Land evaluation for crop production in Upper Kabete Campus field, University of Nairobi, Kenya

Abstract

Background The study area exhibits a first class catena; variation in soils is a result of differences in drainage and lateral movement of materials. The site was delineated into Soil Mapping Units (SMUs) through augering, into soils differing in macro relief. Slope categories included 0 to 5%, 5 to 8%, 8 to 16%, 16 to 30% and > 30%. Profile pits were opened in the five mapping units using stratified random sampling technique. Identified SMUs include UmIr/F, UmIr/E, UxIr/D, UxIr/C and UxIr/AB in order of decreasing slope gradient. Land suitability classification was based on the top horizons and the FAO 1976 criterion for land evaluation was used. The study aimed at identifying the most suitable areas for envisaging production of common crops grown in the area and limitations to production increase. A table of relevant land qualities and their diagnostic factors was constructed, rated and matched with suitability class-defining criteria to determine current suitability. Potential suitability was determined by considering the possibility of resolving the current limitations.

Results Mapping unit UmIr/F and UmIr/E qualified as class S2 for the selected crops majorly due to limitations of workability and susceptibility to erosion based on their slope gradient. Nutrient availability and possibility of use of implements also rated as S2. Unit UxIr/D qualified in S2 category due to the same limitations. Mapping unit UxIr/C and UxIr/AB qualified in the S2 category due to limitations of nutrient availability. After improvements, all the mapping units qualified in class S1.

Conclusions These observations indicate that workability and erosion susceptibility due to steep topography coupled with lack of enough nutrients are the greatest production limitations in the study area. Increasing slope gradient also led to decreasing possibility of use of farm implements. Terracing can reduce the deleterious influence of slope on soil quality, shifting suitability to a higher class, should the steep area be used for cultivation. There is a need for sufficient inputs and cover cropping to maintain high soil quality. Land evaluation should be part of good agricultural practices in any production system.