• Authors:
    • Frede, H. G.
    • Keller, T.
    • Huisman, J. A.
    • Breuer, L.
  • Source: Geoderma
  • Volume: 133
  • Issue: 1-2
  • Year: 2006
  • Summary: Land use change can lead to changes in a range of soil properties, including soil carbon (C) and nitrogen (N) content, bulk density and pH. Previous investigations on the effects of land use change have been biased towards the impact of forest clearing and afforestation in tropical environments. Therefore, the aim of this study is to determine the impact of a conversion from cropland to grassland on soil properties in two districts of the Lahn-Dill Highlands, Germany. We determined a land use history for the period 1945-2004 from aerial photographs and field surveys. This land use history was used to build a chronosequence of grassland sites with a different age since the conversion from cropland for both districts. Each chronosequence was sampled to determine bulk density, pH, coarse material fraction, C/N ratio and soil C and N content as a function of grassland age. Results showed that there was no clear dependency of soil properties on grassland age for both districts. It was concluded that observed differences within each district are much more related to differences in soil parent material or slope position, instead of land use. Interestingly, the reduction of the chronosequence analysis to a paired site survey led to an opposite conclusion for the Erda district because all investigated soil properties were significantly different for continuous grassland and cropland. This indicates that care is required when interpreting results from paired site surveys, especially when the equality of initial soil conditions is not (or cannot be) tested.
  • Authors:
    • Amon, B.
    • Weiland, P.
    • Trimborn, M.
    • Clemens, J.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 112
  • Issue: 2-3
  • Year: 2006
  • Summary: Biogas treatment of animal manures is an upcoming technology because it is a way of producing renewable energy (biogas). However, little is known about effects of this management strategy on greenhouse gas (GHG) emissions during fermentation, storage, and field application of the substrates compared to untreated slurries. In this study, we compared cattle slurry and cattle slurry with potato starch as additive during the process of fermentation, during storage and after field application. The addition of potato starch strongly enhanced CH4 production from 4230 l CH4 m-3 to 8625 l CH4 m-3 in the fermenter at a hydraulic retention time (HRT) of 29 days. Extending the HRT to 56 days had only a small effect on the CH4 production.Methane emissions from stored slurry depended on storage temperature and were highest from unfermented slurry followed by the slurry/starch mixture. Gas emissions from untreated and fermented slurry during storage were further analyzed in a pilot-scale experiment with different levels of covering such as straw cover, a wooden lid and no cover. Emissions of greenhouse gases (CH4,N2O, NH3) were in the range of 14.3-17.1 kg CO2 eq. m-3 during winter (100 day storage period) and 40.5-90.5 kg CO2 eq. m-3 during summer (140 day storage period). A straw cover reduced NH3 losses, but not overall GHG emissions, whereas a solid cover reduced CH4 and NH3 emissions. After field application, there were no significant differences between slurry types in GHG emissions (4.15-8.12 kg CO2 eq. m-3a-1). GHG emissions from slurry stores were more important than emissions after field application. Co-digestion of slurry with additives such as starch has a large potential to substitute fossil energy by biogas. On a biogas plant, slurry stores should be covered gas-tight in order to eliminate GHG emissions and collect CH4 for electricity production.
  • Authors:
    • Nowicki, B. L.
    • Leonard, R.
    • Sherlock, R. R.
    • Bertram, J. E.
    • Clough, T. J.
  • Source: Global Change Biology
  • Volume: 12
  • Issue: 2
  • Year: 2006
  • Summary: There is considerable uncertainty in the estimates of indirect N2O emissions as defined by the intergovernmental panel on climate change's (IPCC) methodology. Direct measurements of N2O yields and fluxes in aquatic river environments are sparse and more data are required to determine the role that rivers play in the global N2O budget. The objectives of this research were to measure the N2O fluxes from a spring-fed river, relate these fluxes to the dissolved N2O concentrations and NO3-N loading of the river, and to try and define the indirect emission factor (EF5-r) for the river. Gas bubble ebullition was observed at the river source with bubbles containing 7.9 lLN2OL-1. River NO3-N and dissolved N2O concentrations ranged from 2.5 to 5.3mg L-1 and 0.4 to 1.9 lgN2O-NL-1, respectively, with N2O saturation reaching 404%. Floating headspace chambers were used to sample N2O fluxes. N2O-N fluxes were significantly related to dissolved N2O-N concentrations (r2 = 530.6) but not to NO3-N concentrations. The N2O-N fluxes ranged from 38-501 microg m-2 h-1 , averaging 171 lgm-2 h-1( SD 85) overall. The measured N2O-N fluxes equated to an EF5-r of only 6.6% of that calculated using the IPCC methodology, and this itself was considered to be an overestimate because of the degassing of antecedent dissolved N2O present in the groundwater that fed the river.
  • Authors:
    • Horfarter, R.
    • Hougaard, H.
    • Broge, N.
    • Knudsen, L.
    • Hansen, O. M.
    • Schelde, K.
    • Thomsen, A.
    • Berntsen, J.
  • Source: Precision Agriculture
  • Volume: 7
  • Year: 2006
  • Summary: Several methods were developed for the redistribution of nitrogen (N) fertilizer within fields with winter wheat (Triticum aestivum L.) based on plant and soil sensors, and topographical information. The methods were based on data from nine field experiments in nine different fields for a 3-year period. Each field was divided into 80 or more subplots fertilized with 60, 120, 180 or 240 kg N ha-1. The relationships between plot yield, N application rate, sensor measurements and the interaction between N application and sensor measurements were investigated. Based on the established relations, several sensor-based methods for within-field redistribution of N were developed. It was shown that plant sensors predicted yield at harvest better than soil sensors and topographical indices. The methods based on plant sensors showed that N fertilizer should be moved from areas with low and high sensor measurements to areas with medium values.The theoretical increase in yield and N uptake, and the reduced variation in grain protein content resulting from the application of the above methods were estimated. However, the estimated increases in crop yield, N-uptake and reduced variation in grain protein content were small.
  • Authors:
    • Andrioli, I.
    • Pereira, M.
    • Fabian, A.
    • Torres, J.
  • Source: Revista Brasileira de Agrociencia
  • Volume: 12
  • Issue: 1
  • Year: 2006
  • Summary: To evaluate the influence of vegetation coverings on soil temperature and humidity, in a medium texture red distrophic latossol, a study was conducted at CEFET-Uberaba, Minas Gerais, Brazil from January to June 2000. A ramdomized complete split plot block design, with 3 replications was used. Eight vegetation covers were allocated to plots: pearl millet ( Pennisetum americanum [ P. glaucum] sin. tiphoides), braquiaria ( Brachiaria brizantha [ Urochloa brizantha]), sorghum ( Sorghum bicolor), pigeon pea ( Cajanus cajan), sun hemp ( Crotalaria juncea) and black oat ( Avena strigosa [ A. nuda]), fallow land and area under conventional system (control). In subplots, maize and soyabean were planted, after vegetation cover desiccation. No significant differences were found among vegetation coverings in relation to soil hydric regime but differences among months were observed. Effect of vegetation cover on soil temperature was shown effectively during the months of May and June, in terms of residues of cultivated crops, mainly maize. Higher values in thermal amplitude were detected under soyabean cropping. Temperatures were higher at 5 cm depth than at 10 cm, in afternoons, under maize and soyabean cultivation.
  • Authors:
    • Di, H. J.
    • Stewart, A.
    • Condron, L. M.
    • Stark, C.
    • O'Callaghan, M.
  • Source: New Zealand Journal of Crop and Horticultural Science
  • Volume: 34
  • Issue: 3
  • Year: 2006
  • Summary: Farming practices can have significant effects on important soil processes, including nitrogen (N) dynamics and nitrate leaching. A lysimeter experiment was conducted to determine differences in N leaching resulting from past and current crop management practices. Intact monolith lysimeters (50cm diam. x 70cm deep) were taken from sites of the same soil type that had either been under long-term organic or conventional crop management. These were then managed according to established organic and conventional practices over 2% years using the same crop rotation (barley (Hordeum vulgare L.), maize (Zea mays L.), rape (Brassica napus L. ssp. oleifera) plus a lupin green manure (Lupinus angustifolius L.)) and two fertiliser regimes, resulting in four treatments based on soil management history and current fertilisation strategy. Dry matter yield of each crop was determined after harvest and leachates were collected after significant rainfall events and analysed for total mineral N concentrations. Mineral fertilisation had a clear positive effect on yields of the first crop, whereas there were no considerable differences between treatments for the last crop owing to a significant positive effect of green manure incorporation on yields. Although there was a trend of lower mineral N leaching from organically fertilised soils (organic management: 24.2 kg N ha(-1); conventional management: 28.6), differences in N losses were not statistically significant between treatments. This shows that under the experimental conditions, leaching losses and crop yields were more strongly influenced by crop rotation and green manuring than by the presence or absence of mineral fertilisation. Overall, the study highlights the benefits of including a green manure in the crop rotation of any farming system.
  • Authors:
    • Kenny, S. N.
    • O'Brien, G. B.
    • Ward, G. N.
    • Jacobs, J. L.
    • Chapman, D. F.
    • Beca, D.
    • McKenzie, F. R.
  • Source: Proceedings of the New Zealand Grassland Association
  • Volume: 68
  • Year: 2006
  • Summary: Continued improvements in home grown forage consumption are needed to support the long-term profitability of the dairy industry in southern Australia. Most home grown forage currently comes from perennial ryegrass pastures, which have significant limitations in the southern Australia environment. These limitations threaten future productivity gains, and we therefore consider opportunities for using other plant species. Data on the production of alternative perennial grasses, brassica summer crops, C4 summer crops and winter cereals grown for whole-crop silage are limited and generally show large variation in yields between sites and years. Simulation models suggest that, once the base ryegrass pasture is well-utilised, incorporating complementary forages can return $70-$100/ha extra operating profit for every additional tonne of home grown forage DM consumed per ha. Double cropping (winter cereal or annual ryegrass followed by a summer crop of turnips or maize) and summer-active pastures such as tall fescue show particular promise. Further information is required on how to integrate these forages into whole farm feeding systems to realise the additional profit with manageable business and environmental risk.
  • Authors:
    • Barker-Reid, F.
    • Gates, W. P.
    • Eckard, R. J.
    • Wilson, K.
    • Baigent, R.
    • Galbally, I. E.
    • Meyer, C. P.
    • Weeks, I. A.
  • Source: 4th International Symposium on non-CO2 Greenhouse Gases
  • Year: 2005
  • Authors:
    • R,Leuning
    • IE,Galbally
    • K,Kelly
    • R,Edis
    • Y,Li
    • D,Turner
    • D,Chen
  • Source: 4th International Symposium on non-CO2 Greenhouse Gases
  • Year: 2005
  • Authors:
    • Denmead, O.T.
    • Bryant, G.
    • Reilly, R.
    • Griffith, D. W. T.
    • White, I.
    • Stainlay, W.
    • Melville, M. D.
    • Macdonald, B. C. T.
  • Source: Proceedings of the Australian Society of Sugar Cane Technologists
  • Volume: 27
  • Year: 2005