474
interaction with rhizobia should be a suitable character for selection of cowpea
genotypes for plant breeding programs (Gomes et al. 2015).
Maize (Zea mays L.) is one of the most essential cereal crops in Kenya. It is a
staple food for above 90% of the Kenyan population (Wambugu et al. 2012).
Although food security in Kenya usually depends on adequate supplies of maize to
meet the local demand, maize production has declined over the years. The downward
trend has been attributed to depleted soil fertility (mainly phosphorus, nitrogen,
potassium) due to lack of application of adequate fertilizers and poor soil health
management practices (Onono et al. 2013). A change in soil management practices
can help reduce the excessive use of mineral fertilizers especially P and N. This
includes inoculation with beneficial soil microbiota such as AMF and inclusion of
leguminous crops such as cowpea in the cropping systems.
Cowpea (Vigna unguiculata (L.) Walp.) is an important multipurpose legume
grown in Kenya mainly by smallholder farmers, among other legumes, such as
common bean and pigeon peas (Ondieki et al. 2017). It is a major source of
income and supplements nutrients such as dietary proteins, vitamins and fibre.
Cowpea has the ability to establish symbiosis with rhizobia, which enhances nodulation and the uptake of nitrogen through BNF, promoting plant growth and productivity (Mwendwa and Giliba 2012). The crop can thus be grown in mixed
intercropping systems without the need for application of chemical fertilizers
(Ondieki et al. 2017).
One way of sustainably improving crop production in smallholder farms is
through promotion of healthy plant-microbe interactions. To enhance such interactions in smallholder farming systems, three critical elements should be considered
holistically within the scope of increased agroecosystem functionality. These
include the soil environment, crop genotype and microbial isolates. In this study, we
hypothesized that soil quality and crop genotype would significantly affect nodulation, AMF colonization and growth of locally cultivated maize and cowpea crops in
semiarid areas of Eastern Kenya. Our specific objectives were (i) to isolate and
characterize native cowpea rhizobia using morphological and biochemical characteristics, (ii) to determine the effect of genotype and soil characteristics on cowpea
nodulation and growth and (iii) to determine the effect of maize genotypes and soil
characteristics on AMF colonization and growth.
2 Materials and Methods
2.1 Study Site
The study was conducted in smallholder farms in the semiarid areas of Embu (near
Machang’a Primary School, latitude 1°10′S, longitude 37°47′E) and Kitui (near
Kathiani Primary School, latitude 0°46′S, longitude 37°39′E) counties in lower
E. M. Njeru et al.
interaction with rhizobia should be a suitable character for selection of cowpea
genotypes for plant breeding programs (Gomes et al. 2015).
Maize (Zea mays L.) is one of the most essential cereal crops in Kenya. It is a
staple food for above 90% of the Kenyan population (Wambugu et al. 2012).
Although food security in Kenya usually depends on adequate supplies of maize to
meet the local demand, maize production has declined over the years. The downward
trend has been attributed to depleted soil fertility (mainly phosphorus, nitrogen,
potassium) due to lack of application of adequate fertilizers and poor soil health
management practices (Onono et al. 2013). A change in soil management practices
can help reduce the excessive use of mineral fertilizers especially P and N. This
includes inoculation with beneficial soil microbiota such as AMF and inclusion of
leguminous crops such as cowpea in the cropping systems.
Cowpea (Vigna unguiculata (L.) Walp.) is an important multipurpose legume
grown in Kenya mainly by smallholder farmers, among other legumes, such as
common bean and pigeon peas (Ondieki et al. 2017). It is a major source of
income and supplements nutrients such as dietary proteins, vitamins and fibre.
Cowpea has the ability to establish symbiosis with rhizobia, which enhances nodulation and the uptake of nitrogen through BNF, promoting plant growth and productivity (Mwendwa and Giliba 2012). The crop can thus be grown in mixed
intercropping systems without the need for application of chemical fertilizers
(Ondieki et al. 2017).
One way of sustainably improving crop production in smallholder farms is
through promotion of healthy plant-microbe interactions. To enhance such interactions in smallholder farming systems, three critical elements should be considered
holistically within the scope of increased agroecosystem functionality. These
include the soil environment, crop genotype and microbial isolates. In this study, we
hypothesized that soil quality and crop genotype would significantly affect nodulation, AMF colonization and growth of locally cultivated maize and cowpea crops in
semiarid areas of Eastern Kenya. Our specific objectives were (i) to isolate and
characterize native cowpea rhizobia using morphological and biochemical characteristics, (ii) to determine the effect of genotype and soil characteristics on cowpea
nodulation and growth and (iii) to determine the effect of maize genotypes and soil
characteristics on AMF colonization and growth.
2 Materials and Methods
2.1 Study Site
The study was conducted in smallholder farms in the semiarid areas of Embu (near
Machang’a Primary School, latitude 1°10′S, longitude 37°47′E) and Kitui (near
Kathiani Primary School, latitude 0°46′S, longitude 37°39′E) counties in lower
E. M. Njeru et al.