Measurement and characterisation of nitrogen release from selected types of animal manure.
Fakude, Sithembiso Bethwell
Fakude, Sithembiso Bethwell
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Abstract
The aim of this two-part study was to contribute to improved understanding of the effects of applying animal manure on the plant- availability of N in soil. The objective of the first part was to assess the validity of the apparent relative nitrogen fertiliser (ARNFV) assay, which is a quick, relatively cheap pot-based method that uses the measurement of maize biomass production over a 42-day period to estimate the first-season NFV of organic sources of N added to soil. Comparing the nitrogen fertiliser value (NFV) estimates of nine manure samples obtained with the ARNFV assay with those provided by established methods, it was found that ARNFV assay estimates were closely correlated with net mineral N release from the manure samples during incubation and also with N yield. However, the assay had the flaw of assuming that the N content of the maize plants across treatments was constant. This assumption was shown to be invalid, because the N content of maize plants grown in the control treatment was in most instances lower than that of plants grown in soil amended with manure, which, in turn, was lower than the N content of plants grown in the chemical N treatment. Despite this flaw, the ARNFV assay could be used to good effect to obtain an indication of the first season NFV of organic sources of N. The second part of the study related to the low first-season NFV of the cattle manure samples that featured in the ARNFV assay and its objective was to determine the effect of combining the application manure and chemical N fertiliser on plant-availability of N in soil and on the NFV of a cattle kraal manure sample. The results confirmed that the strategy increased plant-availability of N in soil but quantitatively, this increase was identical to that obtained by applying the chemical source of N without manure addition, implying that the strategy had no effect on the NFV of the manure used.
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Submitted in partial fulfilment of the requirements for the degree, Magister Technologiae: Agriculture in the Department of Crop Sciences, Faculty of Science at the Tshwane University of Technology.
Date
2019-11-02
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Tshwane University of Technology
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Keywords
Animal, Manure, Soil, Nitrogen fertilise, Biomass production