• Authors:
    • Hepperly, P.
    • LaSalle, T. J.
  • Year: 2008
  • Authors:
    • Furtan, W. H.
    • Davey, K. A.
  • Source: Canadian Journal of Agricultural Economics/Revue Canadienne D'Agroeconomie
  • Volume: 56
  • Issue: 3
  • Year: 2008
  • Summary: The adoption of conservation tillage technology since the 1970s has been one of the most remarkable changes in the production of crops on the Canadian Prairies. The decision whether to adopt conservation tillage technology or not requires the producer to go through a thorough decision-making process. In Canada, there has been little economic research on the question of what farm, regional, and environmental characteristics affect the adoption decision. Using 1991, 1996, and 2001 Census of Agriculture data together with other data sources we estimate a probit model explaining the adoption decision. We find that important variables include farm size, proximity to a research station, type of soil, and weather conditions.
  • Authors:
    • Parton, W. J.
    • Halvorson, A. D.
    • Del Grosso, S. J.
  • Source: Journal of Environmental Quality
  • Volume: 37
  • Year: 2008
  • Summary: Agricultural soils are responsible for the majority of nitrous oxide (N2O) emissions in the USA. Irrigated cropping, particularly in the western USA, is an important source of N2O emissions. However, the impacts of tillage intensity and N fertilizer amount and type have not been extensively studied for irrigated systems. The DAYCENT biogeochemical model was tested using N2O, crop yield, soil N and C, and other data collected from irrigated cropping systems in northeastern Colorado during 2002 to 2006. DAYCENT uses daily weather, soil texture, and land management information to simulate C and N fluxes between the atmosphere, soil, and vegetation. The model properly represented the impacts of tillage intensity and N fertilizer amount on crop yields, soil organic C (SOC), and soil water content. DAYCENT N2O emissions matched the measured data in that simulated emissions increased as N fertilization rates increased and emissions from no-till (NT) tended to be lower on average than conventional-till (CT). However, the model overestimated N2O emissions. Lowering the amount of N2O emitted per unit of N nitrified from 2 to 1% helped improve model fit but the treatments receiving no N fertilizer were still overestimated by more than a factor of 2. Both the model and measurements showed that soil NO3- levels increase with N fertilizer addition and with tillage intensity, but DAYCENT underestimated NO3- levels, particularly for the treatments receiving no N fertilizer. We suggest that DAYCENT could be improved by reducing the background nitrification rate and by accounting for the impact of changes in microbial community structure on denitrification rates.
  • Authors:
    • Plowden, Y.
    • Benham, E. C.
    • Franks, E. C.
    • Salon, P. R.
    • Dell, C. J.
  • Source: Journal of Soil and Water Conservation
  • Volume: 63
  • Issue: 3
  • Year: 2008
  • Summary: No-till (NT) crop production is expected to sequester soil C, but little data is available for dairy forage systems. Our objective was to quantify impacts of NT and rye (Secale cereale L.) cover crops on soil C and N pools and associated soil properties on Pennsylvania dairies. Samples were collected from seven fields following corn harvest. The NT fields had approximately 50% more C and N in particulate and mineral-associated pools in the upper 5 cm (2 in) compared to conventional tillage, but C and N accumulations below 5 cm were similar. This suggests a C sequestration rate of ~0.5 Mg ha-1 y-1 (~0.2 tn ac-1 yr-1) in the 8 to 13 years NT has been used. Soil aggregate stability and cation exchange capacity were proportional to C pool sizes. Rye cover crops had no clear impact. Findings show that expected increases in C sequestration and soil quality with NT can be achieved in dairy forage systems.
  • Authors:
    • Hofman, G.
    • Gabriels, D.
    • De Neve, S.
    • Vandenbruwane, J.
    • Van den Bossche, A.
    • D'Haene, K.
  • Source: Biology and Fertility of Soils
  • Volume: 45
  • Issue: 2
  • Year: 2008
  • Summary: The effect of reduced tillage (RT) on nitrous oxide (N2O) emissions of soils from fields with root crops under a temperate climate was studied. Three silt loam fields under RT agriculture were compared with their respective conventional tillage (CT) field with comparable crop rotation and manure application. Undisturbed soil samples taken in September 2005 and February 2006 were incubated under laboratory conditions for 10 days. The N2O emission of soils taken in September 2005 varied from 50 to 1,095 mu g N kg(-1) dry soil. The N2O emissions of soils from the RT fields taken in September 2005 were statistically (P 0.05) higher or comparable than the N2O emissions from their respective CT soil. The N2O emission of soils taken in February 2006 varied from 0 to 233 mu g N kg(-1) dry soil. The N2O emissions of soils from the RT fields taken in February 2006 tended to be higher than the N2O emissions from their respective CT soil. A positive and significant Pearson correlation of the N2O-N emissions with nitrate nitrogen (NO3--N) content in the soil was found (P 0.01). Leaving the straw on the field, a typical feature of RT, decreased NO3- -N content of the soil and reduced N2O emissions from RT soils.
  • Authors:
    • Wallander, R.
    • Lemke, R. L.
    • Miller, P. R.
    • Engel, R. E.
    • Dusenbury, M. P.
  • Source: Journal of Environmental Quality
  • Volume: 37
  • Issue: 2
  • Year: 2008
  • Summary: Field measurements of N2O emissions from soils are limited for cropping systems in the semiarid northern Great Plains (NGP). The objectives were to develop N2O emission-time profiles for cropping systems in the semiarid NGP, define important periods of loss, determine the impact of best management practices on N2O losses, and estimate direct N fertilizer-induced emissions (FIE). No-till (NT) wheat (Triticum Aestivum L.)-fallow, wheat-wheat, and wheat-pea (Pisum sativum), and conventional till (CT) wheat-fallow, all with three N regimes (200 and 100 kg N ha-1 available N, unfertilized control); plus a perennial grass-alfalfa (Medicago sativa L.) system were sampled over 2 yr using vented chambers. Cumulative 2-yr N2O emissions were modest in contrast to reports from more humid regions. Greatest N2O flux activity occurred following urea-N fertilization (10-wk) and during freeze-thaw cycles. Together these periods comprised up to 84% of the 2-yr total. Nitrification was probably the dominant process responsible for N2O emissions during the post-N fertilization period, while denitrification was more important during freeze-thaw cycles. Cumulative -yr N2O-N losses from fertilized regimes were greater for wheat-wheat (1.31 kg N ha-1) than wheat-fallow (CT and NT) (0.48 kg N ha-1), and wheat-pea (0.71 kg N ha-1) due to an additional N fertilization event. Cumulative losses from unfertilized cropping systems were not different from perennial grass-alfalfa (0.28 kg N ha-1). Tillage did not affect N2O losses for the wheat-fallow systems. Mean FIE level was equivalent to 0.26% of applied N, and considerably below the Intergovernmental Panel on Climate Change mean default value (1.25%).
  • Authors:
    • Lal, R.
    • Elder, J. W.
  • Source: Soil & Tillage Research
  • Volume: 98
  • Issue: 1
  • Year: 2008
  • Summary: As in other drained, intensively cultivated Histosols of the world, soil subsidence is a growing concern of vegetable farmers in the muck crops region of North Central, Ohio. Subsidence in organic soils is caused primarily by aerobic degradation of soil organic matter (SOM), which in turn makes available large quantities of once bound C and N. Upon drainage and cultivation, soil C and N dynamics shift drastically. Organic soils transition from CO2 and organic N sinks, to persistent sources, whereas CH4 uptake capacity increases. Therefore, this study was conducted to assess the short-term (within the first year) impact of conversion of intensively tilled organic soils to no-till management. The specific objectives of this study were to: (i) compare soil moisture content, soil temperature, and greenhouse gas (GHG) emission rates from moldboard/disking (MB), no-till (NT), and bare (B) treatments in cultivated organic soils, and (ii) estimate the rate of subsidence associated with these tillage practices. Over the year, soil moisture content (SMC) was significantly higher in MB (0.90 kg kg-1) than B (0.84 kg kg-1) treatments; however NT (0.87 kg kg-1) was not significantly different from either MB or B treatments. Mean annual temperatures at 5 cm depth were significantly higher in B (16.9 °C) compared to MB (16.2 °C) and NT (15.9 °C) treatments The CO2 emissions were not significantly different among treatments, while N2O emissions were significantly higher from MB (96.9 kg N2O-N ha-1 yr-1) than NT (35.8 kg N2O-N ha-1 yr-1) plots. Both CH4 uptake and CH4 emission exhibited low annual flux in all treatments.