Effect of Poultry Manure on the Leaching of Carbon from a Sandy Soil as a Potential Substrate for Denitrification in the Subsoil
✍ Scribed by Bhogal, Anne; Shepherd, Mark
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 331 KB
- Volume
- 74
- Category
- Article
- ISSN
- 0022-5142
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✦ Synopsis
There is evidence from laboratory incubations that denitrifying bacteria occur in the deep subsoils of UK soils and that lack of available carbon (C) generally limits their activity. Animal manures can be a source of substantial carbon input to farming systems. This experiment measured the e †ect of broiler litter application on the movement of C in soil solution to depths below 1 m, which might be sufficient to allow denitriÐcation of nitrate moving from the rooting zone towards ground water aquifers. Six broiler litter rates were applied each autumn from 1992È1994 to Ðeld plots on a loamy medium sand in Nottinghamshire, UK. Total loadings over the 3 years ranged from 0 to 125 t ha~1 broiler litter, supplying 0È32 t ha~1 total C. TeÑon and ceramic water samplers, placed at 1É0 and 1É5 m, and monolith lysimeters (0É5 m2 area, 1É5 m deep) were used to measure total organic carbon (TOC) concentrations in the drainage. Ceramic samplers indicated signiÐcantly (P \ 0É05) larger concentrations than TeÑon samplers ; there were no di †erences between concentrations measured by TeÑon samplers and the lysimeters. Water samples analysed for both dissolved and total C showed that nearly all was in a dissolved form. TOC concentrations on plots which received no manure were less than 20 mg litre~1 at 1 m for the duration of the experiment ; concentrations peaked at 65 mg litre~1 with the largest manure loading. There was a linear relationship between C leached and C applied, with about 5% leached below 1 m by the end of the experiment. There was some evidence of movement of C to 1É5 m depth, but there were no large peaks corresponding to those at 1 m, because of either adsorption or microbial utilisation. The results provide evidence of movement of substantial C to depth in some circumstances, particularly on Ðelds which regularly receive large dressings of organic manure. The availability of this as a substrate for denitriÐcation needs further examination.