541. Orchard floor preparation did not affect early peach tree performance on Aura sandy loam soil.

• Authors:
  • Lokaj, G. R. W.
  • Majek, B. A.
  • Belding, R. D.
  • Hammerstedt, J.
  • Ayeni, A. O.
• Source: HortTechnology
• Volume: 13
• Issue: 2
• Year: 2003
• Summary: Peach ( Prunus persica cv. Candor) trees were established and grown from 1996 to 1999 at the Rutgers Agricultural Research and Extension Center, Bridgeton, New Jersey, USA, to compare their performance under four methods of orchard floor preparation: flat no-till, flat cultivated, mound unmulched, and mound mulched orchard floors. The experimental site was flat and the soil was a well-drained Aura gravelly sandy loam (61% sand, 31% silt and 8% clay) with a pH of 6.5, cation exchange capacity of 5.7, and organic matter content of 2.0%. Soil moisture holding capacity and gas exchange capacity determine the efficacy of mounding in peach orchards. Under these conditions, the method of orchard floor preparation had no effect on peach tree trunk cross-sectional area, fruit number per tree, fruit size and yield. Thus, without irrigation, there was no advantage to the early performance of peach trees associated with orchard floor mounding on Aura gravelly sandy loam when situated on a flat terrain.

542. Soil organic carbon sequestration rates by tillage and crop rotation

• Authors:
  • Post, W. M.
  • West, T. O.
• Source: Soil Science Society of America Journal
• Volume: 66
• Issue: 6
• Year: 2002
• Summary: Changes agricultural management can potentially increase the accumulation rate of soil organic C (SOC), thereby sequestering CO2 from the atmosphere. This study was conducted to quantify potential soil C sequestration rates for different crops in response to decreasing tillage intensity or enhancing rotation complexity, and to estimate the duration of time over which sequestration may occur. Analyses of C sequestration rates were completed using a global database of 67 long-term agricultural experiments, consisting of 276 paired treatments. Results indicate, on average, that a change from conventional tillage (CT) to no-till (NT) can sequester 57 +/- 14 g C m(-2) yr(-1), excluding wheat (Triticum aestivum L.)-fallow systems which may not result in SOC accumulation with a change from CT to NT. Enhancing rotation complexity can sequester an average 20 +/- 12 g C m(-2) yr(-1), excluding a change from continuous corn (Zea mays L.) to corn-soybean (Glycine mar L.) which may not result in a significant accumulation of SOC. Carbon sequestration rates, with a change from CT to NT, can be expected to peak in 5 to 10 yr with SOC reaching a new equilibrium in 15 to 20 yr. Following initiation of an enhancement in rotation complexity, SOC may reach a new equilibrium in approximately 40 to 60 yr. Carbon sequestration rates, estimated for a number of individual crops and crop rotations in this study, can be used in spatial modeling analyses to more accurately predict regional, national, and global C sequestration potentials.

543. Tillage method and crop diversification: Effect on economic returns and riskiness of cropping systems in a thin black chernozem of the Canadian Prairies

• Authors:
  • Campbell, C. A.
  • Derksen, D. A.
  • Lafond, G. P.
  • Zentner, R. P.
• Source: Soil & Tillage Research
• Volume: 67
• Issue: 1
• Year: 2002

544. Five years of Bt cotton in China - the benefits continue

• Authors:
  • Rozelle, S.
  • Hu, R.
  • Huang, J.
  • Pray, C. E.
• Source: The Plant Journal
• Volume: 31
• Issue: 4
• Year: 2002
• Summary: Bt cotton is spreading very rapidly in China, in response to demand from farmers for technology that will reduce both the cost of pesticide applications and exposure to pesticides, and will free up time for other tasks. Based on surveys of hundreds of farmers in the Yellow River cotton-growing region in northern China in 1999, 2000 and 2001, over 4 million smallholders have been able to increase yield per hectare, and reduce pesticide costs, time spent spraying dangerous pesticides, and illnesses due to pesticide poisoning. The expansion of this cost-saving technology is increasing the supply of cotton and pushing down the price, but prices are still sufficiently high for adopters of Bt cotton to make substantial gains in net income.

545. Indiana Carbon Storage Project: Quantifying the change in greenhouse gas emissions due to natural resource conservation practice application in Iowa

• Authors:
  • Williams, S.
  • Schuler, J.
  • Lamm, D.
  • Killian, K.
  • Elliott, T.
  • Easter, M.
  • Cipra, J.
  • Bluhm, G.
  • Paustian, K.
  • Brenner, J.
  • Smith, P.
• 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.

546. Mid-infrared and near-infrared reflectance spectroscopy for soil carbon measurement

• Authors:
  • Kimble, J.
  • Follett, R. F.
  • Reeves, V. B.
  • Reeves, J. B.
  • McCarty, G. W.
• Source: Soil Science Society of America Journal
• Volume: 66
• Issue: 2
• Year: 2002
• Summary: The ability to inventory soil C on landscapes is limited by the ability to rapidly measure soil C. Diffuse reflectance spectroscopic analysis in the near-infrared (NIR, 400-2500 nm) and mid-infrared (MIR, 2500-25 000 nm) regions provides means for measurement of soil C. To assess the utility of spectroscopy for soil C analysis, we compared the ability to obtain information from these spectral regions to quantify total, organic, and inorganic C in samples representing 14 soil series collected over a large region in the west central United States. The soils temperature regimes ranged from thermic to frigid and the soil moisture regimes from udic to aridic. The soils ranged considerably in organic (0.23-98 g C kg-1) and inorganic C content (0.0-65.4 g CO3-C kg-1). These soil samples were analyzed with and without an acid treatment for removal of CO3. Both spectral regions contained substantial information on organic and inorganic C in soils studied and MIR analysis substantially outperformed NIR. The superior performance of the MIR region likely reflects higher quality of information for soil C in this region. The spectral signature of inorganic C was very strong relative to soil organic C. The presence of CO3- reduced ability to quantify organic C using MIR as indicated by improved ability to measure organic C in acidified soil samples. The ability of MIR spectroscopy to quantify C in diverse soils collected over a large geographic region indicated that regional calibrations are feasible.

547. Simulated effects of dryland cropping intensification on soil organic matter and greenhouse gas exchanges using the DAYCENT ecosystem model

• 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.

548. Assessment of a method to measure temporal change in soil carbon storage

• Authors:
  • Entz, T.
  • Janzen, H. Henry
  • Ellert, B. H.
• Source: Soil Science Society of America Journal
• Volume: 66
• Issue: 5
• Year: 2002
• Summary: Sensitive methods are essential to resolve small changes in soil C storage, such as those attained in sequestration projects, against much larger quantities of C already present. To measure temporal changes in C storage we proposed a high-resolution method based on collecting volumetric soil cores from a microsite (4 by 7 m), marking core locations to intersperse multiple cores collected initially and in a subsequent sampling year, rigorous analytical quality control, and calculating soil C pool sizes with proper corrections for unequal soil masses. To evaluate the method, we measured the recovery of 3.64 Mg C ha(-1) added as coal dust to microsites. We calculated C stored in successive soil layers of both fixed volume and equivalent mass. We inferred coal C recovery from spatial comparisons between coal-amended and unamended plots, and from temporal comparisons between soil samples collected before and after coal addition. The comparisons among C storage showed effective recovery of added coal C, but only for paired temporal differences based on calculations of organic C storage in an equivalent soil mass. With spatial comparisons, coal C became undetectable when soil thickness exceeded 35 cm. With temporal comparisons, coal C recovery ranged from 91 to 106%, provided differences were calculated for successively thicker layers of equivalent soil mass. In contrast, recovery was only 64 to 82% when temporal differences were calculated for layers of fixed soil volume. The method is useful to quantify small temporal changes in soil organic C storage within microsites, and possibly over more extensive areas with sufficient samples to characterize spatial variability.

549. Management of irrigated agriculture to increase organic carbon storage in soils

• Authors:
  • Shewmaker, G. E.
  • Sojka, R. E.
  • Entry, J. A.
• Source: Soil Science Society of America Journal
• Volume: 66
• Issue: 6
• Year: 2002
• Summary: Increasing the amount of C in soils may be one method to reduce the concentration of CO2 in the atmosphere. We measured organic C stored in southern Idaho soils having long term cropping histories that supported native sagebrush vegetation (NSB), irrigated mold-board plowed crops (IMP), irrigated conservation-chisel-tilled crops (ICT), and irrigated pasture systems (IP). The CO2 emitted as a result of fertilizer production, farm operations, and CO2 lost via dissolved carbonate in irrigation water, over a 30-yr period was included. Net organic C in ecosystems decreased in the order IP>ICT>NSB>IMP. In this study if NSB were converted to IMP, 0.15 g C m-2 would be emitted to the atmosphere, but if convered to IP 3.56 g C m-2 could be sequestered. If IMP land were converted to ICT, 0.95 g C m-2 could be sequestered in soil and if converted to IP 3.71 g C m-2 could be sequestered. There are 2.6 x 10 ^8 ha of land worldwide presently irrigated. If irrigated ariculture were expanded 10% and the same amount of rainfed land were converted back to native grassland, an increase of 3.4 x 10^9 Mg C (5.9% of the total C emitted in the next 30 yr) could potentially be sequestered. The total projected release of CO2 is 5.7x 10^10 Mg C worldwide during the next 30 yr/ Converting rainfed agriculture back to native vegetation while modestly increasing areas in irrigated agriculture could have a significant impact on CO2 atmospheric concentrations while maintaining or increasing food production.

550. National-scale estimation of changes in soil carbon stocks on agricultural lands

• 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.