• Authors:
    • Wu, J. J.
  • Source: American Journal of Agricultural Economics
  • Volume: 82
  • Issue: 4
  • Year: 2000
  • Summary: Each year, billions of dollars of public funds are expended to purchase conservation easements on farmland. One unintended impact of these programs is that they may bring non-cropland into crop production. Such a slippage effect can be caused by increased output prices and by substitution effects. This article shows that for each one hundred acres of cropland retired under the Conservation Reserve Program (CRP) in the central United States, twenty acres of non-cropland were converted to cropland. offsetting 9% and 14% of CRP water and wind erosion reduction benefits, respectively. Implications of these results for the design of conservation programs are discussed.
  • Authors:
    • Hulugalle, N. R.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 31
  • Issue: 5-6
  • Year: 2000
  • Authors:
    • Kwon, K. C.
    • Post, W. M.
  • Source: Global Change Biology
  • Volume: 6
  • Issue: 3
  • Year: 2000
  • Summary: When agricultural land is no longer used for cultivation and allowed to revert to natural vegetation or replanted to perennial vegetation, soil organic carbon can accumulate. This accumulation process essentially reverses some of the effects responsible for soil organic carbon losses from when the land was converted from perennial vegetation. We discuss the essential elements of what is known about soil organic matter dynamics that may result in enhanced soil carbon sequestration with changes in land-use and soil management. We review literature that reports changes in soil organic carbon after changes in land-use that favour carbon accumulation. This data summary provides a guide to approximate rates of SOC sequestration that are possible with management, and indicates the relative importance of some factors that influence the rates of organic carbon sequestration in soil. There is a large variation in the length of time for and the rate at which carbon may accumulate in soil, related to the productivity of the recovering vegetation, physical and biological conditions in the soil, and the past history of soil organic carbon inputs and physical disturbance. Maximum rates of C accumulation during the early aggrading stage of perennial vegetation growth, while substantial, are usually much less than 100 g C m-2 y-1. Average rates of accumulation are similar for forest or grassland establishment: 33.8 g C m-2 y-1 and 33.2 g C m-2 y-1, respectively. These observed rates of soil organic C accumulation, when combined with the small amount of land area involved, are insufficient to account for a significant fraction of the missing C in the global carbon cycle as accumulating in the soils of formerly agricultural land.
  • Authors:
    • Raper, R. L.
    • Runion, G. B.
    • Reeves, D. W.
    • Reicosky, D. C.
    • Prior, S. A.
  • Source: Soil & Tillage Research
  • Volume: 54
  • Issue: 3-4
  • Year: 2000
  • Summary: Recent research indicates tillage operations result in a rapid physical release of CO2 and water vapor from soil. However, effects of soil disturbance on gas fluxes during planting operations have not been adequately explored. Our objective was to measure short-term gas loss resulting from the use of different planting preparation implements on long-term residue-covered soil (no-till) on a Norfolk loamy sand (Typic Kandiudults; FAO classification Luxic Ferralsols) in east-central Alabama, USA. A crimson clover (Trifolium incarnatum L.) cover crop was killed with herbicide two weeks prior to the study. Due to dry soil conditions, 15 mm of water was applied 24 h prior to study. Gas fluxes were measured with a large canopy chamber (centered over two rows) for an integrated assessment of equipment-induced soil disturbance. Increased losses of CO2 and water vapor were directly related to increases in soil disturbance. Although these short-term C losses are minor in terms of predicting longterm C turnover in agro-ecosystems, results suggest that selecting planting equipment that maintains surface residue and minimizes soil disturbance could help to conserve soil water needed for successful seedling establishment in these coarse textured soils. Published by Elsevier Science B.V.
  • Authors:
    • Rhoton, F. E.
  • Source: Soil Science Society of America Journal
  • Volume: 64
  • Issue: 2
  • Year: 2000
  • Summary: The number of growing seasons required for no-till practices to improve soil properties should be considered before changing management systems. To evaluate this time factor, an 8-yr tillage study was conducted on a Grenada silt loam (fine-silty, mixed, active, thermic Glossic Fragiudalfs) using cotton (Gossypium hirsutum L.), grain sorghum [Sorghum bicolor (L.) Moench]-corn (Zea mays L.), and soybean [Glycine max (L.) Merr.]-wheat (Triticum aestivum L.) as test crops. Soil samples were characterized for soil organic matter (SOM), pH, exchangeable Ca and Mg, extractable P, K, Fe, Mn, Cu, and Zn, aggregate stability (AS), water dispersible clay (WDC), total clay (TC), and modulus of rupture (MR) at time 0, 4, and 8 yr. Within 4 yr, no-till (NT) resulted in statistically significant (P less than or equal to 0.05) differences compared to conventional tillage (CT). The surface 2.5 cm of the NT treatments had higher levels of SOM, exchangeable Ca, and extractable P, Mn, and Zn, but lower extractable K, Fe, and Cu. Tillage had no effect on exchangeable Mg and pH. No-till also resulted in higher AS, and lower MR, WDC, and TC in the top 2.5 cm, relative to CT. The differences in soil properties between tillage treatments were essentially independent of crop. Instead, the results are controlled by relative amounts of SOM and clay, and the extent to which these properties change with time. Undoubtedly, NT practices ran improve several fertility and erodibility-related properties of this soil within 4 yr, and-enhance its sustainability.
  • Authors:
    • TCG
    • Teasdale,John R.
    • Rosecrance,R. C.
    • Coffman,Charles B.
    • Starr,J. L.
    • Paltineanu,I. C.
    • Lu,Y. C.
    • Watkins,B. K.
  • Source: American Journal of Alternative Agriculture
  • Volume: 15
  • Issue: 2
  • Year: 2000
  • Summary: Sustainable production systems are needed to maintain soil resources and reduce environmental contamination on erodible lands that are incompatible with tillage-intensive operation. A long-term cropping systems comparison was established at Beltsville, Maryland, on a site with 2 to 15% slope to evaluate the efficacy of sustainable strategies compatible with reduced-tillage systems. All systems followed a 2-year rotation of corn the first year and winter wheat followed by soybean the second year. Treatments included (1) no-tillage system with recomended fertilizer and herbicide inputs, (2) crownvetch living mulch system with similar inputs to the no-tillages system, (3) cover crop system including a hairy vetch cover crop before corn and a wheat cover crop before soybean with reduced fertilizer and herbicide inputs, (4) manure systemd including crimson clover green manure plus cow manure for nutrient sources, chisel plow/disk for incorporatin manure and rotary hoe plus cultication for weed control. Results from the initial 4 years demonstrated the relative productivity of these systems. Corn yields were similar in the no-tillage and cover crop systems in each year. both systems average 7.8 Mg ha-1 compared to 5.7 Mg ha-1 in both the croen vetch and manure systems. Wheat yields were highest in the manure system in the first 2 years and in the crown vetch system in the last 2 years. Soybean yields were highest in the cover crop system in all years. The manure system usually had lower yields than the highest yielding system, partly because of competitions from uncontrolled weeds. Several measures of the efficience of grain production were evaluated. The no-tillage system produced the most grain per total vegetative biomass throughout the rotation. The cover crop system produced the most grain per unit of external N input and, along with the no-tillage system, had the highest corn water-use efficiency. The cover crop system also recycled the most vegetative residues and nutrients of all systems. No single system perfomed best according to all measures of comparison, suggesting that trade-offs will be required when choosing production systems.
  • Authors:
    • Wilkinson, S. R.
    • Schomberg, H. H.
    • Stuedemann, J. A.
    • Franzluebbers, A. J.
  • Source: Soil Biology and Biochemistry
  • Volume: 32
  • Issue: 4
  • Year: 2000
  • Summary: Soil organic matter pools under contrasting long-term management systems provide insight into potentials for sequestering oil C, sustaining soil fertility and functioning of the soil±atmospheric interface. We compared soil C and N pools (total, articulate and microbial) under pastures (1) varying due to harvest technique (grazing or haying), species composition (cool- or arm-season), stand age and previous land use and (2) in comparison with other land uses. Grazed tall fescue-common ermudagrass pasture (20 yr old) had greater soil organic C (31%), total N (34%), particulate organic C (66%), articulate organic N (2.4 fold) and soil microbial biomass C (28%) at a depth of 0±200 mm than adjacent land in conservation-tillage cropland (24 yr old). Soil organic C and total N at a depth of 0±200 mm averaged 3800 and 294 g m-2 , respectively, under grazed bermudagrass and 3112 and 219 g m-2, respectively, under hayed bermudagrass. A chronosequence of grazed tall fescue suggested soil organic N sequestration rates of 7.3, 4.4 and 0.6 g m-2 yr-1 to a depth of 200 mm during 0±10, 10±30 and 30±50 yr, respectively. Soil C storage under long-term grazed tall fescue was 85 to 88% of that under forest, whereas soil N storage was 77 to 90% greater under grazed tall fescue than under forest. Properly grazed pastures in the Southern Piedmont USA have great potential to restore natural soil fertility, sequester soil organic C and N and increase soil biological activity.
  • Authors:
    • Stuedemann, J. A.
    • Wright, S. F.
    • Franzluebbers, A. J.
  • Source: Soil Science Society of America Journal
  • Volume: 64
  • Issue: 3
  • Year: 2000
  • Authors:
    • Adkins, W.
    • West, L. T.
    • Kissel, D. E.
    • Chen, F.
  • Source: Soil Science Society of America Journal
  • Volume: 64
  • Issue: 2
  • Year: 2000
  • Summary: The surface soil organic C (SOC) concentration is a useful soil property to map soils, interpret soil properties, and guide fertilizer and agricultural chemical applications. The objective of this study was to determine whether surface SOC concentrations could be predicted from remotely sensed imagery (an aerial photograph of bare surface soil) of a 115-ha field located in Crisp County, Georgia. The surface SOC concentrations were determined for soil samples taken at 28 field locations. The statistical relationship between surface SOC concentrations and image intensity values in the red, green, and blue bands was fit to a to a logarithm linear equation (R2 = 0.93). The distribution of the surface SOC concentrations was predicted with two approaches. The first approach was to apply the relationship to individual pixels and then determine the distribution; the second approach was to classify the image and then apply the relationship to determine the class boundaries and means. Eight levels of surface SOC concentrations were classified in both approaches, and there was good agreement between the two approaches with a probability value near one using a paired t-test. The predicted and measured surface SOC concentrations, based on additional soil samples from 31 field locations, were compared using linear regression (r 2 = 0.97 and r 2=0.98 for the two approaches). The surface SOC concentrations were correctly classified in 77.4 and 74.2% of cases for the two approaches. The procedures tested were accurate enough to be used for precision farming applications in agricultural fields.
  • Authors:
    • Watanabe, T.
    • Tsuruta, H.
    • Akiyama, H.
  • Source: Chemosphere - Global Change Science
  • Volume: 2
  • Issue: 3
  • Year: 2000
  • Summary: Three nitrogen chemical fertilizers were applied to soil - controlled-release urea (CU), a mixture of ammonium sulfate and urea with nitrification inhibitor (AM), and a mixture of ammonium sulfate and urea with no nitrification inhibitor (UA). N2O and NO fluxes from an Andosol soil in Japan were measured six times a day for three months with an automated flux monitoring system in lysimeters. The total amount of nitrogen applied was 20 g N m-2. The total N2O emissions from CU, AM and UA were 1.90, 12.7, and 16.4 mg N m-2, respectively. The total NO emissions from CU, AM and UA were 231, 152, and 238 mg N m-2, respectively. The total NO emission was 12-15 times higher than the total N2O emission. High peaks in N2O and NO emissions from UA occurred for one month after the basal fertilizer application. The N2O emissions from CU and AM during the peak period were 50% of those from UA, and the NO emissions were less than 50% of those from UA. After the peak period, the N2O and NO emissions from CU were the highest for two months. A negative correlation was found between the flux ratio of NO-N to N2O-N and the water-filled pore space. A diel pattern with increased N2O and NO fluxes during the day and with decreased fluxes during the night was observed.