• Authors:
    • Schimel, D. S.
    • Peterson, G. A.
    • Mosier, A.
    • Parton, W.
    • Ojima, D.
    • Del Grosso, S.
  • Source: Environmental Pollution
  • Volume: 116
  • Issue: Supplement 1
  • Year: 2002
  • Summary: We present evidence to show that DAYCENT can reliably simulate soil C levels, crop yields, and annual trace gas fluxes for various soils. DAYCENT was applied to compare the net greenhouse gas fluxes for soils under different land uses. To calculate net greenhouse gas flux we accounted for changes in soil organic C, the C equivalents of N2O emissions and CH4 uptake, and the CO2 costs of N fertilizer production. Model results and data show that dryland soils that are depleted of C due to conventional till winter wheat/fallow cropping can store C upon conversion to no till, by reducing the fallow period, or by reversion to native vegetation. However, model results suggest that dryland agricultural soils will still be net sources of greenhouse gases although the magnitude of the source can be significantly reduced and yields can be increased upon conversion to no till annual cropping. (C) 2001 Elsevier Science Ltd. All rights reserved.
  • Authors:
    • Follett, R. F.
    • Paustian, K.
    • Sperow, M.
    • Eve, M. D.
  • Source: Environmental Pollution
  • Volume: 116
  • Issue: 3
  • Year: 2002
  • Summary: Average annual net change in soil carbon stocks under past and current management is needed as part of national reporting of greenhouse gas emissions and to evaluate the potential for soils as sinks to mitigate increasing atmospheric CO2. We estimated net soil C stock changes for US agricultural soils during the period from 1982 to 1997 using the IPCC (Intergovernmental Panel on Climate Change) method for greenhouse gas inventories. Land use data from the NRI (National Resources Inventory; USDA-NRCS) were used as input along with ancillary data sets on climate, soils, and agricultural management. Our results show that, overall, changes in land use and agricultural management have resulted in a net gain of 21.2 MMT C year-1 in US agricultural soils during this period. Cropped lands account for 15.1 MMT C year-1, while grazing land soil C increased 6.1 MMT C year-1. The land use and management changes that have contributed the most to increasing soil C during this period are (1) adoption of conservation tillage practices on cropland, (2) enrollment of cropland in the Conservation Reserve Program, and (3) cropping intensification that has resulted in reduced use of bare fallow.
  • Authors:
    • Cross, A. F.
    • Engle, D. M.
    • Tunnell, T. R.
    • Zhang, H.
    • Fuhlendorf, S. D.
  • Source: Restoration Ecology
  • Volume: 10
  • Issue: 2
  • Year: 2002
  • Summary: A comparative analysis of soils and vegetation from cultivated areas reseeded to native grasses and native prairies that have not been cultivated was conducted to evaluate restoration of southern mixed prairie of the Great Plains over the past 30 to 50 years. Restored sites were within large tracts of native prairie and part of long-term grazing intensity treatments (heavy, moderate, and ungrazed), allowing evaluation of the effects of grazing intensity on prairie restoration. Our objective was to evaluate restored and native sites subjected to heavy and moderate grazing regimes to determine if soil nutrients from reseeded cultivated land recovered after 30 years of management similar to the surrounding prairie and to identify the interactive influence of different levels of grazing and history of cultivation on plant functional group composition and soils in mixed prairies. For this mixed prairie, soil nitrogen and soil carbon on previously cultivated sites was 30 to 40% lower than in uncultivated native prairies, indicating that soils from restored sites have not recovered over the past 30 to 50 years. In addition, it appears that grazing alters the extent of recovery of these grassland soils as indicated by the significant interaction between grazing intensity and cultivation history for soil nitrogen and soil carbon. Management of livestock grazing is likely a critical factor in determining the potential restoration of mixed prairies. Heavy grazing on restored prairies reduces the rate of soil nutrient and organic matter accumulation. These effects are largely due to changes in composition (reduced tallgrasses), reduced litter accumulation, and high cover of bare ground in heavily grazed restored prairies. However, it is evident from this study that regardless of grazing intensity, restoration of native prairie soils requires many decades and possibly external inputs to adequately restore organic matter, soil carbon, and soil nitrogen.
  • Authors:
    • Tibke, G. L.
    • Skidmore, E. L.
    • Huang, X.
  • Source: Journal of Soil and Water Conservation
  • Volume: 57
  • Issue: 6
  • Year: 2002
  • Summary: Achieving and maintaining a good soil quality is essential for sustaining agricultural production in an economically viable and environmentally safe manner. The transition of land management provides an opportunity to measure soil-quality indicators to quantify the effects of those management practices. This study compared soil chemical and physical properties after io years of grass on Conservation Reserve Program (CRP) land with those in continuously cropped land (CCL). The sample sites, located in central Kansas, have two mapping units, Harney silt loam (fine, montmorillonitic, mesic Typic Arigiustolls) and Naron fine sandy loam (fine-loamy, mixed, thermic Udic Argiustolls). Soil samples were collected at two depth increments, 0 to 5 cm and 5 to 10 cm. Soil-quality indicators measured were soil acidity (pH), exchangeable cations, nutrients, total carbon, structure, and aggregation. Soil pH was significantly lower in CCL than in CRR Soil total C and N in the surface layer (0 to 5 cm) was much greater than in the deeper layer (5 to 10 cm) in the CRP site. The mass of total carbon of Naron soil was significantly higher for 0 to 5 cm and lower for 5 to io cm depth in CRP land than in CCL. However, the mass of total carbon of Harney soil was significantly higher in no-tilled CCL than in CRP. Bulk density significantly increased in CCL. Based on dry and wet aggregate stability analysis, the results indicated that CRP land had a greater resistance to erosion by both water and wind than CCL. The improvements in soil quality resulting from CRP included reducing soil acidification, alleviating compaction, and reducing topsoil susceptibility to erosion. However, when CRP was taken out for crop production with conventional tillage, total carbon in the surface layer (0 to 5cm) and aggregate stability gradually decreased. This suggested that appropriate land management practices are needed to extend residual benefit from CRP on soil quality.
  • Authors:
    • Smith, P.
    • Williams, S.
    • Schuler, J.
    • Killian, K.
    • Moore, R.
    • Foulk, R.
    • Easter, M.
    • Cipra, J.
    • Bluhm, G.
    • Paustian, K.
    • Brenner, J.
  • Source: Report to the Nebraska Conservation Partnership
  • Year: 2002
  • Summary: Land managers have long known the importance of soil organic matter in maintaining the productivity and sustainability of agricultural land. More recently, interest has developed in the potential for using agricultural soils to sequester C and mitigate increasing atmospheric carbon dioxide by adopting practices that increase standing stocks of carbon in soil organic matter and vegetation. Practices that increase the amount of CO2 taken up by plants (through photosynthesis), which then enter the soil as plant residues, tend to increase soil C stocks. Likewise, management practices that reduce the rate of decay or "turnover" of organic matter in soils will also tend to increase carbon stocks.
  • Authors:
    • Ulmer, M. G.
    • Cihacek, L. J.
  • Source: Agriculture Practices and Policies for Carbon Sequestration in Soil
  • Year: 2002
  • Summary: from summary: "The significance of soils in sequestering greenhouse gases and reducing global warming may be greater due to C sequestration as inorganic C. Soil IC is a sink for atmospheric CO 2 , which may be more resistant to cropping and tillage effects on sequestered soil C and is likely to persist for decades and perhaps centuries after sequestration."
  • Authors:
    • Riedell, W. E.
    • Pikul, J. L.
    • Archer, D. W.
  • Source: Soil & Tillage Research
  • Volume: 67
  • Issue: 1
  • Year: 2002
  • Summary: Ridge tillage (RT) has been proposed as an economically viable conservation tillage alternative for row crop production; however the long-term economic viability of RT in the northern Corn Belt of the USA is largely unknown. Economic returns, risk and input use were compared for RT and conventional tillage (CT) in a corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) rotation with high, medium and low nitrogen treatments. The analysis was based on 10 years of experimental data from Brookings, SD on a Barnes clay loam (US soil taxonomy: fine-loamy, mixed, superactive, frigid Calcic Hapludoll; FAO classification: Chernozem). Economic returns were significantly higher at the highest nitrogen treatment levels. Highest average net returns to land and management were $ 78 per hectare for RT at the high nitrogen treatment level (RT-H) followed by $ 59 per hectare for CT at the high nitrogen treatment level (CT-H). Risk, measured as the standard deviation of net returns, was the lowest for CT at the medium nitrogen treatment level (CT-M) followed by RT-H and CT-H. However, net returns were substantially lower under CT-M at $ 32 per hectare. Average yields and average operating costs were not significantly different for RT-H and CT-H. Reduced equipment operating costs for CT-H were offset by increased herbicide costs for RT-H. Equipment ownership costs were significantly lower for RT-H than CT-H. There were no significant differences in fertilizer use for RT and CT. Pesticide use was significantly higher for RT-H than CT-H. Fuel use was 18-22% lower and labor use was 24-27% lower for RT-H than CT-H. Despite continued low adoption rates for RT in the northern Corn Belt, our analysis shows that RT is an economically viable alternative to CT.
  • Authors:
    • Rice, CW
  • Source: Geotimes
  • Volume: 47
  • Issue: 1
  • Year: 2002
  • Authors:
    • Nielsen, G.
    • Mortensen, D.
    • McGinn, S.
    • Coen, G.
    • Caprio, J.
    • Waltman, S.
    • Padbury, G.
    • Sinclair, R.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 2
  • Year: 2002
  • Summary: The northern Great Plains have long been dominated by conventional tillage systems and cereal-based rotations including summer fallow. Over the last decade, however, the use of conservation tillage systems has markedly increased and, through improved moisture storage, has provided an opportunity for more diversified extended rotations including oilseed, pulse, and forage crops throughout the region. Considerable research is being carried out to assess the adaptability of these new crops and to develop appropriate management strategies. Typically, this type of agronomic research is carried out at plot-sized research sites, with the findings then being extrapolated to surrounding regions where growing conditions are thought to be reasonably similar. Because the environment itself largely dictates the success of a particular cropping system, extrapolation requires knowledge of the environmental conditions of the region and, in particular, the interaction of environmental components of soil and climate in relation to specific crop requirements. This paper describes 14 agroecoregions in the northern Great Plains and provides an initial framework for extrapolating agronomic information at broad regional scales. Because climate is the dominant crop production factor in the region, most of the agroecosystems represent broad climatic zones. Each agroecoregion is described in terms of its soil and landscape characteristics, with a particular focus being given to likely key environmental parameters related to the production of the new oilseed, pulse, and forage crops being introduced in the region.
  • Authors:
    • Thompson, C.
  • Source: Journal of Soil and Water Conservation
  • Volume: 56
  • Issue: 1
  • Year: 2001
  • Summary: A 24 year study of five cropping systems was conducted to determine how 1.) cropping systems, 2.) depth of soil water at planting, and 3.) tillage systems affected yields and economic returns. The study involved two crops, winter wheat (Triticum aestivum L.) and grain sorghum (Sorghum biocolor L Moench), in systems of continuous wheat (WWW), continuous sorghum (SSS), wheat/sorghum/fallow (WSF), wheat/fallow (WF), and sorghum/fallow (SF). These systems were farmed under reduced-till (RT) and no-till (NT) on a nearly level, high fertility, Crete silty clay loam soil (fine, smectitic, mesic Pachic Argiustolls) at the Kansas State University Agricultural Research Center-Hays. Depth of soil water at planting had significant effects on yields of all cropping/tillage systems. Tillage systems had limited effects on wheat yield, but significant effects on sorghum yields. Considering all factors, SSS with RT had the highest economic return on this upland fertile soil in the central Great Plains.