Improved analysis of organic manures
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Demonstration plots on manure nutrient value
Fertiliser inputs represent the biggest single cost component of cereal crop production, e.g. representing >60% of the variable costs of winter wheat. Manures can make a major contribution towards crop nutrient requirements and these plots set out to demonstrate how manures can be used as a reliable source of nitrogen (N), phosphate and potash.
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The aim of the project is to substantially extend the sustainable recycling of organic manures and residues in UK agriculture, through the development of NIRS as a robust and reliable technology for multi-nutrient analysis. The project also aims to develop an innovative NIRS-based predictive capacity for estimating the rate and extent of nitrogen (N) release arising from the organic-N content of manures. These developments will reduce the environmental impacts of manure use and increase profitability in crop production.
During 2009, a total of 1154 samples were collected and scanned, with the considerable support of project partners. The total comprised 254 pig FYM, 135 pig slurry, 373 cattle FYM, 145 cattle slurry and 247 biosolids samples. Samples have been multi-scanned (6x) and analysed (Fig 2a and 2b). Following completion of this work, further refinement of the calibration models will be undertaken. It is anticipated that the final calibration models will be based on more than 400 conventionally analysed samples, significantly beyond the originally projected number of 250. During the past year it has become apparent that a large number of low dry matter samples, with very low solids content (dirty water samples) and very low nutrient content (at ppm level), compromise the reliability of the model and should be excluded from the calibration; such samples are almost translucent and unsuitable for reflectance-based analysis.
Figure 1: Preliminary NIRS calibration model for manure dry matter content.
Figure 2: Development of NIRS calibration models.
Homogenisation of samples of solid manures (a) following quick freezing in liquid nitrogen (b).
a. 
b. 
Ryegrass in pots has been used to track the release of N from manures, as described in last year’s annual report (page 85), with 30 selected manures applied to three different soil types at ADAS Boxworth and North Wyke (60 manures in total). Dry matter yield and N offtake were recorded from five cuts of grass. Nitrogen release from the manures has been similar to that observed in year one, with greatest recovery in the first cut from slurries, elevated N offtake from FYM extended to second and third cuts and a more even N release observed across the cuts from conditioned biosolids. Results from the N release studies, across a total of 180 manures over the three years, will provide a basis for developing an NIRS model for the prediction of the longer term N release characteristics of manures.
In contrast to the development of NIRS for manure analysis, application of the technique to provide information on nutrient content in soils has, so far, proved of limited success; from the wide range of soils used in the project, NIRS has given poor statistical validation and it appears likely to provide more consistent results when used on the same, or closely related, soil types, which would present a severe limitation on it’s potential. In the final year of the project, the research will assess the potential of NIRS for estimation of phospholipid fatty acid (PLFA) content of soils, as an indicator of soil biological activity, ie its potential for being a soil ‘health check’.
Industry interest in the research has remained high and information was presented via a number of activities during 2009, including Cereals Event (demonstration plots), Dairy Event (Muck clinic), articles in Crops magazine and FWi, HGCA workshops and the HGCA national Agronomy Conference.
For more information about this project contact Dr Lizzie Sagoo, ADAS Boxworth (Tel: 01954 267666; e-mail: Lizzie.Sagoo@adas.co.uk).
Page last updated 08 June 2010