• Authors:
    • Ali, M. K.
    • Paustian, K.
    • Capalbo, S. M.
    • Antle, J. M.
  • Source: Climatic Change
  • Volume: 80
  • Issue: 1-2
  • Year: 2007
  • Summary: The purpose of this paper is to develop and apply a new method to assess economic potential for agricultural greenhouse gas mitigation. This method uses secondary economic data and conventional econometric production models, combined with estimates of soil carbon stocks derived from biophysical simulation models such as Century, to construct economic simulation models that estimate economic potential for carbon sequestration. Using this method, simulations for the central United States show that reduction in fallow and conservation tillage adoption in the wheat-pasture system could generate up to about 1.7 million MgC/yr, whereas increased adoption of conservation tillage in the corn-soy-feed system could generate up to about 6.2 million MgC/yr at a price of $200/MgC. About half of this potential could be achieved at relatively low carbon prices (in the range of $50 per ton). The model used in this analysis produced estimates of economic potential for soil carbon sequestration potential similar to results produced by much more data-intensive, field-scale models, suggesting that this simpler, aggregate modeling approach can produce credible estimates of soil carbon sequestration potential. Carbon rates were found to vary substantially over the region. Using average carbon rates for the region, the model produced carbon sequestration estimates within about 10% of those based on county-specific carbon rates, suggesting that effects of spatial heterogeneity in carbon rates may average out over a large region such as the central United States. However, the average carbon rates produced large prediction errors for individual counties, showing that estimates of carbon rates do need to be matched to the spatial scale of analysis. Transaction costs were found to have a potentially important impact on soil carbon supply at low carbon prices, particularly when carbon rates are low, but this effect diminishes as carbon prices increase.
  • Authors:
    • Gracia, R.
    • Lopez, M.
    • Arrue, J.
    • Moret, D.
  • Source: European Journal of Agronomy
  • Volume: 26
  • Issue: 1
  • Year: 2007
  • Summary: Winter barley is the major crop on semiarid drylands in central Aragon (NE Spain). In this study we compared, under both continuous cropping (BC) (5-6-month fallow) and a crop-fallow rotation (BF) (16-18-month fallow), the effects of three fallow management treatments (conventional tillage, CT; reduced tillage, RT; no-tillage, NT) on the growth, yield and water use efficiency (WUE) of winter barley during three consecutive growing seasons in the 1999-2002 period. Daily precipitation measurements and monthly measurements of soil water storage to a depth of 0.7 m were used to calculate crop water use (ET) and its components. The average growing season precipitation was 195 mm. Above-ground dry matter (DM) and corresponding WUE were high in years with high effective rainfalls (>10 mm day -1) either in autumn or spring. However, the highest values of WUE for grain yield were mainly produced by effective rainfalls during the time from stem elongation to harvest. Despite the similarity in ET for the three tillage treatments, NT provided the lowest DM production, corresponding to a higher soil water loss by evaporation and lower crop transpiration ( T), indicated by the lowest T/ET ratio values found under this treatment. No clear differences in crop yield were observed among the tillage treatments in the study period. On average, and regardless of the type of tillage, BF provided the highest values of DM and WUE and yielded 49% more grain than BC. These differences between cropping systems increased when water-limiting conditions occurred in the early stages of crop growth, probably due to the additional soil water storage under BF at sowing. Although no significant differences in precipitation use efficiency (PUE) were observed between BC and BF, PUE was higher under the BC system, which yielded 34% more grain than the BF rotation when yields were adjusted to an annual basis including the length of the fallow. The crop yield under BF was not dependent on the increase in soil water storage at the end of the long fallow. In conclusion, this study has shown that, although conventional tillage can be substituted by reduced or no-tillage systems for fallow management in semiarid dryland cereal production areas in central Aragon, the practice of long-fallowing to increase the cereal crop yields is not longer sustainable.
  • Authors:
    • Burmester, C.
    • Reeves, D. W.
    • Motta, A. C. V.
    • Feng, Y.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 38
  • Issue: 19-20
  • Year: 2007
  • Summary: The impact of conservation tillage, crop rotation, and cover cropping on soil-quality indicators was evaluated in a long-term experiment for cotton. Compared to conventional-tillage cotton, other treatments had 3.4 to 7.7 Mg ha(-1) more carbon (C) over all soil depths. The particulate organic matter C (POMc) accounts for 29 to 48 and 16 to 22% of soil organic C (SOC) for the 0- to 3- and 3- to 6-cm depths, respectively. Tillage had a strongth influence on POMc within the 0- to 3-cm depth, but cropping intensity and cover crop did not affect POW A large stratification for microbial biomass was observed varing from 221 to 434 and 63 to 110 mg kg(-1) within depth of 0-3 and 12-24 cm respectively. The microbial biomass is a more sensitive indicator (compared to SOC) of management impacts, showing clear effect of tillage, rotation, and cropping intensity. The no-tillage cotton double-cropped wheat/soybean system that combined high cropping intensity and crop rotation provided the best soil quality.
  • Authors:
    • Schomberg, H. H.
    • Franzluebbers, A. J.
    • Endale, D. M.
  • Source: Soil & Tillage Research
  • Volume: 96
  • Issue: 1/2
  • Year: 2007
  • Summary: The type of conservation-tillage management employed could impact surface-soil properties, which could subsequently affect relationships between soil and water quality, as well as with soil C sequestration and greenhouse gas emissions. We determined soil bulk density, organic C and N fractions, plant-available N, and extractable P on Typic Kanhapludults throughout a 7-year period, in which four long-term (>10 years), no-tillage (NT) water catchments (1.3-2.7 ha each) were divided into two treatments: (1) continuation of NT and (2) paraplowing (PP) in autumn (a form of non-inversion deep ripping) with NT planting. Both summer [cotton ( Gossypium hirsutum L.), maize ( Zea mays L.), sorghum ( Sorghum bicolor L. Moench), soybean ( Glycine max L. Merr.)] and winter [wheat ( Triticum aestivum L.), barley ( Hordeum vulgare L.), rye ( Secale cereale L.), crimson clover ( Trifolium incarnatum L.)] crops were NT planted throughout the study under each management system. Soil bulk density was reduced with PP compared with NT by as much as 0.15 Mg m -3, but the extent of reduction was inversely related to the time lag between PP operation and sampling event. Soil organic C became significantly enriched with time during this study under NT (0.49 Mg C ha -1 year -1), but not under PP, in which poultry litter was applied equivalent to 5.7 Mg ha -1 year -1 to all water catchments. Soil maintained a highly stratified depth distribution of organic C and N fractions and extractable P under both NT and PP. Inability to perform the PP operation in the last year of this study resulted in rapid convergence of soil bulk density between tillage systems, suggesting that PP had
  • Authors:
    • Kahlown, M. A.
    • Azam, M.
    • Kemper, W. D.
  • Source: Journal of Soil and Water Conservation
  • Volume: 61
  • Issue: 1
  • Year: 2006
  • Summary: Conventional management practices for the rice-wheat rotation in Pakistan's Punjab have failed to improve crop yield, increase water and fertilizer use efficiencies, and decrease production costs enough to meet an ever-increasing food demand. New technologies such as no-till, laser leveling, and bed and furrow irrigation are being rapidly adopted by the farming community, but without adequate scientific information. Therefore, those practices were evaluated on 71 farms within four representative sites. Land preparation/sowing costs, water savings, use of fertilizers, soil salinity, and crop yield were evaluated. Land preparation and sowing cost on no-till fields was significantly less than on tilled fields. Highest yields were obtained on laser-leveled fields, followed by no-till, bed and furrow fields. Water and nitrogen use efficiencies were much higher on fields with bed and furrow irrigation as compared to the conventional fields. Although the new technologies were economically feasible, we conclude that no-till was the best option for the farmers.
  • Authors:
    • Pala, M.
  • Source: Options Mediterraneennes. Serie A, Seminaires Mediterraneens
  • Issue: 69
  • Year: 2006
  • Summary: The past several decades have witnessed a change from traditional to more intensive agriculture in dryland farming systems of West Asia and North Africa and also in the transitional period of Central Asia and Caucasus (CAC). These two areas can be combined and called the Central and West Asia and North Africa (CWANA) region, which covers diverse agroecological conditions from mild lowlands (Syria) to cold continental (CAC) and cold highlands (Turkey). This region is a major area of the world where drought invariably limits crop production in approximately 1.7 million ha arable land. Agriculture is primarily based on rainfed cropping during the relatively cooler late autumn to early spring as rainfall ranged generally between 200 to 600 mm per year. Dryland crops are mainly wheat, food legumes such as lentil, chickpea, faba beans, and forage legumes such as vetch, medics and lathyrus. Increasing human and livestock population has led desertification and soil degradation in the region. This has led also ICARDA to an assessment of tillage systems for efficiency, enhanced productivity and sustainability of the various farming system changes through a series of long-term trials in the mid 1980s at ICARDA headquarter as well as in the National Agricultural Research Services in close collaboration. Results at ICARDA and the region support a preference for the conservation tillage system (minimum tillage) over deep tillage systems on the grounds of both energy-use efficiency and increased net revenue as direct benefits to livelihood of the rural population. However, whenever available and tested and adopted by farmers with their participatory evaluation as in Central Asia, no-till direct drilling would increase soil organic matter from approximately 0.9% to 1.3% at 0-10 cm top soil and sustain the systems productivity in the long-run on the basis of the initial research results throughout the CWANA region.
  • Authors:
    • Wang, X.
  • Source: Conservation tillage and nutrient management in dryland farming in China
  • Year: 2006
  • Summary: This thesis contains 8 chapters focusing on the relations between rainfall and crop yields, and on the effects of various tillage and nutrient management practices on erosion, crop yields and water and nutrient use efficiencies. The bases of the study were: desk studies on conservation tillage and on dust storm erosion in China; long-term field experiments conducted in the dry semi-humid region of northern China (Shanxi and Henan); and simulation modelling. The first two chapters provide a brief introduction and background information on the trends in soil conservation and conservation tillage practices on global, national and regional scales, with emphasis on dryland farming of northern China. Chapter 3 analyses the effects of variation in rainfall on crop yields. The next chapter covers tillage and residue effects on rainfed wheat and maize production. Chapters 5 and 6 discuss nutrient dynamics in dryland maize cropping systems with emphasis on grain yield, and water and nutrient use efficiencies and on nutrient balances and soil fertility indices. Chapter 7 presents a scenario analysis of tillage, crop residue, cattle manure and fertilizer application management effects on soil organic carbon dynamics, using the Century model with input from the long-term field studies. The final chapter provides a general discussion and synthesis of the research findings. The consequences for future research and application of conservation tillage are also discussed.
  • Authors:
    • Spokas, K. A.
    • Dolan, M. S.
    • Baker, J. M.
    • Venterea, R. T.
  • Source: Soil Science Society of America Journal
  • Volume: 70
  • Issue: 5
  • Year: 2006
  • Summary: Few studies have examined the impacts of rotational tillage regimes on soil carbon (C) and nitrogen (N). We measured the C and N content of soils managed under corn (Zea mays L.)-soybean (Glycine max L.) rotation following 10 and 15 yr of treatments. A conventional tillage (CT) regime employing moldboard and chisel plowing in alternate years was compared with both continuous no-till (NT) and biennial tillage (BT), which employed chisel plowing before soybean only. While masses of C and N in the upper 0.3 m under both BT and NT were higher than CT, only the BT treatment differed from CT when the entire sampled depth (0.6 m) was considered. Decreased C inputs, as indicated by reduced grain yields, may have limited C storage in the NT system. Thus, while more C was apparently retained under NT per unit of C input, some tillage appears necessary in this climate and cropping system to maximize C storage. Soil carbon dioxide (CO2) fluxes under NT were greater than CT during a drier than normal year, suggesting that C storage may also be partly constrained under NT due to wetter conditions that promote increased soil respiration. Increased temperature sensitivity of soil respiration with increasing soil moisture was also observed. These findings indicate that long-term biennial chisel plowing for corn-soybean in the upper mid-west USA can enhance C storage, reduce tillage-related fuel costs, and maintain yields compared with more intensive annual tillage.
  • Authors:
    • Rochette, P.
    • Pattey, E.
    • Newlands, N.
    • McAllister, T. A.
    • McGinn, S. M.
    • Masse, D.
    • Lemke, R.
    • Helgason, B. L.
    • Gregorich, E. G.
    • Gibb, D. J.
    • Ellert, B. H.
    • Dyer, J. A.
    • Desjardins, R. L.
    • Bolinder, M.
    • Boehm, M.
    • Angers, D. A.
    • Janzen, H. H.
    • Smith, W.
    • VandenBygaart, A. J.
    • Wang, H.
  • Source: Canadian Journal of Soil Science
  • Volume: 86
  • Issue: 3
  • Year: 2006
  • Summary: Greenhouse gas emissions from farms can be suppressed in two ways: by curtailing the release of these gases (especially N2O and CH4), and by storing more carbon in soils, thereby removing atmospheric COT But most practices have multiple interactive effects on emissions throughout a farm. We describe an approach for identifying practices that best reduce net, whole-farm emissions. We propose to develop a "Virtual Farm", a series of interconnected algorithms that predict net emissions from flows of carbon, nitrogen, and energy. The Virtual Farm would consist of three elements: descriptors, which characterize the farm; algorithms, which calculate emissions from components of the farm; and an integrator, which links the algorithms to each other and the descriptors, generating whole-farm estimates. Ideally, the Virtual Farm will be: boundary-explicit, with single farms as the fundamental unit; adaptable to diverse farm types; modular in design; simple and transparent; dependent on minimal, attainable inputs; internally consistent; compatible with models developed elsewhere; and dynamic ("seeing" into the past and the future). The Virtual Farm would be constructed via two parallel streams - measurement and modeling - conducted iteratively. The understanding built into the Virtual Farm may eventually be applied to issues beyond greenhouse gas mitigation.
  • Authors:
    • Wilhelm, W. W.
    • Archer, D.
    • Allmaras, R. R.
    • Reicosky, D. C.
    • Johnson, J. M. F.
  • Source: Journal of Soil and Water Conservation
  • Volume: 61
  • Issue: 4
  • Year: 2006
  • Summary: SUMMARY: We still need an answer to the critical question: ˜How much crop biomass is needed to protect and maintain the soil resource, and correspondingly, how much can be harvested as renewable fuel? Through photosynthesis and the processes of growth and translocation, plants use solar energy to transform carbon dioxide and water into grain and biomass.The latter is useful for nurturing the soil biology, maintaining soil properties important in soil quality, and also as a bioenergy feedstock. A practical compromise is needed for crop biomass to function effectively in the competing roles of soil conservation and renewable energy production. Economics and government policy will drive development of biomass for biofuel industries. However, we cannot afford to overlook the potential costs associated with wide-scale removal of crop residues from the land.These costs may not be readily apparent in the short term and economic impacts are not easily quantified. Thus far, farmers are not compensated based on the ecosystem services provided by agricultural watersheds. We suggest a cautious approach to harvesting crop biomass for energy until science-based research provides answers and guidance to the critical questions of how much,when, and where to harvest crop biomass. Research is needed to provide land managers, the biomass industry, and action agencies with sound, scientifically based, field-tested guidelines for sustainable production and harvest of crop residues. This need is especially critical in light of the current economic pressures to find alternative energy sources and the short time-frame set by DOE for domestic renewable fuels to become a significant contributor to the nation's energy and product supply. As the biomass energy industry develops, we strongly encourage soil and energy conservation to achieve sustainable energy security.