Assessment of the nitrogen and phosporous fertiliser value of ruminant manure in Mpumalanga Province South Africa
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Abstract
To improve understanding of the diversity in the nitrogen and phosphorus content and release properties of free-ranging ruminant manure found on smallholdings in Mpumalanga Province, 30 manure samples were collected from livestock enclosures located in three different vegetation units (viz, Central Sandy Bushveld, Ka Ngwane Montane Grassland and Granite Lowveld) representing contrasting levels of palatability of their grass components. Interviews with owners of ruminant livestock and animal enclosures provided information on factors that could have affected the composition of the manure in their livestock enclosures. Chemical analysis revealed the N content of cattle and goat manure (mean of 1.86% and 2.38%, respectively). First-season release in plant-available forms of the N and P contained in these samples was determined using incubation and a pot-based method. Whilst these methods provided different estimates of the nitrogen fertiliser value of manure, both showed that goat manure released a greater proportion of the N it contained in plant-available forms (15.7% and 33.7%) than cattle manure (9.6% and 20.8%). Diets richer in N and the complete or partial roofing of goat enclosures were identified as the two most likely factors that caused goat manure to be superior to cattle manure as an N fertiliser. On average, goat manure had a higher P content (0.36%) than cattle manure (0.24%). Release of P contained in goat manure was also slightly higher than that of P contained in cattle manure. Using the pot-based method, goat manure released 87.0% of P and cattle manure 80.6%, on average. The incubation method yielded somewhat lower release values, namely 82.5% for goat manure and 77.0 for cattle manure, on average. Based on the incubation results, the first-season N-fertiliser value of cattle manure was 2.83 g N kg dry manure-1 and 5.84 g N kg dry manure-1 for goat manure. The first-season P-fertiliser value of cattle manure was 1.89 g P kg dry manure-1 and 3.05 g P kg dry manure-1 for goat manure. Overall, the study confirmed the value of ruminant manure for use as a fertiliser in crop production.
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Submitted in partial fulfilment of the requirements of the degree Magister Technologiae Agriculture in the Department of Crop Sciences, Faculty of Science at the Tshwane University of Technology
Date
2021-12
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Tshwane University of Technology
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Keywords
Nitrogen, Phosporous fertiliser, Ruminant manure, Mpumalanga, South Africa