• Authors:
    • Torbert, H. A.
    • Scopel, E.
    • Velazquez-Garcia, I.
    • Potter, K. N.
  • Source: Journal of Soil and Water Conservation
  • Volume: 62
  • Issue: 2
  • Year: 2007
  • Summary: While no-till management practices usually result in increased soil organic carbon (SOC) contents, the effect of residue removal with no-till is not well understood, especially in warmer climates. A multi-year study was conducted at six locations having a wide range of climatic conditions in central Mexico to determine the effect of varying rates of residue removal with no-till oil SOC. Mean annual temperatures ranged from 16 degrees C to 27 degrees C (61 degrees F to 81 degrees F). Mean annual rainfall ranged from 618 to 1099 min yr(-1) (24 to 43 in yr(-1)). Treatments consisted of annual moldboard plowing under residue and no-till with 100%, 66%, 33%, and no corn (Zea mays L.) residue retained oil the no-till surface. At five of the six locations, no-till with all surface residues removed maintained SOC levels above that of moldboard plowing which incorporated all residues. Retaining 100% of the crop residues with no-till always increased or maintained the SOC content. SOC increased in cooler climates, but as mean annual temperature increased, more retained crop residues were needed to increase the SOC. In tropical (mean annual temperature > 20 degrees C) conditions, 100% corn residue retention with no-till only maintained SOC levels. Mean annual temperature ad a greater impact oil SOC than did annual rainfall. It appears that, in warmer climates, residue in excess of that needed for erosion control may be used for animal fodder or energy production. At the higher temperatures, most of the residue will decompose if left oil the soil surface Without improving soil carbon contents.
  • Authors:
    • Valentini, R.
    • Tubaf, Z.
    • Sutton, M.
    • Manca, G.
    • Stefani, P.
    • Skiba, U.
    • Rees, R. M.
    • Baronti, S.
    • Raschi, A.
    • Neftel, A.
    • Nagy, Z.
    • Martin, C.
    • Kasper, G.
    • Jones, M.
    • Horvath, L.
    • Hensen, A.
    • Fuhrer, J.
    • Flechard, C.
    • Domingues, R.
    • Czobel, S.
    • Clifton-Brown, J.
    • Ceschia, E.
    • Campbell, C.
    • Amman, C.
    • Ambus, P.
    • Pilegaard, K.
    • Allard, V.
    • Soussana, J. F.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 121
  • Issue: 1-2
  • Year: 2007
  • Summary: The full greenhouse gas balance of nine contrasted grassland sites covering a major climatic gradient over Europe was measured during two complete years. The sites include a wide range of management regimes (rotational grazing, continuous grazing and mowing), the three main types of managed grasslands across Europe (sown, intensive permanent and semi-natural grassland) and contrasted nitrogen fertilizer supplies. At all sites, the net ecosystem exchange (NEE) of CO2 was assessed using the eddy covariance technique. N2O emissions were monitored using various techniques (GC-cuvette systems, automated chambers and tunable diode laser) and CH4 emissions resulting from enteric fermentation of the grazing cattle were measured in situ at four sites using the SF6 tracer method. Averaged over the two measurement years, net ecosystem exchange (NEE) results show that the nine grassland plots displayed a net sink for atmospheric CO2 of -240 +/- 70 g C m(-2) year(-1) (mean confidence interval at p > 0.95). Because of organic C exports (from cut and removed herbage) being usually greater than C imports (from manure spreading), the average C storage (net biome productivity, NBP) in the grassland plots was estimated at -104 +/- 73 g cm(-2) year(-1) that is 43% of the atmospheric CO2 sink. On average of the 2 years, the grassland plots displayed annual N2O and CH4 (from enteric fermentation by grazing cattle) emissions, in CO2-C equivalents, of 14 +/- 4.7 and 32 +/- 6.8 g CO2-C equiv. m(-2) year(-1), respectively. Hence, when expressed in CO2-C equivalents, emissions of N2O and CH4 resulted in a 19% offset of the NEE sink activity. An attributed GHG balance has been calculated by subtracting from the NBP: (i) N2O and CH4 emissions occurring within the grassland plot and (ii) off-site emissions of CO2 and CH4 as a result of the digestion and enteric fermentation by cattle of the cut herbage. On average of the nine sites, the attributed GHG balance was not significantly different from zero (-85 +/- 77 g CO2-C equiv. m(-2) year(-1)).
  • Authors:
    • Mangum, R. W.
    • Coffman, C. B.
    • Teasdale, J. R.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 5
  • Year: 2007
  • Summary: There have been few comparisons of the performance of no-tillage cropping systems vs. organic farming systems, particularly on erodible, droughty soils where reduced-tillage systems are recommended. In particular, there is skepticism whether organic farming can improve soils as well as conventional no-tillage systems because of the requirement for tillage associated with many organic farming operations. A 9-yr comparison of selected minimum-tillage strategies for grain production of corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.) was conducted on a sloping, droughty site in Beltsville, MD, from 1994 to 2002. Four systems were compared: (i) a standard mid-Atlantic no-tillage system (NT) with recommended herbicide and N inputs, (ii) a cover crop-based no-tillage system (CC) including hairy vetch (Vicia villosa Roth) before corn, and rye (Secale cereale L.) before soybean, with reduced herbicide and N inputs, (iii) a no-tillage crownvetch (Coronilla varia L.) living mulch system (CV) with recommended herbicide and N inputs, and (iv) a chisel-plow based organic system (OR) with cover crops and manure for nutrients and postplanting cultivation for weed control. After 9 yr, competition with corn by weeds in OR and by the crownvetch living mulch in CV was unacceptable, particularly in dry years. On average, corn yields were 28 and 12% lower in OR and CV, respectively, than in the standard NT, whereas corn yields in CC and NT were similar. Despite the use of tillage, soil combustible C and N concentrations were higher at all depth intervals to 30 cm in OR compared with that in all other systems. A uniformity trial was conducted from 2003 to 2005 with corn grown according to the NT system on all plots. Yield of corn grown on plots with a 9-yr history of OR and CV were 18 and 19% higher, respectively, than those with a history of NT whereas there was no difference between corn yield of plots with a history of NT and CC. Three tests of N availability (corn yield loss in subplots with no N applied in 2003-2005, presidedress soil nitrate test, and corn ear leaf N) all confirmed that there was more N available to corn in OR and CV than in NT. These results suggest that OR can provide greater long-term soil benefits than conventional NT, despite the use of tillage in OR. However, these benefits may not be realized because of difficulty controlling weeds in OR.
  • Authors:
    • Dolfing, J.
    • Rappoldt, C.
    • Hol, J. M. G.
    • Mosquera, J.
  • Volume: 2010
  • Year: 2007
  • Summary: Soil compaction stimulates the emission of nitrous oxide (N2O) and methane (CH4) from agricultural soils. N2O and CH4 are potent greenhouse gases, with a global warming potential respectively 296 times and 23 times greater than CO2. Agricultural soils are an important source of N2O. Hence there is much interest in a systematic evaluation of management options that are available to minimize agricultural greenhouse gas emissions, in particular N2O soil emissions. One such option would be to minimize soil compaction due to the use of heavy machinery. Soil compaction in arable land is relatively general. Here we report that emissions of N2O and CH4 from an arable field where soil compaction was minimized through application of the so-called "rijpaden" (riding track) system was substantially lower than from plots where a traditional system was used. Laboratory experiments were used to underpin these observations. From these observations we developed a simple calculation model that relates N2O emission to gas filled pore space and soil respiration as input parameters. We suggest to implement the riding track system on clay rather than sand as farmers benefit from lower compaction in terms of lower risk of compaction and better accessibility of fields for work. The potential reduction of the N2O emission from arable farming in the Netherlands is estimated at ~169 ton N2O-N per year (~0.1 Mton CO2-equivalent). This calculation is based on several assumptions and would benefit from testing assumptions and monitoring effects in agricultural day to day practice.
  • Authors:
    • DEFRA
  • Year: 2007
  • Authors:
    • Sherlock, R. R.
    • Cameron, K. C.
    • Di, H. J.
  • Source: Soil Use and Management
  • Volume: 23
  • Issue: 1
  • Year: 2007
  • Summary: Nitrous oxide (N2O) is a potent greenhouse gas and, in New Zealand, about one-third of the total greenhouse gas emissions from the agricultural sector are of N2O, mostly derived from animal excreta in grazed pasture soils. The aim of this study was to determine the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in reducing N2O emissions from animal urine patches in four different soils located in different regions of New Zealand with different soil, climatic and management conditions. The four soils are Templeton fine sandy loam and Lismore stony silt loam in Canterbury in the South Island, Horotiu silt loam in the Waikato region and Taupo pumice sand near Lake Taupo, both in the North Island. Results showed that the application of a fine-particle suspension nitrification inhibitor, DCD, to grazed pasture soils was very effective in reducing N2O emissions in all four different soils. Total N2O emissions (over 69-137 days) from animal urine patches ranged from 1 to 20.9 kg N2O-N ha-1 without DCD. These were reduced to 0.31-5.7 kg N2O-N ha-1 by the use of DCD, representing 61-73% reductions (with an average of 70% reduction). The N2O-N emission factor from animal urine N, EF3, was reduced from an average of 0.9 to 0.3% by the use of DCD. These results demonstrate the potential of using nitrification inhibitors to mitigate N2O emissions in a wide range of grazed pasture soils under different climatic and management conditions.
  • Authors:
    • Gamroth, M.
    • Hart, J.
    • Sullivan, D.
    • Downing, T.
  • Source: Nutrient Management for Dairy Production
  • Year: 2007
  • Authors:
    • Monaco, S.
    • Sacco, D.
    • Zavattaro, L.
    • Grignani, C.
  • Source: European Journal of Agronomy
  • Volume: 26
  • Issue: 4
  • Year: 2007
  • Summary: Nitrogen (N) and carbon (C) surplus can be used as indicators of an agroecosystems' ability to maintain soil fertility. Maize is the key crop of intensive forage systems in northern Italy, and large amounts of manure are often supplied to this crop. Different maize-based cropping systems and manure managements were compared in this paper. The following were assessed, using the results of an 11-year experiment: crop production and N uptakes; C and N surpluses; soil C and N contents. The treatments were maize for silage (Ms), maize for grain (Mg), double annual crop rotation maize-Italian ryegrass (Mr), and rotation maize-grass ley (Ml). Five fertilization management systems were adopted: 0N control, and bovine slurry and farmyard manure supplied at two levels, ranging from 215 to 385 kg ha-1 of total N. The dry-matter production of Mr was significantly higher than those of the other systems. The response of maize to fertilization was similar in all the cropping systems, except for Mr, for which the crop showed a high reactivity to N input at both fertilizer levels. Soil reserves were rapidly consumed in the unfertilized treatment of Mr, whereas the high productivity potential of this cropping system was exerted in fertilized plots. The introduction of a ley in rotation with maize reduced the system's DM production, due to the low yield potential of grass compared to that of maize, reduced the system response to fertilization, and diminished the exploitation of organic N at high fertilization rates. Cumulated N surplus caused an enrichment of the soil N pool size: 43% of excess N was retained by the soil. The relationship between the cumulated C surplus and the soil C pool size indicated that 26-27% was retained by the soil. Crop residues of the Mg system were less effective in building up the soil C pool than other C sources. Both slurry and farmyard manure exerted a positive effect on the soil C and N retention. When farmyard manure was used, 18% of C and 45% of surplus N were incorporated into the soil organic matter (SOM). Slurry also built up the SOM content, resulting in 9% of C and 24% of N surplus.
  • Authors:
    • Wright, J.
    • Herrick, J.
    • Fredrickson, E.
    • Bestelmeyer, B.
    • Brown, J.
    • Skaggs, R.
    • Peters, D. P. C.
    • Havstad, K. M.
  • Source: Ecological Economics
  • Volume: 64
  • Issue: 2
  • Year: 2007
  • Summary: The over 300 million ha of public and private rangelands in the United States are characterized by low and variable precipitation, nutrient-poor soils, and high spatial and temporal variability in plant production. This land type has provided a variety of goods and services, with the provisioning of food and fiber dominating through much of the 20th century. More recently, food production from a rangeland-based livestock industry is often pressured for a variety of reasons, including poor economic returns, increased regulations, an aging rural population, and increasingly diverse interests of land owners. A shift to other provisioning, regulating, cultural, and supporting services is occurring with important implications for carbon sequestration, biodiversity, and conservation incentives. There are numerous goods and services possible from rangelands that can supply societal demands such as clean water and a safe food supply. The use of ecologically-based principles of land management remains at the core of the ability of private land owners and public land managers to provide these existing and emerging services. We suggest that expectations need to be based on a thorough understanding of the diverse potentials of these lands and their inherent limits. A critical provisioning service to rangelands will be management practices that either maintain ecological functions or that restore functions to systems that have been substantially degraded over past decades. With proper incentives and economic benefits, rangelands, in the U.S. or globally, can be expected to provide these historical and more unique goods and services in a sustainable fashion, albeit in different proportions than in the past.
  • Authors:
    • Tourdonnet, S. D.
    • Carof, M.
    • Coquet, Y.
    • Hallaire, V.
    • Roger-Estrade, J.
  • Source: Soil Use and Management
  • Volume: 23
  • Issue: 3
  • Year: 2007
  • Summary: We studied soil hydraulic conductivity (K) and porosity in five combinations of soil tillage and cover crop management systems. Treatments were winter wheat (Triticum aestivum L.) grown on a conventionally tilled soil (CT), on a no-till soil (NT), and on an NT with three different cover crops: red fescue (Festuca rubra L.; Fr), bird's-foot-trefoil (Lotus corniculatus L.; Lc) and alfalfa (Medicago sativa L.; Ms). Measurements were made on a loamy soil in Grignon, France, in November 2004, May 2005 and October 2005. K and mean size of hydraulically active pores were measured in situ at three water potentials (22120.6, 22120.2 and 22120.05 kPa) at the soil surface and at 10 cm depth. In November 2004 and May 2005, pore space was described using 2D image analysis of pores on undisturbed soil samples in the 0201310 cm layer and in the 10201320 cm layer. The major differences were caused by soil tillage that created two heterogeneous soil layers and increased K in the 0201310 cm layer relative to NT. The effects of cover crop on K and porosity were not affected by the root type: there were no major differences between the grass cover crop (fibrous-root type) and the leguminous ones (tap-root type). However, we recorded larger functional pores and more tubules in the no-till treatments with a cover crop, compared with the no-till treatment without cover crop; this was probably the result of root activity. Although these changes generally did not result in larger values of K, they participated in the maintenance of soil structure and K over time.