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Kenyatta University (2019)

Effects of Longterm Application of Organic Residues and Inorganic Fertilisers on Soil Microbial Biomass, Diversity and Activities in Nyabeda, Siaya County, Kenya

Bolo, Peter Omondi

Titre : Effects of Longterm Application of Organic Residues and Inorganic Fertilisers on Soil Microbial Biomass, Diversity and Activities in Nyabeda, Siaya County, Kenya

Auteur : Bolo, Peter Omondi

Université de soutenance  : Kenyatta University

Grade : MASTER OF ENVIRONMENTAL STUDIES IN AGROFORESTRY AND RURAL DEVELOPMENT 2019

Résumé partiel
Food insecurity is a global problem exacerbated by poor agricultural productivity due to poor soil health, soil infertility, and improper agricultural management practices. Conservation agriculture (CA) practices have been widely promoted and adopted in many regions, but little is known concerning their effects on soil health. This study focused on assessing the effect of long term use of mineral fertilizers, organic inputs and lime on soil microbes and their activities under different tillage and cropping systems. The specific objectives of the study were ; (i) to determine the effects of long term use of mineral fertilizers, organic inputs and lime on soil microbial biomass, composition, abundance and enzymatic activities under different tillage and cropping systems ; (ii) to determine how soil microbes influence soil aggregation under different tillage and cropping systems ; (iii) to determine how tillage and cropping systems influence denitrification and net nitrogen mineralization in the soil. The study involved twelve treatments set up in randomized complete block design. Illumina Miseq sequencing was used to identify the microbial species present whose abundances were assessed using both Simpson’s and Shannon Wienner diversity indices. Aggregate stability was assessed using wet sieving technique ; while denitrification potentials was determined using acetylene incubation technique ; and net nitrogen mineralization assessed using In-situ resin core incubation methods. Data was analysed using R Project. Analysis of variance (ANOVA) was done and means separated using Tukey’s HSD test. Practicing reduced tillage significantly increased microbial populations, with Glomerales increasing by 50.3% relative to conventional tillage.

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