• 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.
  • Authors:
    • Wuest, S. B.
  • Source: Applied Soil Ecology
  • Volume: 18
  • Issue: 2
  • Year: 2001
  • Summary: Dryland fanning in the Mediterranean climate of the Pacific Northwest, USA supports extremely low earthworm populations under conventional tillage. Increases in earthworm populations are being observed in fields under no-till cropping systems. A 30+ year experiment with four tillage levels in a pea (Pisum sativum L.)-winter wheat (Triticum aestivum L.) rotation was evaluated for earthworm populations and ponded infiltration rates. Where tillage has been limited to 2.5 cm depth, Apporectodea trapezoides (Duges) mean population was 25 m(-2). Plots subject to tillage by plow (25 cm depth) or chisel (35 cm depth) averaged less than 4 earthworms m-2. The shallow tillage treatment also had the highest average infiltration rate of 70 mm h(-1) compared to 36 for chisel, 27 for spring plow, and 19 mm h(-1) for fall plow treatments. The highly variable nature of earthworm counts and infiltration measurements prevented conclusive correlation between the two, but increases in both can be attributed to minimum tillage.
  • Authors:
    • Cochran,V. L.
    • Thorn,R. G.
    • Shelver,W. L.
    • Caesar-Tonthat,T. C.
  • Source: Applied Soil Ecology
  • Volume: 18
  • Issue: 2
  • Year: 2001
  • Summary: Polyclonal antisera were raised against cell walls of a soil aggregating basidiomycete isolated in eastern Montana (isolate BB1) which has been identified as a member of the russuloid clade using molecular genetic techniques. In cross-reactivity tests using quantitative enzyme-linked immunosorbent assay (ELISA), polyclonal antisera to BB I cross-reacted significantly with fungal species representative of the russuloid clade and little or no reactivity was observed with fungal species of the polyporoid, euagaric, hymenochaetoid, bolete and gomphoid-phalloid clades of the Homobasidiomycetes. These results suggested that the cell walls of fungal species from the russuloid clade share common antigenic binding sites that are recognizable by the polyclonal antibodies and that these sites were not found or were present in small amounts in fungal species from the other clades. Experiments on the water stability of artificial aggregates amended with fungal species representative of these six homobasidiomycete clades indicated that many species of the russuloid clade were very efficient soil stabilizers. Fungal species from the other clades vary in their ability to aggregate soil particles but cross-react weakly with the antibodies. ELISA was used on water stable aggregates (WSA) from soil samples of three dryland locations under conventional tillage, no tillage and fallow management practices and on WSA from soil samples from grass barrier strips that were undisturbed for 30 years. Greater antigenic response was observed from WSA of undisturbed soils compared to cultivated soils and from WSA of soils under no till compared to till or fallow management practices. These results suggested that specific soil aggregating russuloids in WSA are sensitive to soil disturbance such as tillage. To our knowledge, this study is the first report of the detection and quantification of a taxonomic group of specific soil aggregating Homobasidiomycetes in dryland soils under diverse agricultural systems.
  • Authors:
    • Halvorson, A. D.
    • Wienhold, B. J.
    • Black, A. L.
  • Source: Agronomy Journal
  • Volume: 93
  • Issue: 5
  • Year: 2001
  • Summary: Spring wheat (Triticum aestivum L.) is generally produced in the northern Great Plains using tillage and a crop-fallow system. This study evaluated the influence of tillage system [conventional-till (CT), minimum-till (MT), and no-till (NT)] and N fertilizer rate (0, 22, and 45 kg N ha(-1)) on grain N, grain N removal from cropping system, and changes in residual postharvest soil NO3-N during six rotation cycles of a dryland spring wheat-fallow (SW-F) cropping system. Grain N concentration increased vith increasing N rate and was higher with CT (33-3 g kg(-1)) than with NT (32.3 g kg-1) at 45 kg ha(-1) N rate. Grain N removal per crop was greater with CT (70 kg N ha (1)) and MT (68 kg N ha(-1)) than with NT (66 kg N ha (1)) and tended to increase with increasing N rate, but varied with rotation cycle. Total grain N removal in six rotation cycles was in the order: CT > MT > NT. Total grain N removal by six SW crops was increased by N fertilization, with only 21 and 17% of the applied N removed in the grain for the 22 and 45 kg ha(-1) N rates, respectively. Postharvest soil NO3-N levels in the 150-cm profile varied with N rate and rotation cycle, with residual NO3-N increasing during consecutive dry crop cycles. In contrast, some leaching of NO3-N below the SW root zone may have occurred during wetter crop cycles. Soil profile NO3-N levels tended to be greater with CT and MT than with NT. Variation in precipitation during rotation cycles and N fertilization impacted grain N removal and residual soil NO3-N levels more than tillage system within this SW-F cropping system.
  • Authors:
    • Kling, C. L.
    • Babcock, B. A.
    • Kurkalova, L. A.
    • Pautsch, G. R.
  • Source: Contemporary Economic Policy
  • Volume: 19
  • Issue: 2
  • Year: 2001
  • Summary: Agricultural tillage practices are important human-induced activities that can alter carbon emissions from agricultural soils and have the potential to contribute significantly to reductions in greenhouse gas emission (Lal et al., The Potential of U.S. Cropland, 1998). This research investigates the expected costs of sequestering carbon in agricultural soils under different subsidy and market-based policies. Using detailed National Resources Inventory data, we estimate the probability that farmers adopt conservation tillage practices based on a variety of exogenous characteristics and profit from conventional practices. These estimates are used with physical models of carbon sequestration to estimate the subsidy costs of achieving increased carbon sequestration with alternative subsidy schemes.
  • Authors:
    • Ball, A.
    • Pretty, J.
  • Year: 2001
  • Authors:
    • Grant, B.
    • Desjardins, R. L.
    • Smith, W. N.
  • Source: Canadian Journal of Soil Science
  • Volume: 81
  • Issue: 2
  • Year: 2001
  • Summary: The Century model was used to estimate the influence of changing agricultural practices on C levels in seven major soil groups in Canada for the years from 2000 to 2010. Conversion of arable land to permanent cover, and inclusion of forages in crop rotations would result in the greatest sequestration of C, averaging 0.62 and 0.44 Mg C ha-1 yr-1, respectively. The increase in soil C when conventional-tillage is converted to no-tillage management was estimated to average about 0.13 Mg C ha-1 yr-1. Reduction of summerfallow (wheat-fallow to wheat-wheat-fallow) in the arid and semi-arid chernozems of Western Canada would reduce C losses by about 0.03 Mg C ha-1 yr-1. If fertilizer use efficiency was increased by 50%, 0.04 Mg C ha-1 yr-1 would be sequestered, whereas a decrease of 50% in fertilizer use efficiency would result in a loss of 0.05 Mg C ha-1 yr-1. Timing of N application (fall vs. spring) had little effect on C change. This study indicates that there are several feasible techniques that could be adopted by agricultural producers in Canada that would significantly increase CO2 uptake from the atmosphere. Although our estimates are based on changes in individual management options, we recognize that producers are likely to adopt several options at the same time. Any interactions resulting from such a move have not been assessed in this analysis, in particular the impact on N2O emissions. Key words: Soil carbon, CO2, C sequestration, Century model, soil, tillage, agricultural practices, nitrous oxide emissions, crop rotations
  • Authors:
    • Follett, R. F.
  • Source: Soil & Tillage Research
  • Volume: 61
  • Issue: 1-2
  • Year: 2001
  • Summary: One of the most important terrestrial pools for carbon (C) storage and exchange with atmospheric CO2 is soil organic carbon (SOC). Following the advent of large-scale cultivation, this long-term balance was disrupted and increased amounts of SOC were exposed to oxidation and loss as atmospheric CO2. The result was a dramatic decrease in SOC. If amounts of C entering the soil exceed that lost to the atmosphere by oxidation, SOC increases. Such an increase can result from practices that include improved: (1) tillage management and cropping systems, (2) management to increase amount of land cover, and (3) efficient use of production inputs, e.g. nutrients and water. Among the most important contributors is conservation tillage (i.e., no-till, ridge-till, and mulch-tillage) whereby higher levels of residue cover are maintained than for conventional-tillage. Gains in amount of land area under conservation tillage between 1989 and 1998 are encouraging because of their contributions to soil and water conservation and for their potential to sequester SOC. Other important contributors are crop residue and biomass management and fallow reduction. Collectively, tillage management and cropping systems in the US are estimated to have the potential to sequester 30-105 million metric tons of carbon (MMTC) yr-1. Two important examples of management strategies whereby land cover is increased include crop rotations with winter cover crops and the conservation reserve program (CRP). Such practices enhance SOC sequestration by increasing the amount and time during which the land is covered by growing plants. Crop rotations, winter cover crops, and the CRP combined have the potential to sequester 14-29 MMTC yr-1. Biomass production is increased by efficient use of production inputs. Optimum fertility levels and water availability in soils can directly affect quantity of crop residues produced for return to the soil and for SOC sequestration. Nutrient inputs and supplemental irrigation are estimated to have the potential to sequester 11-30 MMTC yr-1. In the future, it is important to acquire an improved understanding of SOC sequestration processes, the ability to make quantitative estimates of rates of SOC sequestration, and technology to enhance these rates in an energy- and input-efficient manner. Adoption of improved tillage practices and cropping systems, increased land cover, and efficient use of nutrient and water inputs are examples where such information is necessary.
  • Authors:
    • Kascak, C. A.
    • Fuglie, K. O.
  • Source: Applied Economic Perspectives and Policy
  • Volume: 23
  • Issue: 2
  • Year: 2001
  • Summary: A national sample of U.S. farms is used to estimate the long-term trends in adoption and diffusion of conservation tillage, IPM, and soil fertilizer testing, technologies designed to reduce environmental exteralities from agriculture. Results from a duration model show that diffusion of these technologies has been relatively slow, with long lags in adoption due to differences in land quality, farm size, farmer education, and regional factors.
  • Authors:
    • Wagoner, P.
    • Drinkwater, L. E.
    • Douds, D. D.
    • Galvez, L.
  • Source: Plant and Soil
  • Volume: 228
  • Issue: 2
  • Year: 2001
  • Summary: Low-input agricultural systems that do not rely on fertilizers may be more dependent on vesicular-arbuscular mycorrhizal [VAM] fungi than conventionally managed systems. We studied populations of spores of VAM fungi, mycorrhiza formation and nutrient utilization of maize (Zea mays L.) grown in moldboard plowed, chisel-disked or no-tilled soil under conventional and low-input agricultural systems. Maize shoots and roots were collected at four growth stages. Soils under low-input management had higher VAM fungus spore populations than soils under conventional management. Spore populations and colonization of maize roots by VAM fungi were higher in no-tilled than in moldboard plowed or chisel-disked soil. The inoculum potential of soil collected in the autumn was greater for no-till and chisel-disked soils than for moldboard plowed soils and greater for low-input than conventionally farmed soil. The effects of tillage and farming system on N uptake and utilization varied with growth stage of the maize plants. The effect of farming system on P use efficiency was significant at the vegetative stages only, with higher efficiencies in plants under low-input management. The effect of tillage was consistent through all growth stages, with higher P use efficiencies in plants under moldboard plow and chisel-disk than under no-till. Plants grown in no-tilled soils had the highest shoot P concentrations throughout the experiment. This benefit of enhanced VAM fungus colonization, particularly in the low-input system in the absence of effective weed control and with likely lower soil temperatures, did not translate into enhanced growth and yield.