Enhancing performance of maize-cowpea based cropping systems in coastal lowland Kenya through stress resilient varieties and soil moisture conservation practices
Abstract
Coastal lowland region of Kenya is prone to drought hence enhancing productivity of
maize-cowpea based cropping systems requires deployment of stress resilient varieties
and agronomic practices that enhance moisture retention. Studies were conducted onfarm
at Tezo location and on-station at Pwani University and Kenya Agricultural and
Livestock Research Organization Mtwapa, coastal lowland Kenya, in the short rains and
long rains of 2011 and 2012. The objectives were: (i) To identify cowpea varieties most
preferred by coastal farmers through participatory variety selection; (ii) To determine the
influence of drought stress on canopy temperature, chlorophyll content, growth and yield
of local and improved cowpea varieties; (iii) To determine the effect of variety and
insecticide application on pest damage and growth and yield of local and improved
cowpea varieties (iv) To determine the effect of intercropping maize and cowpea on soil
moisture content, canopy temperature, chlorophyll content, growth and yield of the
component crops; (v) To determine the effect of cowpea crop residue management on
soil moisture content, canopy temperature, chlorophyll content, growth and yield of
intercropped maize and cowpea; (vi) To determine the effect of different farmyard
manure levels on soil moisture content, canopy temperature, chlorophyll content, growth
and yield of intercropped maize and cowpea; (vii) To determine the effect of varying Nfertilizer
application on soil moisture content, canopy temperature, chlorophyll content,
growth and yield of intercropped maize and cowpea in coastal lowland Kenya. All the
experiments were laid out in randomized complete block design and replicated three
times. In all the experiments, data collected were subjected to analysis of variance using
SAS and means separated using the least significant difference (LSD) at p=0.05. In the
first objective, participatory cowpea varietal evaluation of 11 cowpea varieties was
conducted using criteria developed by farmers. Farmers’ cowpea selection criteria before
flowering and at podding were high grain yield, drought tolerance, early maturity, ease
of harvesting and leafiness. Kutambaa, KVU 27-1 and Nyeupe were rated top varieties at
these stages. Farmers’ selection criteria at maturity and after harvest included grain
yield, color, taste and cooking duration. KVU 419, Kaima koko and Nyeupe were rated
top varieties at these stages. In the second objective, the 11 cowpea varieties were
subjected to no water stress, water stress during the vegetative stage and water stress
during flowering. Water stress imposed at vegetative growth stage and flowering
reduced cowpea growth attributes (plant height, shoot dry matter, and leaf number),
ground cover and chlorophyll content, but increased canopy temperature, time to
anthesis, harvest index, grain yield and yield components (pod weight, number of pods,
grains per pod and grain weight) for most varieties. In the third objective, 11 cowpea
varieties were either sprayed with an insecticide or not sprayed. Pest damage levels at
vegetative, flowering, podding and maturity stages were over 50% in all varieties.
Insecticide application reduced pod damage and insect pest damage at vegetative,
flowering and podding stages. Insecticide application reduced grain yield by a range of
11.6% (Nyekundu) to 662.5% (Macho). In the fourth objective, cowpea variety Nyeupe
was either intercropped with maize variety DH04 or maize variety Lamu. Sole crops of
both maize varieties and cowpea variety Nyeupe were also evaluated. Sole cowpea plots
and maize-cowpea intercrop plots had higher moisture content than sole maize plots.
Intercropping reduced chlorophyll content, weed biomass, growth attributes, yield and
yield components of maize and cowpea, but increased canopy temperature and cowpea
nodule numbers. In the fifth objective, two intercrop systems (Lamu-cowpea and DHO4cowpea)
and three crop residue management options (no residue, surface mulch and crop
residue incorporation) were evaluated. Application of crop residues (incorporated or
mulched) increased soil moisture content and chlorophyll content, growth attributes,
yield and yield components of cowpea and maize, but reduced canopy temperature and
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cowpea nodule number. Crop residue incorporation outperformed surface mulching in
most plant attributes. In the sixth objective, DH04-cowpea and Lamu-cowpea intercrops
were subjected to three farmyard manure levels (0, 2.5 and 5.0 t/ha). Farmyard manure
application increased soil moisture content and groundcover, chlorophyll content,
growth parameters, yield and yield components of maize plants; however, it reduced
canopy temperature and all cowpea plant attributes. DH04-cowpea intercrop
outperformed Lamu-cowpea intercrop in most plant attributes. In the seventh objective,
DH04-cowpea and Lamu-cowpea intercrops were subjected to three inorganic Nfertilizer
levels (0, 30 and 60 kg N/ha). Application of N-fertilizer increased maize
chlorophyll content, growth attributes, yield and yield components; however, it reduced
these plant attributes canopy temperature and cowpea nodulation. Performance of maize
under DH04-cowpea intercrop was higher than under Lamu-cowpea intercrop.
Cowpea varieties most preferred by coastal farmers were KVU 419, Nyeupe, KVU 27-1
and Kutambaa. Water stress reduced cowpea growth, but enhanced grain yield and yield
components. None of the 11 varieties was resistant to insect pests, but varied in the
response to insecticide application. Intercropping cowpea with either DH04 maize
variety or Lamu maize variety was more productive than sole cropping. Surface
mulching and crop residue incorporation conserved moisture and enhanced crop
performance, with the latter being more beneficial. Farmyard manure application
enhanced soil moisture retention and yield performance of maize in maize-cowpeaintercrop
but decreased cowpea performance. Application of N-fertilizer reduced cowpea
growth and yield but increased these attributes in maize. Crop residue use and
applications of farmyard manure and inorganic N-fertilizers decreased canopy
temperature. It is advisable for farmers in coastal lowland Kenya to adopt stress resilient
varieties and integrate crop residue, farmyard manure and inorganic N-fertilizers in
maize-cowpea intercrop systems.
Publisher
University of Nairobi