Epsilon Archive for Student Projects

Abstract

To evaluate the effects of long-term application of organic and mineral fertilizers on maize yield and
soil properties and further to investigate differences in soil fertility gradients, the Tropical Soil Biology
and Fertility Institute of the International Centre for Tropical Agriculture (TSBF-CIAT) conducted an 8-
year experiment on 12 farms in the districts Nyalgunga, Nyabeda and Vihiga in the Western Province
of Kenya. The study was designed as a split plot model where each farm was split into high and low
fertility plots on which the following treatments were applied: T2 – no fertilizer application (control),
T4 – application of farmyard manure (FYM) alone and T5 – combined application of FYM, Mavuno
fertilizer and top dressing. In scope of this thesis the physical soil properties such as bulk density
(BD), soil texture , infiltration rate (IF) and aggregate stability (AS) as well as the soil organic carbon
content in the soil (OC) were determined. Further Crop Evapotranspiration (ETc) and Water use
efficiency were analyzed.

The ETc, varied between 2.34 and 4.84 mm/day and was highest during the development and late
stage of the growing season. The rainfall was able to cover the water crop requirements of maize in
all locations. Maize yield was highest at T5, followed by T4 and T2. Further, yield was strongly
affected by the clay content and soil type and resulted in significant differences between the
locations (Nyalgunga > Nyabeda > Vihiga). Other physical soil parameters (IF, BD, AS) did not
influenced the maize yield. IF varied between 1.3 and 9.1m/day. BD was generally low with an overall
mean of 1.16 g/cm³. The Aggregate stability was widely ranged and significantly higher in Nyabeda
and on T4. OC was significantly higher on T5. The results indicated that mineral fertilizers contribute
more to the increase of OC than organic fertilizers and that OC might not be the main driver of
aggregation in tropical soils. AS seemed to be positive affected by organic fertilizers but IF and BD
were not influenced by, nether organic or inorganic fertilizers. The results did not indicate any
differences between high and low fertility plots, nether in maize yield nor in any of the physical soil
properties.