• Authors:
    • NASS
    • USDA
  • Year: 2009
  • Authors:
    • Smith, K. A.
    • Edwards, A. C.
    • Reay, D. S.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 133
  • Issue: 3-4
  • Year: 2009
  • Summary: Direct and indirect nitrous oxide (N2O) emissions and leaching losses from an intensively managed grazed pasture in the Ythan catchment, Aberdeenshire, UK, were measured and compared over a 17-month period. Simultaneous measurements of farm-wide leaching losses of N2O were also made and catchment-wide fluxes were estimated from existing N leaching data. The relative importance of direct and indirect N2O fluxes at the field, farm and catchment scale was then assessed. At the field scale we found that direct N2O emissions were low (1.2 kg N ha-1 year-1, 0.6% of N input) with indirect N2O emissions via drainage waters comprising a significant proportion (25%) of total N2O emissions. At the whole-farmscale, the N2O-N emission factor (0.003) for leached NO3-N (EF5-g) was in line with the IPCC's recent downward revision. At the catchment scale, a direct N2O flux of 1.9 kg N ha-1 year-1 and an indirect flux of 0.06 kg N2O-N ha-1 year-1 were estimated. This study lends further support to the recent downward revision of the IPCC emission factor for N2O arising from leached N in surface and ground waters (EF5-g) and highlights the need for multiple point sampling to ensure that the importance of indirect N2O losses via drainage waters is not misrepresented at the farm and catchment scales.
  • Authors:
    • Grau, R.
    • Baptista, S.
    • Birkenholtz, T.
    • Lambin, E. F.
    • Ickowitz, A.
    • Hecht, S.
    • Geoghegan, J.
    • Lawrence, D.
    • DeFries, R. S.
    • Turner, B. L.
    • Uriarte ,M.
    • Schneider ,L.
    • Rudel, T. K.
  • Source: Proceedings of the National Academy of Sciences of the United States of America
  • Volume: 106
  • Issue: 49
  • Year: 2009
  • Summary: Does the intensification of agriculture reduce cultivated areas and, in so doing, spare some lands by concentrating production on other lands? Such sparing is important for many reasons, among them the enhanced abilities of released lands to sequester carbon and provide other environmental services. Difficulties measuring the extent of spared land make it impossible to investigate fully the hypothesized causal chain from agricultural intensification to declines in cultivated areas and then to increases in spared land. We analyze the historical circumstances in which rising yields have been accompanied by declines in cultivated areas, thereby leading to land-sparing. We use national-level United Nations Food and Agricultural Organization data on trends in cropland from 1970-2005, with particular emphasis on the 1990-2005 period, for 10 major crop types. Cropland has increased more slowly than population during this period, but paired increases in yields and declines in cropland occurred infrequently, both globally and nationally. Agricultural intensification was not generally accompanied by decline or stasis in cropland area at a national scale during this time period, except in countries with grain imports and conservation set-aside programs. Future projections of cropland abandonment and ensuing environmental services cannot be assumed without explicit policy intervention.
  • Authors:
    • Robertson, G. P.
    • Kravchenko, A. N.
    • Basso, B.
    • Senthilkumar, S.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 6
  • Year: 2009
  • Summary: Temporal changes in soil C content vary as a result of complex interactions among different factors including climate, baseline soil C levels, soil texture, and agricultural management practices. The study objectives were: to estimate the changes in soil total C contents that occurred in the past 18 to 21 yr in soils under agricultural management and in never-tilled grassland in southwest Michigan; to explore the relationships between these changes and soil properties, such as baseline C levels and soil texture; and to simulate C changes using a system approach model (SALUS). The data were collected from two long-term experiments established in 1986 and 1988. Georeferenced samples were collected from both experiments before establishment and then were resampled in 2006 and 2007. The studied agricultural treatments included the conventional chisel-plow and no-till management systems with and without N fertilization and the organic chisel-plow management with cover crops. Total C was either lost in the conventional chisel-plowed systems or was only maintained at the 1980s levels by the conservation management systems. The largest loss in the agricultural treatments was 4.5 Mg ha(-1) total C observed in the chisel-plow system without N fertilization. A loss of 17.3 Mg ha(-1) occurred in the virgin grassland sod. Changes in C content tended to be negatively related to baseline C levels. Under no-till, changes in C were positively related to silt + clay contents. The SALUS predictions of soil C changes were in excellent agreement with the observed data for most of the agricultural treatments and for the virgin soil.
  • Authors:
    • Bosque-Pérez, N. A.
    • Eigenbrode, S. D.
    • Hatten, T. D.
    • Johnson-Maynard, J. L.
    • Umiker, K. J.
  • Source: Soil & Tillage Research
  • Volume: 105
  • Issue: 2
  • Year: 2009
  • Summary: Farmers within the Inland Pacific Northwest are gradually transitioning to direct seed (DS) practices that reduce soil disturbance and increase surface residue compared to conventional tillage (CT). Despite this transition the impacts of DS practices on soil properties and fauna in commercial fields has been little studied in the region. During the spring and summer of 2002 and 2003 we compared soil organic carbon (SOC), total nitrogen (TN), pH, and earthworm and cocoon densities in CT and DS fields planted to either spring wheat or pea in the Palouse region of northern Idaho. In 2002 mean SOC within the 0-10-cm depth was greater in DS fields (2.05%) than at the same depth in CT fields (1.79%), however SOC within the 30-40-cm depth was lower under DS compared to CT. Mean soil pH within the 0-10-cm depth was 5.35 under DS and 5.61 under CT indicating that pH stratification can occur when tillage is reduced. Tillage effects on SOC, TN, and pH were not found in 2003. Tillage also did not significantly influence earthworm densities, which averaged 39 individuals m-2 in 2002 and 57 individuals m-2 in 2003. Correlations were detected in 2003 DS fields between soil properties (SOC and TN) and earthworm and cocoon densities at depths above 30 cm while in 2002 correlations in DS fields occurred with cocoon density, but not with earthworm density. Direct seed management can increase near-surface SOC and TN concentrations compared to CT practices, however, SOC concentrations deeper in the soil appear to remain the same or possibly decrease. Higher SOC and TN near the soil surface, as found in DS fields, appear to promote greater earthworm densities, which may improve long-term soil productivity.
  • Authors:
    • Institute for the Study of Earth, Oceans and Space
  • Year: 2009
  • Summary: The DNDC model is a process-base model of carbon (C) and nitrogen (N) biogeochemistry in agricultural ecosystems. This document describes how to use the PC Windows versions of the DNDC model for predicting crop yield, C sequestration, nitrate leaching loss, and emissions of C and N gases in agroecosystems. Part I provides a brief description of the model structure with relevant scientific basis. Part II describes how to install the model. Part III and IV demonstrate how to conduct simulations with the site and regional versions of DNDC, respectively. Part V provides basic information for uncertainty analysis with DNDC. Part VI contains six case studies demonstrating the input procedures for simulating crop yield, soil C dynamics, nitrate leaching loss, and trace gas emissions. A list of relevant publications is included in Part VII. These publications provide more information about the scientific background and applications of DNDC far beyond this User's Guide. DNDC9.3 can run in two modes: site or regional. By selecting the mode, the users will open a corresponding interface to manage their input information for the modeled site or region.
  • Authors:
    • Bashan, Y.
    • Hartmann, A.
  • Source: European Journal of Soil Biology
  • Volume: 45
  • Issue: 1
  • Year: 2009
  • Summary: This special issue contains 15 papers covering topics on: the field performance of a liquid formulation of Azospirillum brasilense on dryland wheat productivity; cadaverine production by A. brasilense and its possible role in plant growth promotion and osmotic stress mitigation; seedlings growth promotion by A. brasilense under normal and drought conditions; the ability of A. brasilense Az39 and Bradyrhizobium japonicum E109, inoculated singly or in combination, to promote seed germination and early seedling growth in maize and soyabean; the effect of Azospirillum inoculation and nitrogen fertilizer application on grain yield and on the diversity of endophytic bacteria in the phyllosphere of rice rainfed crop; the impact of Azospirillum brasilense and Pseudomonas fluorescens inoculation on the wheat yield; the influence of plant growth-promoting microorganisms on the utilization of urea-N and grain yield of paddy rice; the isolation, partial identification and application of diazotrophic rhizobacteria from traditional Indian rice cultivars; stress-responsive indole-3-acetic acid biosynthesis by A. brasilense SM and its ability to modulate plant growth; brominated phenols as auxin-like molecules; the growth promotion effect on the freshwater microalga Chlorella vulgaris by the nitrogen-fixing, plant growth-promoting bacterium Bacillus pumilus; A. brasilense PII proteins GlnB and GlnZ; the structural organization of the glnBA region of the A. brasilense genome; colonization of sugarcane plantlets by mixed inoculations with diazotrophic bacteria; and the diversity of 16S-rRNA and nifH genes derived from rhizosphere soil and roots of the endemic drought tolerant grass Lasiurus scindicus.
  • Authors:
    • Lal, R.
  • Source: Soil & Tillage Research
  • Volume: 102
  • Issue: 2
  • Year: 2009
  • Summary: Global energy demand of 424 EJ year-1 in 2000 is increasing at the rate of 2.2% year-1. There is a strong need to increase biofuel production because of the rising energy costs and the risks of global warming caused by fossil fuel combustion. Biofuels, being C-neutral and renewable energy sources, are an important alternative to fossil fuels. Therefore, identification of viable sources of biofuel feedstock is a high priority. Harvesting lignocellulosic crop residues, especially of cereal crops, is being considered by industry as one of the sources of biofuel feedstocks. Annual production of lignocellulosic residues of cereals is estimated at 367 million Mg year-1 (75% of the total) for the U.S., and 2800 million Mg year-1 (74.6% of the total) for the world. The energy value of the residue is 16 × 106 BTU Mg-1. However, harvesting crop residues would have strong adverse impact on soil quality. Returning crop residues to soil as amendments is essential to: (a) recycling plant nutrients (20-60 kg of N, P, K, Ca per Mg of crop residues) amounting to 118 million Mg of N, P, K in residues produced annually in the world (83.5% of world's fertilizer consumption), (b) sequestering soil C at the rate of 100-1000 kg C ha-1 year-1 depending on soil type and climate with a total potential of 0.6-1.2 Pg C year-1 in world soils, (c) improving soil structure, water retention and transmission properties, (d) enhancing activity and species diversity of soil fauna, (e) improving water infiltration rate, (f) controlling water runoff and minimizing risks of erosion by water and wind, (g) conserving water in the root zone, and (h) sustaining agronomic productivity by decreasing losses and increasing use efficiency of inputs. Thus, harvesting crop residues as biofuel feedstock would jeopardize soil and water resources which are already under great stress. Biofuel feedstock must be produced through biofuel plantations established on specifically identified soils which do not compete with those dedicated to food crop production. Biofuel plantations, comprising of warm season grasses (e.g., switch grass), short rotation woody perennials (e.g., poplar) and herbaceous species (e.g., miscanthus) must be established on agriculturally surplus/marginal soils or degraded/desertified soils. Plantations established on such soils would restore degraded ecosystems, enhance soil/terrestrial C pool, improve water resources and produce biofuel feedstocks.
  • Authors:
    • Baraibar, B.
    • Westerman, P. R.
    • Recasens, J.
  • Source: Journal of Applied Ecology
  • Volume: 46
  • Issue: 2
  • Year: 2009
  • Summary: Agricultural intensification can cause a huge increase in productivity. However, associated costs in terms of reduced, self-regulation and increased reliance on external inputs for the control of pests, diseases and weeds are seldom taken into account or acknowledged. A pro-active approach in which ecosystems services are documented and potential effects of changes in agricultural practices evaluated may lead to more informed decisions prior to implementation. We investigated the effects of management of cereal production in a semi-arid region on weed seed mortality caused by predators. Seed losses have a greater impact on weed population size than any other life cycle process and should therefore be of significance for natural weed control. We hypothesized that the conversion from rain-fed to irrigated production should lead to reduced and the adoption of no-till techniques to increased seed predation. Seed removal and seed predator populations were monitored in irrigated (N = 3) and rain-fed cereal fields (N = 6) and field margins. Of the dryland fields half was conventionally tilled and the other half no-till. Seed removal (g g(-1) 2-days(-1)) was followed from April 2007 until June 2008, using Petri-dishes and exclosure cages. Populations of harvester ants were estimated by direct nest counts; rodent populations by Sherman live traps. Seed removal in dryland cereals, mainly by harvester ants Messor barbarus was high from mid April to mid October, and should cause a strong weed suppressive effect. Seed removal in irrigated cereals, mainly by granivorous rodents Mus spretus, was low. Seed removal was higher in no-till than in conventional fields and corresponded to differences in harvester ant nest densities. Synthesis and applications. Our results show that tillage and irrigation in a semi-arid cereal production system results in a reduction and total annihilation of granivorous harvester ants, respectively. The concurrent decline in weed seed mortality could lead to increased herbicide use and dependency. In particular, in areas where economic margins are small or the environmental costs of tillage and irrigation high, the increased costs of chemical weed control may exceed the benefits. Here, preserving biodiversity to enhance natural weed control is a viable alternative to agricultural intensification.
  • Authors:
    • Jia, L.
    • Raun, W. R.
    • Schroder, J.
    • Zhang, H.
    • Chen, X.
    • Li, R.
    • Cui, Z.
    • Zhang, F.
    • Miao, Y.
    • Li, F.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 5
  • Year: 2009
  • Summary: Optical sensor-based N management strategies are promising approaches to improve N-use efficiency (NUE) and reduce environmental pollution risk. The objective of this study was to evaluate an active optical sensor-based in-season N management strategy for winter wheat (Triticum aestivum L.) in the North China Plain (NCP). Initially, 10 field experiments were conducted at four villages in NCP in the 2004/05, 2005/06, and 2006/07 growing seasons to evaluate the in-season N requirement prediction developed by Oklahoma State University. Then the N application rates, winter wheat grain yield, NUE, economic returns, residual N content after harvest and apparent N loss were compared among three different management systems on a total of 16 farmer fields in 2005/2006 and 14 farmer fields in 2006/2007. The systems included a sensor-based system, a soil test-based approach crediting soil residual mineral N (N-min) to different depth at different growth stages, and common farmer practices. Averaged across site-years, the sensor-based, soil N-min-based N management strategies, and farmer practices produced similar grain yields but used 67, 88, and 372 kg N ha(-1), respectively. Nitrogen-use efficiencies were 61.3, 51.0, and 13.1% for the three methods of N recommendations, correspondingly. Their residual N content in the soil and apparent N loss were 115, 122, and 208 kg N ha(-1), and 4, 15, and 205 kg N ha(-1), respectively. The optical sensor-based N management strategy is relatively easy to use, has better potential to improve NUE and economic returns, and reduces residual soil N content and apparent N loss than other methods currently used in the NCP.