Effect of Inorganic Fertilizer Application on Green House Gas Emissions
and Microbial Activity under Coffee Agroforestry in Eastern Uganda
Abstract
A study was conducted in none tilled coffee agroforestry fields of
Eastern Uganda to understand the effects of application of inorganic
fertilizers on soil nutrient loss in form of gas for mitigation of
unsustainable agricultural practices. This study specifically i)
assessed the effect of application of inorganic fertilizers on
greenhouse gas emissions, ii) determined their effect on microbial
carbon, nitrogen and phosphorus and iii) determined their effect on leaf
litter decomposition under Albizzia-coffee growing systems of the Mount
Elgon. Soil gas emissions were measured with the static chamber method
for twelve months in a field experiment with five different fertilizer
treatments. The effect of treatments was separated using ANOVA in
Genstat discovery version 13. Microbial carbon, nitrogen and phosphorus
was separated using Mann-Whitney U test. Results showed that annual
emissions ranged from 19.6 to 26.1 (t C/ha/yr), 3.5 to 9 (Kg N/ha/yr)
and 6.9 to 9.2 (Kg C/ha/yr) for carbon dioxide, nitrous oxide and
methane respectively. Significant effects on soil emissions only
occurred for nitrous oxide (P=0.017), microbial carbon (p=0.001) and
microbial phosphorus (p<0.001) for the study period. The
mixture of NPK fertilizers presented the lowest carbon dioxide loss and
application of TSP presented the lowest nitrous oxide emission from
soil. This study underscores the need for establishment of long-term
experiments across several agro-ecological zones to confirm farmers’
perceptions of their soil fertility levels and ascertain the
contribution of farm practices towards the retention of nutrients in the
soil with minimal emission, to inform decisions of small holder farmers,
policy and development partners for sustainable production.