soil. We compared management practices that alter inorganic fertilizer additions, such as application timing or reduced N fertilizer rates, to practices that re-couple the biogeochemical cycles of carbon (C) and N, such as organic N sources and diversified crop rotations, and analyzed the following response variables: N-15 recovery in crops, total recovery of N-15 in crops and soil, and crop yield. More of the literature (94%) emphasized crop recovery of N-15 than total N-15 recovery in crops and soil (58%), though total recovery is a more ecologically appropriate indicator for assessing N losses. Findings show wide differences in the ability of management practices to improve N use efficiency. Practices that aimed to increase crop uptake of commercial fertilizer had a lower impact on total N-15 recovery (3-21% increase) than practices that re-coupled C and N cycling (30-42% increase). A majority of studies (66%) were only one growing season long, which poses a particular problem when organic N sources are used because crops recover N from these sources over several years. These short-term studies neglect significant ecological processes that occur over longer time scales. Field-scale mass balance calculations using the N-15 data set show that, on average, 43 kg N.ha(-1).yr(-1) was unaccounted for at the end of one growing season out of 114 kg N.ha(-1).yr(-1), representing similar to 38% of the total N-15 applied. This comprehensive assessment of stable-isotope research on agroecosystem N management can inform the development of policies to mitigate nonpoint source pollution. Nitrogen management practices that most effectively increase N retention are not currently being promoted and are rare on the landscape in the United States.
  • Authors:
    • Gerpen, J. H. van
    • Kinney, A. J.
    • Schweiger, B.
    • Tat, M.
    • Tenopir, P.
    • LaVallee, B. J.
    • Graef, G.
    • Clemente, T. E.
  • Source: Plant Biotechnology Journal
  • Volume: 7
  • Issue: 5
  • Year: 2009
  • Summary: Phenotypic characterization of soybean event 335-13, which possesses oil with an increased oleic acid content (>85%) and reduced palmitic acid content (
  • Authors:
    • Kpomblekou-A, K.
    • Hamido, S. A.
  • Source: Soil & Tillage Research
  • Volume: 105
  • Issue: 2
  • Year: 2009
  • Summary: Increasing numbers of vegetable growers are adopting conservation tillage practices and including cover crops into crop rotations. The practice helps to increase or maintain an adequate level of soil organic matter and improves vegetable yields. The effects of the practices, however, on enzyme activities in southeastern soils of the United States have not been well documented. Thus, the objectives of the study were to investigate the effects of cover crops and two tillage systems on soil enzyme activity profiles following tomato and to establish relationships between enzyme activities and soil organic carbon (C) and nitrogen (N). The cover crops planted late in fall 2005 included black oat (Avena strigosa), crimson clover (Trifolium incarnatum L.), or crimson clover-black oat mixed. A weed control (no cover crop) was also included. Early in spring 2006, the plots were disk plowed and incorporated into soil (conventional tillage) or mowed and left on the soil surface (no-till). Broiler litter as source of N fertilizer was applied at a rate of 4.6 Mg ha(-1), triple super phosphate at 79.0 kg P ha(-1), and potassium chloride at 100 kg K ha(-1) were also applied according to soil testing recommendations. Tomato seedlings were transplanted and grown for 60 days on a Marvyn sandy loam soil (fine-loamy, kaolinitic, thermic Typic Kanhapludults). Ninety-six core soil samples were collected at incremental depths (0-5, 5-10, and 10-15 cm) and passed through a 2-mm sieve and kept moist to study arylamidase (EC 3.4.11.2), L-asparaginase (EC 3.5.1.1), L-glutaminase (EC 3.5.1.2), and urease (EC 3.5.1.5) activities. Tillage systems affected only L-glutaminase activity in soil while cover crops affected activities of all the enzymes studied with the exception of urease. The research clearly demonstrated that in till and no-till systems, L-asparaginase activity is greater (P