Enhancing performance of maize-cowpea based cropping systems in coastal lowland Kenya through stress resilient varieties and soil moisture conservation practices

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 on-farm 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 N-fertilizer 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 DHO4-cowpea) 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 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 N-fertilizer 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-cowpea-intercrop 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.