• Authors:
    • Paustian, K.
    • Merckx, R.
    • Six, J.
    • Denef, K.
  • Source: Soil Science Society of America Journal
  • Volume: 68
  • Issue: 6
  • Year: 2004
  • Authors:
    • Verhagen, J.
    • Smith, P.
    • Rounsevell, M. D. A.
    • Freibauer, A.
  • Source: Geoderma
  • Volume: 122
  • Issue: 1
  • Year: 2004
  • Summary: In this review, technical and economically viable potentials for carbon sequestration in the agricultural soils of Europe by 2008-2012 are analysed against a business-as-usual scenario. We provide a quantitative estimation of the carbon absorption potential per hectare and the surface of agricultural land that is available and suitable for the implementation of those measures, their environmental effects as well as the effects on farm income. Realistically, agricultural soils in EU-15 can sequester up to 16-19 Mt C year-1 during the first Kyoto commitment period (2008-2012), which is less than one fifth of the theoretical potential and equivalent to 2% of European anthropogenic emissions. We identified as most promising measures: the promotion of organic inputs on arable land instead of grassland, the introduction of perennials (grasses, trees) on arable set-aside land for conservation or biofuel purposes, to promote organic farming, to raise the water table in farmed peatland, and--with restrictions--zero tillage or conservation tillage. Many options have environmental benefits but some risk of increasing N2O emissions. For most measures it is impossible to determine the overall impact on farm profitability. Efficient carbon sequestration in agricultural soils demands a permanent management change and implementation concepts adjusted to local soil, climate and management features in order to allow selection of areas with high carbon sequestering potential. Some of the present agricultural policy schemes have probably helped to maintain carbon stocks in agricultural soils.
  • Authors:
    • Li, C.
    • Lemke, R. L.
    • Desjardins, R. L.
    • Smith, W. N.
    • Grant, B.
  • Source: Climatic Change
  • Volume: 65
  • Issue: 3
  • Year: 2004
  • Summary: The Denitrification-Decompostion (DNDC) model was used to estimate the impact of change in management practices on N2O emissions in seven major soil regions in Canada, for the period 1970 to 2029. Conversion of cultivated land to permanent grassland would result in the greatest reduction in N2O emissions, particularly in eastern Canada where the model estimated about 60% less N2O emissions for this conversion. About 33% less N2O emissions were predicted for a change from conventional tillage to no-tillage in western Canada, however, a slight increase in N2O emissions was predicted for eastern Canada. Greater N2O emissions in eastern Canada associated with the adoption of no-tillage were attributed to higher soil moisture causing denitrification, whereas the lower emissions in western Canada were attributed to less decomposition of soil organic matter in no-till versus conventional tilled soil. Elimination of summer fallow in a crop rotation resulted in a 9% decrease in N2O emissions, with substantial emissions occurring during the wetter fallow years when N had accumulated. Increasing N-fertilizer application rates by 50% increased average emissions by 32%,while a 50% decrease of N-fertilizer application decreased emissions by16%. In general, a small increase in N2O emissions was predicted when N-fertilizer was applied in the fall rather than in the spring. Previous research on CO2 emissions with the CENTURY model (Smith et al.,2001) allowed the quantification of the combined change in N2O andCO2 emissions in CO2 equivalents for a wide range of management practices in the seven major soil regions in Canada. The management practices that have the greatest potential to reduce the combined N2O and CO2 emissions are conversion from conventional tillage to permanent grassland, reduced tillage, and reduction of summer fallow. The estimated net greenhouse gas (GHG) emission reduction when changing from cultivated land to permanent grassland ranged from 0.97 (Brown Chernozem) to 4.24 MgCO2 equiv. ha-1 y-1 (Black Chernozem) for the seven soil regions examined. When changing from conventional tillage to no-tillage the net GHG emission reduction ranged from 0.33 (Brown Chernozem) to 0.80 Mg CO2 equiv. ha-1 y-1 (Dark Gray Luvisol). Elimination of fallow in the crop rotation lead to an estimated net GHG emission reduction of 0.43 (Brown Chernozem) to 0.80 Mg CO2 equiv.ha-1 y-1 (Dark Brown Chernozem). The addition of 50% more or 50% less N-fertilizer both resulted in slight increases in combined CO2 and N2O emissions. There was a tradeoff in GHG flux with greater N2O emissions and a comparable increase in carbon storage when 50% more N-fertilizer was added. The results from this work indicate that conversion of cultivated land to grassland, the conversion from conventional tillage to no-tillage, and the reduction of summerfallow in crop rotations could substantially increase C sequestration and decrease net GHG emissions. Based on these results a simple scaling-up scenario to derive the possible impacts on Canada's Kyoto commitment has been calculated.
  • Authors:
    • Guzha, A. C.
  • Source: Soil & Tillage Research
  • Volume: 76
  • Issue: 2
  • Year: 2004
  • Summary: Conservation of soil water is an important management objective for crop production in the semi-arid tropics where droughts are persistent. Identification of the best tillage methods to achieve this objective is thus imperative. The integrated effects of conservation tillage on soil micro topography and soil moisture on a sandy loam soil were evaluated. The field experiment consisted of five tillage treatments, namely tied ridging (TR), no till (NT), disc plough (DP), strip catchment tillage (SCT) and hand hoe (HH). Data measured in the field included soil moisture content, surface roughness, infiltration and sorghum grain yield. A depth storage model was used to estimate depression storage TR treatment and the higher the surface roughness, the greater the depression storage volume. Regression analysis showed that random roughness decreased exponentially with increase in cumulative rainfall. Higher moisture contents were associated with treatments having higher depressional storage. Infiltration rate was significantly higher in the tilled soils than the untilled soils. The DP treatment had the highest cumulative infiltration while NT had the lowest. The Infiltration model which was fitted to the infiltration data gave good fit. Grain yield was highest in TR and least in NT, whereas DP and HH had similar yields.
  • Authors:
    • Holland, J. M.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 103
  • Issue: 1
  • Year: 2004
  • Summary: Conservation tillage (CT) is practised on 45 million ha world-wide, predominantly in North and South America but its uptake is also increasing in South Africa, Australia and other semi-arid areas of the world. It is primarily used as a means to protect soils from erosion and compaction, to conserve moisture and reduce production costs. In Europe, the area cultivated using minimum tillage is increasing primarily in an effort to reduce production costs, but also as a way of preventing soil erosion and retain soil moisture. A large proportion (16%) of Europe's cultivated land is also prone to soil degradation but farmers and governments are being slow to recognise and address the problem, despite the widespread environmental problems that can occur when soils become degraded. Conservation tillage can improve soil structure and stability thereby facilitating better drainage and water holding capacity that reduces the extremes of water logging and drought. These improvements to soil structure also reduce the risk of runoff and pollution of surface waters with sediment, pesticides and nutrients. Reducing the intensity of soil cultivation lowers energy consumption and the emission of carbon dioxide, while carbon sequestration is raised though the increase in soil organic matter (SOM). Under conservation tillage, a richer soil biota develops that can improve nutrient recycling and this may also help combat crop pests and diseases. The greater availability of crop residues and weed seeds improves food supplies for insects, birds and small mammals. All these aspects are reviewed but detailed information on the environmental benefits of conservation tillage is sparse and disparate from European studies. No detailed studies have been conducted at the catchment scale in Europe, therefore some findings must be treated with caution until they can be verified at a larger scale and for a greater range of climatic, cropping and soil conditions. (C) 2004 Elsevier B.V. All rights reserved.
  • Authors:
    • Perfect, E.
    • Herbeck, J.
    • Murdock, L.
    • Grove, J. H.
    • Dí­az-Zorita, M.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 6
  • Year: 2004
  • Summary: The development of well-structured soils is a goal for achieving sustainable and productive agricultural systems. Nevertheless, the maintenance of soil structure in continuous no-till (NT) soils has sometimes been thought to induce soil conditions that are detrimental to crop yields. The objectives of this research were to characterize the effects of periodic tillage disruption in otherwise NT systems on soil properties and the yields of winter wheat (Triticum aestivum L.), double-cropped soybean [Glycine max (L.) Merr.], and maize (Zea mays L.) in rotation and to determine if soil structural changes occurring in tilled soils are independent of changes in other soil properties. A field experiment was established in 1992 on a Huntington silt loam soil (Fluventic Hapludoll) at the University of Kentucky Research and Education Center in Princeton (KY) under a NT crop sequence with two seedbed preparation methods for winter wheat, (a) NT or (b) chisel plus disk tillage (Till). In fall 2000, similar soil chemical properties were observed between disrupted and continuous NT systems over the 0- to 20-cm layer. The geometric mean diameter of dry fragments and the soil water content retained between 0.0003 and 0.03 MPa water potential was greater in NT soils than in soils tilled for winter wheat. Tillage for winter wheat enhanced winter wheat yields (4.2% increase), mostly under low-yielding conditions, but it resulted in a reduction of subsequent summer crop yields (i.e., 3.7% for soybean and 7.0% for maize). The yields obtained in our study translate to an economic benefit for the continuous NT system. Net returns per hectare were estimated to be $73 higher for the winter wheat/double-crop soybean-maize rotation under NT than under Till treatments. The differences in maize yields between NT and tilled treatments were attributed to a better water supply in NT soil due to the maintenance of a larger number of mesopores and a great hydraulic conductivity. In the absence of significant changes in other physicochemical properties, periodic tillage appears to disrupt soil structure, which negatively affects crop productivity.
  • Authors:
    • USDA-ARS
    • Clapp, C. E.
    • Linden, D. R.
    • Allmaras, R. R.
  • Source: Soil Science Society of America Journal
  • Volume: 68
  • Issue: 4
  • Year: 2004
  • Summary: Soil organic carbon (SOC) is sensitive to management of tillage, residue (stover) harvest, and N fertilization in corn (Zea mays L.), but little is known about associated root biomass including rhizodeposition. Natural C isotope abundance ({delta}13C) and total C content, measured in paired plots of stover harvest and return were used to estimate corn-derived SOC (cdSOC) and the contribution of nonharvestable biomass (crown, roots, and rhizodeposits) to the SOC pool. Rhizodeposition was estimated for each treatment in a factorial of three tillage treatments (moldboard, MB; chisel, CH; and no-till, NT), two N fertilizer rates (200 and 0 kg N ha-1), and two corn residue managements. Treatments influenced cdSOC across a wide range (6.8-17.8 Mg C ha-1). Nitrogen fertilization increased stover C by 20%, cdSOC by only 1.9 Mg C ha-1, and increased rhizodeposition by at least 110% compared with that with no N fertilizer. Stover harvest vs. stover return reduced total source carbon (SC) by 20%, cdSOC by 35%, and total SOC. The amount of stover source carbon (SSC) responded to tillage (MB > CH > NT), but tillage affected the amount of cdSOC differently (NT > CH > MB). Total SOC was maintained only by both N fertilization and stover return during the 13-yr period. The ratio of SC in the nonharvestable biomass to SSC ranged from 1.01 to 3.49; a ratio of 0.6 conforms to a root-to-shoot ratio of 0.4 when the root biomass includes 50% rhizodeposits. Tillage controlled the fraction of SC retained as cdSOC (i.e., humified; 0.26 for NT and 0.11 for MB and CH), even though N fertilization, stover harvest, and tillage all significantly influenced SC. Decomposition of labile rhizodeposits was a major component of the nonhumified fraction. Rhizodeposition was as much as three times greater than suggested by laboratory and other controlled studies. To understand and manage the entire C cycle, roots and rhizodeposition must be included in the analysis at the field level.
  • Authors:
    • Lindwall, W.
    • Kulshreshtha, S.
    • Desjardins, R.
    • Junkins, B.
    • Boehm, M.
  • Source: Climatic Change
  • Volume: 65
  • Issue: 3
  • Year: 2004
  • Summary: Net greenhouse gas (GHG) emissions from Canadian crop and livestock production were estimated for 1990, 1996 and 2001 and projected to 2008. Net emissions were also estimated for three scenarios (low (L), medium (M) and high (H)) of adoption of sink enhancing practices above the projected 2008 level. Carbon sequestration estimates were based on four sink-enhancing activities: conversion from conventional to zero tillage (ZT), reduced frequency of summerfallow (SF), the conversion of cropland to permanent cover crops (PC), and improved grazing land management (GM). GHG emissions were estimated with the Canadian Economic and Emissions Model for Agriculture (CEEMA). CEEMA estimates levels of production activities within the Canadian agriculture sector and calculates the emissions and removals associated with those levels of activities. The estimates indicate a decline in net emissions from 54 Tg CO2-Eq yr-1 in1990 to 52 Tg CO2-Eq yr-1 in 2008. Adoption of thesink-enhancing practices above the level projected for 2008 resulted in further declines in emissions to 48 Tg CO2-Eq yr-1 (L), 42 TgCO2-Eq yr-1 (M) or 36 Tg CO2-Eq yr-1 (H). Among the sink-enhancing practices, the conversion from conventional tillage to ZT provided the largest C sequestration potential and net reduction in GHG emissions among the scenarios. Although rates of C sequestration were generally higher for conversion of cropland to PC and adoption of improved GM, those scenarios involved smaller areas of land and therefore less C sequestration. Also, increased areas of PC were associated with an increase in livestock numbers and CH4 and N2O emissions from enteric fermentation andmanure, which partially offset the carbon sink. The CEEMA estimates indicate that soil C sinks are a viable option for achieving the UNFCCC objective of protecting and enhancing GHG sinks and reservoirs as a means of reducing GHG emissions (UNFCCC, 1992).
  • Authors:
    • Schoenau, J.
    • Mohr, R.
    • McLaren, D.
    • Irvine, R.
    • Derksen, D.
    • Monreal, M.
    • Grant, C.
  • Source: Better Crops with Plant Food
  • Volume: 88
  • Issue: 2
  • Year: 2004
  • Summary: Field experiments were conducted at the Research Centre and the Zero-Till Farm, Manitoba, Canada, during 1999-2000, 2000-01 and 2001-01, wherein rape and spring wheat were sown using conventional tillage (CT) and no-till (NT) in the first year of study. The crops were supplemented with 0, 22 or 44 lb P 2O 5/acre, side-banded at sowing. After rape and spring wheat harvest, the stubble in the CT plots was tilled. In the second year, flax was sown into both stubbled and tilled plots, and supplemented with P fertilizer side-banded at 0 or 44 lb P 2O 5/acre. The roots were evaluated for mycorrhizal association at 5 weeks of growth and seed yield was collected at crop maturity. The P nutrition of flax was most influenced by the preceding crop in rotation, while tillage system and P fertilizer management had minor impact on flax. Comparative data on the effect of P fertilizer application to current year flax, previous crop type and P fertilizer management, and tillage system on mycorrhiza incidence and flax seed yield are tabulated.
  • Authors:
    • Kreye, H.
  • Source: Bulletin OILB/SROP
  • Volume: 27
  • Issue: 10
  • Year: 2004
  • Summary: In a long-term field trial, the effects of three different tillage systems on harmful organisms and yield were investigated. The focus was on fungal diseases, weeds and slugs. With the ploughing system as the standard, a non-inversion/conservation tillage and a direct drilling/no till system were compared with one another. The crop rotation oilseed rape-wheat-barley, which was established in 1995, was reconverted into a crop rotation oilseed rape-wheat-wheat in 1998 due to problems with volunteer wheat in the following barley in the two ploughless tillage systems. The occurrence of Phoma root-collar and stem disease, the most important in Germany, was not affected in comparison over the years by the intensity of the cultivation. For Sclerotinia stem rot, a correlation could only be determined with the tillage systems in one year of the trial series. The infection became more severe with decreasing intensity of soil cultivation. Whether this result can be reproduced in future growing seasons remains to be seen. Effects on the incidence of Verticillium longisporum could not be determined. Other diseases arose only sporadically at very low levels. However, in comparison, the occurrence of weeds was affected significantly. The amount of grass weed species ( Alopecurus myosuroides, Apera spica-venti, volunteer barley) increased in the systems without ploughing. The effect on dicotyledonous weed species was dependent on the particular species. In individual years, heavy slug damage could be correlated with direct drilling system.