3 results
Impact of reduced tillage on soil organic carbon and nutrient budgets under organic farming
- Florian Gadermaier, Alfred Berner, Andreas Fließbach, Jürgen Kurt Friedel, Paul Mäder
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- Journal:
- Renewable Agriculture and Food Systems / Volume 27 / Issue 1 / March 2012
- Published online by Cambridge University Press:
- 12 January 2011, pp. 68-80
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No-tillage (NT) and reduced tillage (RT) systems are well-known management tools for reducing soil erosion and improving soil fertility. NT and RT may improve the environmental and economic performance of organic farming, but they are still not common practice among organic farmers. This paper presents the effects of tillage [RT versus conventional tillage (CT)], fertilization (slurry versus manure compost) and biodynamic preparations (with versus without) on soil fertility indicators such as soil organic carbon (Corg), microbial biomass and microbial activity, soil nutrients and nutrient budgets in an organic farming system during the first six-year crop rotation period of a long-term experiment on a clayey soil in a temperate climate. RT caused stratification of soil organic carbon (Corg), microbial properties and soil nutrients in the soil profile. Under RT, Corg in the 0–10 cm soil layer increased from 2.19 to 2.61% (w/w) from 2002 to 2008, whereas it remained constant under CT. In both tillage treatments, Corg remained constant in the 10–20 cm soil depth. Microbial biomass C increased by 37% under RT in the 0–10 cm soil depth and microbial activity [dehydrogenase activity (DHA)] was enhanced by 57%. Soil microbial biomass C and DHA in the 10–20 cm soil depth were also higher under RT (+10 and +17%, respectively). Soluble soil P and K were 72 and 40%, respectively, higher in 0–10 cm soil depth under RT when compared with CT. Fertilization showed no effects on the measured soil properties. Biodynamic preparations increased solely the Cmic-to-Nmic (soil microbial biomass C to soil microbial biomass N) ratio by 7% in the 0–10 cm soil depth. Nutrient budgets for P were balanced in all treatments, but N and K exports were higher under RT compared to CT. We conclude that RT is a suitable method for increasing indicators of soil fertility in organic farming systems. The combined effects of RT and an organic farming system with a diverse, ley-based crop rotation and organic fertilization merit further promotion and it may be considered for supporting actions by the agricultural policy schemes.
Chemistry of bulk precipitation in southwestern Viti Levu, Fiji
- M. J. Waterloo, J. Schelleken, L. A. Bruijnzeel, H. F. Vugts, P. N. Assenberg, T. T. Rawaqa
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- Journal:
- Journal of Tropical Ecology / Volume 13 / Issue 3 / May 1997
- Published online by Cambridge University Press:
- 10 July 2009, pp. 427-447
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The amounts and chemical composition of bulk precipitation were investigated over a continuous 21-mo period (January 1990 to September 1991) at four sites along an East-West transect perpendicular to the coast of Southwest Viti Levu, Fiji. Measured rainfall totals in 1990 ranged from 1796 mm at the coastal Korokula station to 2113 mm at the inland Tulasewa station, which is somewhat higher than the long-term average of 1707 mm at a reference weather station located in the centre of the study area. The first 9 mo of 1991 were relatively dry (range 1027–1533 mm) with a total of 1157 mm at the reference site as compared to a long-term average of 1330 mm. Concentrations of all investigated constituents in bulk rainfall were low, except during the passage of cyclone Sina due to the deposition of large amounts of, especially, chloride, sodium and sulphate in sea spray. Concentrations of sodium and magnesium could be explained fully by maritime contributions to the rainfall composition at all sites. Maritime contributions to the concentrations of calcium, sulphate and potassium accounted for 10–40% of the total, whereas bicarbonate, ammonium, nitrate, silicon, aluminium, iron and manganese were derived exclusively from terrestrial sources. The annual atmospheric nutrient deposition rates were low by pan-tropical standards, particularly when the contribution of cyclone Sina was excluded. Annual totals (in kg ha−1) ranged from 2.4–8.8 for nitrogen, 0.4–1.1 for phosphorus, 2.3–4.9 for potassium, 1.4–1.9 for calcium and from 1.1–1.3 for magnesium. The inclusion of the contribution by the cyclone more than doubled the deposition of potassium, calcium and magnesium, although values still remained well within the range reported for humid tropical areas. The estimated atmospheric deposition of nutrients over a typical rotation period (16 y) was sufficient to balance losses in harvested Pinus caribaea logs (stemwood plus bark) of potassium, calcium and magnesium, but not of nitrogen and, probably, phosphorus. Nutrient losses associated with the harvesting of stemwood alone were compensated entirely by the atmospheric inputs.
Farm-gate nutrient balance assessment of organic dairy farms at different intensity levels in Germany
- G. Haas, C. Deittert, U. Köpke
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- Journal:
- Renewable Agriculture and Food Systems / Volume 22 / Issue 3 / September 2007
- Published online by Cambridge University Press:
- 08 August 2007, pp. 223-232
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Organic farms are characterized as low external input agro-ecosystems. Currently, some organic dairy farmers feed higher amounts of concentrates and succulent feed, some of which is purchased, to increase the dairy performance of their cows. To assess the environmental impact of this practice, nutrient balances at the farm-gate level of 26 organic dairy farms located in two different regions in Germany were compiled and analysed. The farms are characterized by different production features and feeding intensity levels [0–2.72 t dry matter (DM) of concentrates per cow and year, which was 0–378 g kg−1 milk] yielding 5150–8790 kg milk on average per cow and year. The area- and product (milk)-related farm-gate nutrient budgets for P and K are almost balanced [mean −3 kg P ha−1, range (R): −14 to 4 kg P ha−1; −0.5 g P kg−1 milk, R: −2.8 to 0.9 g P kg−1 milk and 1 kg K ha−1, R: −13 to 15 kg K ha−1; 0.1 g K kg−1 milk, R: −2.4 to 3.9 g K kg−1 milk]. The N surplus averages only 43 kg ha−1 (R: 8–85 kg N ha−1) and 8.2 g kg−1 milk (R: 2.1–17.1 g kg−1 milk), but the correlation between the amount of feed purchased on a net basis and N surplus is significant (r=0.56, P=0.003). Average area-related nutrient use efficiency for all farms calculated as the proportion of input to output is high for N (45%), P (164%) and K (91%). The share of nutrient input and output components and correlations between parameters are presented. To classify the results, investigations comparing organic and conventional dairy farming in Europe are listed, indicating an N surplus for organic farms, which is often only half or a third of the surplus of conventional farms. However, intensification in organic dairy farming has, in some cases, significant impacts that need to be assessed to determine its environmental performance and profile.