Distribution of nitrate and related nutrient stocks in a fertilised horticultural valley soil in central Uganda

Abstract

The drive to modernise agriculture in Uganda is generally resulting in increased utilisation of
agrochemicals, including fertilisers. Unregulated use of many chemicals is widely believed
to be a threat to agroecologies and, consequently, to human livelihoods. Unfortunately, use of
agrochemicals is inevitable especially in light of the increasingly dwindling natural resource
base, and the ensuing plant physiological stresses. A study was conducted at the Makerere
University Agricultural Research Institute, Kabanyolo in central Uganda, to evaluate a
horticultural soil for the distribution of nitrate ion species and other important soil properties
within soil profiles, relative to the water table. Soil samples were taken from four representative
sub-sites (as replicates) within a valley, at depths of 0-20, 20-40, 40-60, 60-80 and 80-100 cm.
The entire profile depth was strongly acidic, with pH values <4.5. Vertical nitrate movement
within the profile was phenomenal and caused a bulge in the lower depths of the soil profile.
Soil organic matter and total N followed suit, suggesting a reasonable intensity of drainage
within this valley soil. The water table was as high as 80 cm profile level, hence, the potential
for nitrate loading into groundwater is high.