Integrated Soil Fertility Management Practices Effects on Soil Chemical Properties and Maize (Zea Mays L.) Yield in Machakos County, Kenya
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Date
2024-01
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Kenyatta University
Abstract
Most of integrated soil fertility management (ISFM) studies have been carried
out at plot level, resulting in recommendations with minimal application due to
the heterogeneity of smallholder farms in semi-arid Kenya. A research study
was conducted in four (4) seasons between 2016-2018 with the aim to determine
the effects of selected Integrated Soil Fertility Management (ISFM) practices
on soil chemical properties and maize yields at the watershed level. The ISFM
treatments included combinations of maize monocrop/pigeon pea intercrop
cropping system; cattle manure applied at 2 ton ha-1
; N-P fertilizer applied as
40 kg ha-1
of diammonium phosphate (DAP 18:46) and tied ridging (TR). A
completely-randomized design (CRD) was adopted with nine for the following
treatments;- (1) maize monocrop & No fertilizer (control) (2) maize monocrop
& DAP (3) maize monocrop, DAP & TR, (4) maize monocrop, DAP & manure
(5) maize monocrop, DAP, manure & TR; (6) maize/pigeonpea intercrop &
DAP, (7) maize/pigeonpea intercrop, DAP & TR, (8) maize/pigeonpea
intercrop, DAP & manure, (9) maize/pigeonpea intercrop, DAP, manure & TR.
Soil pH, carbon (SOC), Total nitrogen (TN) and phosphorus (P). Exchangeable
Potassium (K), Calcium (Ca), Magnesium (Mg), Sodium (Na) and micros
Manganese (Mn), Copper (Cu), Iron (Fe), Zinc (Zn), and maize yield data
collected was subjected to analysis of variance (ANOVA) using GENSTAT
version 15 and means separated using Duncan's Multiple Range Test at (LSD
0.05). Results showed that the effect of ISFM practices on soil chemical
properties and maize yield varied. Organic C, TN, Ca, Na, Mn, Cu, and Fe
significantly (p<0.05) increased due to imposed ISFM practices. The maize
yields were higher in short rain (SR) than long rains (LR). The treatment
combination DAP, manure, tied ridging with maize-pigeon pea intercrop was
best in improving soil organic carbon (0.79%), total N (0.1%). The application
of DAP, manure, tied ridging with sole maize resulted in organic C increase by
0.78% and total N by 0.093%. The treatment combination DAP, manure, tied
ridging with maize-pigeon pea intercrop achieved the maximum maize grain
yield of 2.10 ton ha-1
and 2.16 ton ha-1
in the SR 2016 and SR 2017 respectively,
while in LR 2017, maize grain yield was 2.03 ton ha-1
. Further, it resulted in the
most significant marginal yield increase of 0.12 t ha-1
. This increase raised the
maize grain yield from 1.56 t ha-1
to 1.68 t ha-1
in 2016 and 2017 SR,
respectively. This was attributed to the improved soil fertility of the watershed
due to the inputs and the N supply from the biological nitrogen fixation process
of pigeonpea. Farmers in semi-arid locations can only utilize 10% of the
suggested inorganic nitrogen rates if they employ a combination of manure and
DAP with tied ridging on maize-pigeonpea. Furthermore, it is necessary to
economically validate these ISFM practices before upscaling.
Description
A Research Thesis Submitted in Partial Fulfilment of the Requirements for the Degree of Master of Science in Integrated Soil Fertility Management in the School of Agriculture and Environmental Sciences of Kenyatta University January, 2024
Supervisors:
1. Benjamin O. Danga
2. Kizito M. Kwena