Response of maize grain and stover yields to tillage and different soil fertility management practices in the Semi-Deciduous Forest Zone of Ghana
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Date
2015-03-30
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Abstract
A study was carried out using runoff plots and Decision Support System for
Agrotechnology Transfer (DSSAT) Crop Simulation Model to identify appropriate site-specific soil management practices which best conserve soil, nutrients and water for
increased and sustainable maize production. The 4-season experiment (2012 major, 2013
major and minor and 2014 major seasons) was a factorial in Randomized Complete
Block Design (RCBD) arranged in a split plot with 3 replications. The tillage treatments
(main plot) comprised no-till (NT), hoe tillage (HT), plough-plant (PP) and plough-harrow-plant (PHP) whilst that of the soil amendments (sub-plot) were control (no
amendment), 100 % NPK fertilizer (15-15-15) at recommended rate, 3 t/ha poultry
manure (PM) and 50 % rate of PM + 50 % rate of NPK fertilizer. The annual rainfall
erosivity over a 10-year period which was calculated using the Modified Fournier
Index (MFI) revealed a high erosion risk (559.24 MJ. mm/(ha.h.y)) in the study area.
The erodibility of PP plots was found to be significantly lower (P<0.05) (0.018
Mg.ha.h/(ha.MJ.mm)) than that of NT (0.024 Mg.ha.h/(ha.MJ.mm)). Runoff ranged
from 12.57 to 23.95 mm for NT and Bare, respectively. Predicted and measured soil loss
was least under NT (0.14 and 1.14 Mg/ha) and highest on Bare plots (4.00 and 20.88
Mg/ha). NT with the greatest erodibility values, resulted in low soil loss due to effective
cover management practices. Reduction in soil depth and water holding capacity
followed the similar trend as soil loss. Bulk density decreased immediately after land
preparation but increased by the end of the cropping season under PP, PHP and HT
whilst under NT it decreased. Total porosity under the different tillage practices were
sensitive to increases in bulk density in the order of HT>PP>PHP>NT. NT recorded
higher cumulative infiltration amount (2358 mm), sorptivity (103.38 mm/s
½
) and steady
state infiltrability (0.7 mm/sec) and the least cumulative infiltration amount (834 mm),
sorptivity (25.88 mm/s
½
) and steady state infiltrability (0.3 mm/sec) under HT. Ks
ranged from 4.93 to 12.75 cm/h in the order of PHP > HT > NT > PP but the highest
(17.04 cm/h) was obtained under adjacent fallow field. Ks was highest under 100 % PM
(9.75 cm/h) and least under 100 % NPK (4.32 cm/h) in the order of 100% PM >50 %
rate of PM + 50 % rate of NPK fertilizer> 100% NPK. The enhanced Ks under the
iv
combined 50 % rates of NPK and PM (i.e. [2.16 + 4.88 = 7.04] cm/h) was considered an
additive effect (7.32 cm/h). The highest soil moisture storage was recorded under NT
and PP. Over the three seasons of experimentation, stover and grain yield, differed
among the various tillage and soil fertility amendments and their combinations. Stover
yield under the tillage practices ranged from 4.19 to 5.39 Mg/ha for HT and NT whilst
that of the soil fertility amendments ranged from 4.22 to 5.22 Mg/ha for control and 100
% NPK, respectively. Maize grain yield under the tillage practices ranged from 1.25 to
1.55 Mg/ha in the decreasing order of HT>NT>PP>PHP and that of the soil fertility
amendments ranged from 1.19 to 1.52 Mg/ha in a decreasing order of 100 % NPK>50 %
rate of PM + 50 % rate of NPK fertilizer>100 % PM>Control. The low grain yield
observed during the study was due to the incidence of long dry spells and moisture stress
during critical stages of crop growth. The response of grain yield to different soil
managements was best when the different tillage systems especially NT and PP were
amended with combination of 50 % rate of PM + 50 % rate of NPK fertilizer. WUE
followed the same trend observed for above-ground dry matter and grain yield. N, P and
K uptake was better under PP and NT for maize biomass and HT for maize grain than
the other tillage treatments. Uptake was better under 100 % PM and 100 % NPK for
maize biomass and 50 % rate of PM + 50 % rate of NPK fertilizer and 100 % NPK for
maize grain. The recommended choice of tillage practices coupled with the combination
of NPK and poultry manure amendments for sustainable maize production in
smallholder farms was in a decreasing order of NT>PP>PHP>HT. NT with proper
residue management and plough-plant amended with combination of NPK and poultry
manure, enhanced soil physical properties and reduced soil loss. The DSSAT-CSM can
satisfactorily be used to predict maize yield under changing climatic conditions and has
provided a menu of sustainable climate–smart soil management options in the study
area.
Description
A thesis presented to the Department of Crop and Soil Sciences, Faculty of Agriculture,
College of Agriculture and Natural Resources, Kwame Nkrumah University of Science
and Technology, Kumasi, Ghana in partial fulfilment of the requirements for the award
of the degree of
Doctor of Philosophy
in
Soil Science