EFFECTS OF FARMING PRACTICES ON THE LEVELS OF TURBIDITY, NITRATES, AND PHOSPHORUS IN RIVER RUPINGAZI IN EMBU WEST SUB COUNTY, KENYA

Abstract

River Rupingazi catchment in Embu West Sub-County of Kenya has recently undergone unchecked rapid
land use change from natural vegetation to urbanization and agriculture with varying farming practices. Effects of land-use changes on water quality in this catchment is not well documented. This river is primary
source of livelihood for about 116,700 inhabitants in the sub county. An ecological survey was carried out to
determine the effect of farming practices on the levels of turbidity, nitrates, and phosphorus in the 24 km
reach of River Rupingazi. A transect walk along was used for dividing the reach into 7 zones. These include
the; Main Tea zone, Tea zone, Tea/Coffee zone, Coffee zone, Mixed Farming zone, Town zone, and Livestock zone. Four major farming practices prevalent across the seven zones are the growing of perennial
crops, perennial cover crops and non-perennial crops, and constructed soil conservation structures. Triplicate
water samples were randomly collected at the entry and exit of each zone and tested for turbidity, nitrates
and phosphorous. One-way ANOVA at P< 0.05 was used for data analysis using Statistical Package for Social Scientists (SPSS) software. There were no statistically significant differences in mean values of turbidity
(P = 0.067), nitrates (P = 0.281) and phosphorus (P= 0.189) in water at the seven study sites. Furthermore, it
was established that main farming practices in the study area influenced the levels of study parameters.
Combination of the soil and water conservation structures and perennial crops in the Main Tea and Coffee
zones resulted to lower levels of turbidity, nitrates, and phosphorus in the study reach. Tea/Coffee zone with
a combination of cover crops and soil and water conservation structures recorded the lowest levels of turbidity, nitrates and phosphorous in the river water. Zones with non-perennial crops had comparatively higher
level of the measured parameters. It is therefore recommended that combination of various land use practices
should be applied to improve the water quality parameters particularly in the riparian buffer strip of upper
regions of rivers where bank have steep gradient.