• Authors:
    • Hunt, J. R.
    • Dalgliesh, N. P.
    • McCown, R. L.
    • Whish, J. P. M.
    • Robertson, M. J.
    • Foale, M. A.
    • Poulton, P. L.
    • Rees, H. van
    • Carberry, P. S.
    • Hochman, Z.
  • Source: Crop & Pasture Science
  • Volume: 60
  • Issue: 11
  • Year: 2009
  • Summary: Crop simulation models relevant to real-world agriculture have been a rationale for model development over many years. However, as crop models are generally developed and tested against experimental data and with large systematic gaps often reported between experimental and farmer yields, the relevance of simulated yields to the commercial yields of field crops may be questioned. This is the third paper in a series which describes a substantial effort to deliver model-based decision support to Australian farmers. First, the performance of the cropping systems simulator, APSIM, in simulating commercial crop yields is reported across a range of field crops and agricultural regions. Second, how APSIM is used in gaining farmer credibility for their planning and decision making is described using actual case studies. Information was collated on APSIM performance in simulating the yields of over 700 commercial crops of barley, canola, chickpea, cotton, maize, mungbean, sorghum, sugarcane, and wheat monitored over the period 1992 to 2007 in all cropping regions of Australia. This evidence indicated that APSIM can predict the performance of commercial crops at a level close to that reported for its performance against experimental yields. Importantly, an essential requirement for simulating commercial yields across the Australian dryland cropping regions is to accurately describe the resources available to the crop being simulated, particularly soil water and nitrogen. Five case studies of using APSIM with farmers are described in order to demonstrate how model credibility was gained in the context of each circumstance. The proposed process for creating mutual understanding and credibility involved dealing with immediate questions of the involved farmers, contextualising the simulations to the specific situation in question, providing simulation outputs in an iterative process, and together reviewing the ensuing seasonal results against provided simulations. This paper is distinct from many other reports testing the performance and utility of cropping systems models. Here, the measured yields are from commercial crops not experimental plots and the described applications were from real-life situations identified by farmers. A key conclusion, from 17 years of effort, is the proven ability of APSIM to simulate yields from commercial crops provided soil properties are well characterised. Thus, the ambition of models being relevant to real-world agriculture is indeed attainable, at least in situations where biotic stresses are manageable.
  • Authors:
    • Lal,R.
    • Dubey,A.
  • Source: Journal of Crop Improvement
  • Volume: 23
  • Issue: 4
  • Year: 2009
  • Summary: Sustainability of agricultural systems depends on their carbon (C) footprint, and the C output:C input ratio. Thus, this study was conducted with the objectives to: (i) assess the agricultural C emissions in relation to predominant farming systems in Punjab, India, and Ohio, USA; (ii) evaluate C-use efficiency of production systems; and (iii) determine the relative sustainability of agronomic production systems as determined by their C footprints. The data collated on C-based input into the soil for predominant crops for both regions included the amounts of fertilizers (N, P, K), herbicides and pesticides used for each crop annually, tillage methods, cropland area, total production of each crop, area under different farming systems, water-management practices (e.g., tubewell irrigation), and total number of livestock. These data were used to compute C equivalent (CE) per hectare of input and output, and the relative sustainability indices as a measure of the C-production efficiency. There existed a linear relationship observed between C input and C output for Punjab, indicating that an increase of 1 Tg/yr (1 Tg=teragram=10 12 g=million ton) of C input resulted in the corresponding C output of ~12 Tg/yr. A similar linear relationship between input and net C output between the 1930s and 1980s was observed for Ohio, and the ratio reached a plateau during 1990s. The average C-sustainability index (increase in C output as % of C-based input) value for Ohio from 1990 to 2005 was 35-43, almost 2.5 times that of Punjab. Since 1989, there has been a major shift in Ohio from conventional tillage to reduced and conservation tillage along with a decline in fertilizer use. No-till farming is practiced on about 35% of the cultivated area, which involves elimination of plowing, retention of crop residue mulch, and judicious use of chemicals. In Punjab, crop residues are removed, resulting in loss of C from the soil organic carbon pool. Hence, the C-based sustainability index is much higher in Ohio than in Punjab. C-efficient systems are more sustainable than inefficient farming systems, and residue removal reduces agricultural sustainability by depleting the soil C pool.
  • Authors:
    • Gotosa, J.
    • Gwenzi, W.
    • Chakanetsa, S.
    • Mutema, Z.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 83
  • Issue: 3
  • Year: 2009
  • Summary: In southern Africa, tillage research has focused on rainfed smallholder cropping systems, while literature on high-input irrigated cropping systems is limited. We evaluated the effects of conventional (CT), minimum (MT) and no-till (NT) tillage systems on soil organic carbon (SOC), bulk density, water-stable aggregates (WSA), mean weighted diameter (MWD) and crop yields in an irrigated wheat-cotton rotation. Soil data were monitored in the first and final year, while yields were monitored seasonally. Average bulk densities (1.5-1.7 Mg m -3) were similar among tillage systems, but often exceeded the critical limit (1.60 Mg m -3) for optimum root growth. Conversion from CT to MT and NT failed to ameliorate the high bulk densities associated with the alluvial soil. SOC (g kg -1) at 0-15 cm was higher ( P<0.05) under MT (3.9-5.8) and NT (4.2-5.6) than CT (2.9-3.3). Corresponding horizon SOC stocks (Mg C ha -1) for the tillage treatments were; 9.3-13.9 (MT), 9.3-13.5 (NT) and 7.3-7.7 (CT). In the final year, significant ( P<0.05) tillage effects on SOC stocks were also observed at 15-30 cm. Cumulative SOC stocks (Mg C ha -1) in the 0-60 cm profile were higher ( P<0.05) under MT (32.8-39.9) and NT (32.9-41.6) than CT (27.8-30.9). On average, MT and NT sequestered between 0.55 and 0.78 Mg C ha -1 year -1 at 0-30 cm depth, but a net decline (0.13 Mg C ha -1 year -1) was observed under CT. At 0-30 cm, MT and NT had higher ( P<0.05) MWD (0.19-0.23 mm) and WSA (2.3-3.5%) than CT (MWD: 0.1-0.12 mm, WSA: ~1.0%). Both MWD and WSA were significantly ( P<0.05) correlated to SOC. Seasonal yields showed significant ( P<0.05) tillage effects, but 6-year mean yields (t ha -1) were similar (CT: 4.49, MT: 4.33, NT: 4.32 for wheat; CT: 3.30, MT: 2.82, NT: 2.83 for cotton). Overall, MT and NT improved soil structural stability and carbon sequestration, while impacts on crop productivity were limited. Therefore, MT and NT are more sustainable tillage systems for the semi-arid regions than conventional tillage.
  • Authors:
    • Chang, X. X.
    • Yang, R.
    • Liu, W. J.
    • Su, Y. Z.
  • Source: Environmental Management
  • Volume: 43
  • Issue: 6
  • Year: 2009
  • Summary: Maintenance of soil organic carbon (SOC) is important for sustainable use of soil resources due to the multiple effects of SOC on soil nutrient status and soil structural stability. The objective of this study was to identify the changes in soil aggregate distribution and stability, SOC, and nitrogen (N) concentrations after cropland was converted to perennial alfalfa (Medicago sativa L. Algonguin) grassland for 6 years in the marginal oasis of the middle of Hexi Corridor region, northwest China. Significant changes in the size distribution of dry-sieving aggregates and water-stable aggregates, SOC, and N concentrations occurred after the conversion from crop to alfalfa. SOC and N stocks increased by 20.2% and 18.5%, respectively, and the estimated C and N sequestration rates were 0.4 Mg C ha-1 year-1 and 0.04 Mg N ha-1 year-1 following the conversion. The large aggregate (>5 mm) was the most abundant dry aggregate size fraction in both crop and alfalfa soils, and significant difference in the distribution of dry aggregates between the two land use types occurred only in the >5 mm aggregate fraction. The percentage of water-stable macroaggregates (>2, 2-0.25 mm) and aggregate stability (mean weight diameter of water-stable aggregates, WMWD) were significantly higher in alfalfa soils than in crop soils. There was a significant linear relationship between total SOC concentration and aggregate parameters (mean weight diameter) for alfalfa soils, indicating that aggregate stability was closely associated with increased SOC concentration following the conversion of crops to alfalfa. The SOC and N concentrations and the C/N ratio were greatest in the >2 mm water-stable aggregates and the smallest in the 0.25-0.05 mm aggregates in crop and alfalfa soils. For the same aggregate, SOC and N concentrations in aggregate fractions increased with increasing total SOC and N concentrations. The result showed that the conversion of annual crops to alfalfa in the marginal land with coarse-texture soils can significantly increase SOC and N stocks, and improve soil structure.
  • Authors:
    • Worth, D.
    • Desjardins, R. L.
    • Dyer, J. A.
    • Vergé, X. P. C.
  • Source: Livestock Science
  • Volume: 121
  • Issue: 1
  • Year: 2009
  • Summary: In order to determine the potential of production practices for reducing greenhouse gas (GHG)emissions, it is important to quantify the GHG emissions associated with various types of production. The methodology from the Intergovernmental Panel on Climate Change (IPCC) adjusted for conditions in Canada was used to calculate the GHG emissions from the Canadian pork industry for census years from 1981 to 2001. Emissions of CH4, N2O and CO2 from animals, their facilities and the crops used to feed them were estimated. The Pork Crop Complex (PCC), defined as the area used to grow the crops that feed all Canadian swine, was estimated using the recommended livestock feed rations. Fertilizer application and the use of fossil fuel were down-scaled from the national crop areas to the PCC. This study also estimated the GHG emission intensity based on the total weight of live animal production (destined for either slaughter or export). The growth of the swine population led to an increase in GHG emissions from the pork industry by 54% between 1981 and 2001. The main GHG was CH4, representing about 40% of the 6.7 TgCO2equiv. total in 2001. Nitrous oxide and fossil CO2 both accounted for about 30%. Due to changes in management practices, the GHG emission intensity of the Canadian swine industry decreased from 2.99 to 2.31 kg of CO2equiv. per kg of live market animal during the same period.
  • Authors:
    • Worth, D.
    • Desjardins, R. L.
    • Dyer, J. A.
    • Vergé, X. P. C.
  • Source: The Journal of Applied Poultry Research
  • Volume: 18
  • Issue: 2
  • Year: 2009
  • Summary: As people become more aware of the environmental footprint of different foods, consumers may modify their diets to reduce the impact of their diets on the environment. For this to occur, it is necessary to know the impact that individual food types have on the environment. This publication presents the greenhouse gas (GHG) emissions as well as the GHG emission intensity associated with various types of poultry production in Canada for the census years 1981 to 2006. Greenhouse gas emissions were calculated using the methodology from the Intergovernmental Panel on Climate Change adjusted for conditions in Canada. Direct emissions of CH4, N2O, and CO2 from birds, their facilities, and the avian crop complex, corresponding to the area used to grow the crops that feed Canadian poultry, were estimated using poultry diet surveys. Between 1981 and 2006, because of the strong growth of broiler production, GHG emissions from the poultry industry increased by 40%. The main GHG was N2O, representing approximately 57% of the total emissions. Fossil fuel CO2 accounted for approximately 38%, whereas CH4 accounted for 5%. In western Canada, GHG emission intensities decreased owing to a reduction in the consumption of fossil fuels associated with the adoption of reduced- and no-tillage cropping systems, whereas in eastern Canada, the reduction was due to lower N2O emissions. The emissions of all 3 GHG from turkeys decreased because of the more rapid turnover of a marketable product (shortened life span) in later census years. Compared with other Canadian meat protein commodities in 2001, poultry emitted only 47% as much GHG per unit of live weight as pork and only 10% as much GHG per unit of live weight as beef.
  • Authors:
    • Kleiner, K.
  • Source: Nature Reports Climate Change
  • Volume: 3
  • Year: 2009
  • 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:
    • Moreno, F.
    • Murillo, J. M.
    • López-Garrido, R.
    • Melero, S.
  • Source: Soil & Tillage Research
  • Volume: 104
  • Issue: 2
  • Year: 2009
  • Summary: Short- and long-term field experiments are necessary to provide important information about how soil carbon sequestration is affected by soil tillage system; such systems can also be useful for developing sustainable crop production systems. In this study, we evaluated the short- and long-term effects of conservation tillage (CT) on soil organic carbon fractions and biological properties in a sandy clay loam soil. Both trials consisted of rainfed crop rotation systems (cereal-sunflower-legumes) located in semi-arid SW Spain. In both trials, results were compared to those obtained using traditional tillage (TT). Soil samples were taken in flowering and after harvesting of a pea crop and collected at three depths (0-5, 5-10 and 10-20 cm). The soil organic carbon fractions were measured by the determination of total organic carbon (TOC), active carbon (AC) and water soluble carbon (WSC). Biological status was evaluated by the measurement of soil microbial biomass carbon (MBC) and enzymatic activities [dehydrogenase activity (DHA), o-diphenol oxidase activity (DphOx), and beta-glucosidase activity (beta-glu)]. The contents of AC and MBC in the long-term trial and contents of AC in the short-term trial were higher for CT than TT at 0-5 cm depth for both sampling periods. Furthermore, DHA and beta-glucosidase values in the July sampling were higher in the topsoil under conservation management in both trials (short- and long-term). The parameters studied tended to decrease as depth increased for both tillage system (TT and CT) and in both trials with the exception of the DphOx values, which tended to be higher at deeper layers. Values of DHA and beta-glu presented high correlation coefficients (r from 0.338 to 0.751, p <= 0.01) with AC, WSC and TOC values in the long-term trial. However, there was no correlation between either TOC or MBC and the other parameters in the short-term trial. In general, only stratification ratios of AC were higher in CT than in TT in both trials. The results of this study showed that AC content was the most sensitive and reliable indicator for assessing the impact of different soil management on soil quality in the two experiments (short- and long-term). Conservation management in dryland farming systems improved the quality of soil under our conditions, especially at the surface layers, by enhancing its storage of organic matter and its biological properties, mainly to long-term. (C) 2009 Elsevier B.V. All rights reserved.
  • Authors:
    • Wong, C. P.
    • Neely, C. L.
    • Schohr, T.
    • Oldfield, J. T.
    • Laca, E. A.
    • Kustin, C.
    • George, M. R.
    • Brown, J. R.
    • Alvarez, P.
    • Fynn, A. J.
  • Year: 2009