Sampling Procedures for Piggery Slurry in Deep Pits for Estimation of Nutrient Content

• Autores: Pius M. Ndegwa, Jun Zhu
• Localización: Biosystems engineering, ISSN 1537-5110, Vol. 85, Nº 2, 2003, págs. 239-248
• Idioma: inglés
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• Resumen

  • Accurate application rates of pig manure during pump out time depend on the correct determination of nutrient contents of the manure, which in turn is a function of the integrities of the samples or the sampling method. This study compared two sampling methods for obtaining representative samples from three different sources of manure prior to the actual pump out time from pig manure stored in pits, to a control method. In addition, empirical relationships between nutrients (nitrogen and phosphorus) and total solids that could help in quicker determinations of the manure nutrient contents on-site during scheduled pump out time were also investigated. Results showed that, stirring representative manure in a 200 l barrel for a period of at least 5 min using a paddle-stirrer such as the one described in this study is adequate for complete homogenisation of manure essential for drawing off a representative sample from any point in the barrel. Further, results showed that, the use of a sump pump (such as the one described in this study) placed at the bottom of a similar barrel and oriented to shoot manure horizontally is also adequate for homogenising the manure after 5 min of operation: a procedure that also allows for collection of a representative sample from any point in the container. Using the above two techniques, correct nutrient determinations are possible before the pumpout date, allowing for proper planning of the manure application in the field. The value for correlation coefficient R of 0·24 for a linear regression between total solids (TS) and total Kjeldahl nitrogen (TKN) using data obtained in this study was low suggesting that the content of TS cannot be used to estimate the TKN content. However, the value for the correlation coefficient R of 0·92 for a linear regression between TS and total phosphorus (TP) obtained using data from this study indicated that, TS can be used to estimate the TP in the manure.