The effects of climate on decomposition of cattle, sheep and goat manure in Kenyan tropical pastures

Yuhao Zhu,Lutz Merbold,Petri Pellikka,Alice Anyango Onyango,Felix Ngetich,David E Pelster,Sheila Abwanda Okoma,Sonja Leitner,Klaus Butterbach-Bahl

doi:10.1007/s11104-020-04528-x

Abstract

AimsDecomposition of manure deposited onto pasture from grazing animals represents an important process for carbon (C) and nitrogen (N) cycles in grassland systems. However, studies investigating manure decomposition are scarce; especially in sub-Saharan Africa (SSA).MethodsIn this study, we measured decomposition of three types of animal manure (cattle, sheep, goat) over >1 year using litter bags at four climatically different sites across Kenya. Results Manure dry matter, total C, total N and ammonium concentrations decreased exponentially, with the most rapid decrease occurring during the first few weeks following application, followed by slower changes during the following 2–3 months. Rates of N mineralization were lower than those for C mineralization, resulting in decreasing C/N ratios over time. Generally, cattle manure decomposed faster than sheep or goat manure despite having a higher initial C/N ratio and lower N concentration, with decomposition rates for dry matter ranging from 0.200 to 0.989 k year−1. Cellulose decomposed first, while lignin concentrations increased among all manure types and at all sites.ConclusionsWe found that total manure decomposition rates were positively correlated with cumulative precipitation and aridity index, but negatively correlated with mean temperature. Our results show much slower decomposition rates of manures in semi-arid tropical environments of East Africa as compared to the few previous studies in temperate climates.

Highlights

Decomposition is a critical ecosystem function (Wilkinson 2006) that is fundamental to nutrient, carbon (C) and energy cycling within and among ecosystems, and between the biosphere and atmosphere (Schlesinger and Bernhardt 2013; Wieder et al 2013)
We found that total manure decomposition rates were positively correlated with cumulative precipitation and aridity index, but negatively correlated with mean temperature
Our results show much slower decomposition rates of manures in semi-arid tropical environments of East Africa as compared to the few previous studies in temperate climates

Summary

Introduction

Decomposition is a critical ecosystem function (Wilkinson 2006) that is fundamental to nutrient, carbon (C) and energy cycling within and among ecosystems, and between the biosphere and atmosphere (Schlesinger and Bernhardt 2013; Wieder et al 2013). Decomposition largely results from the activities of soil microorganisms and macrofauna, which break down complex non-living organic matter (e.g. protein, cellulose) into smaller oligo- and monomers (e.g. amino acids, sugars) to gain energy and matter to build and maintain their biomass (Handa et al 2014; Bradford et al 2016). This process can be divided into two stages: The early decomposition stage, during which up to 40%. Decomposition in natural ecosystems is synchronized with plant growth, while anthropogenic disturbance may retard or accelerate decomposition rates in managed ecosystems (Banegas et al 2015)

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Conclusion