ABSTRACT

Maize (Zea mays L.) production contributes to food security and income generation for many farmers, but productivity is constrained by soil infertility, with potassium (K) deficiency partly accounting for the huge gap between potential and actual yields. The over use of chemical fertilizer has also helped to destroy the soil structure caused pollution and the dead of many animals species.This study was aimed at evaluating the impact or effectiveness of the 11 strains of individual plant growth promoting bacteria on the growth performance and yield of maize in relation to NPK fertilizer. The experiment was carried out on the volcanic soils of the University of Buea in Cameroon. The experiment was setup as randomized complete block design with 16 treatments replicated four times Each experimental unit measured  4 x 4 m. experimental units and replicates were separated  by 1 m with 2 m  The maize seeds weretreated with the bacteria before planting and after one month the young plant  sprayed with the plant growth promoting bacteria. At the end of the project it was observed that the treatment of maize with the plant growth promoting bacteria increased vegetative parameters and reduced pest infestation as compared to control.

CHAPTER ONE

INTRODUCNTION

1.1 Back ground of the study:

The latest world population projections indicate that world population will reach 10 billion persons in the year 2057. This only shows that there is an increasing need of food production to feed the growing population.Maize is an important food crop in sub-Saharan Africa (SSA) that contributes significantly to food security and income generation for many smallholder farmers. However, maize production is constrained by various biotic and abiotic factors including inadequate mineral nutrition. Poor and declining soil fertility is a major challenge for crop production in SSA, with nitrogen (N) and phosphorus(P) as the most limiting elements .(Ngosong et al.,2022 )

Traditionally, fields have been left to fallow for a number of years, so that the natural vegetation can regrow and soil fertility can be restored. But with increasing population densities and associated demands for land, the practice of leaving land to fallow is no longer an option in many areas of sub-Saharan Africa. As a result, soil degradation processes have intensified. Soil nutrient mining is the most common form of soil degradation, and results in less crop productivity, less biomass and less soil cover, thereby exacerbating other soil degradation processes, such as erosion, acidification and the formation of hard pans (dense soil layers that are largely impervious to water infiltration and root growth). Soil degradation thus reinforces itself, leading to an increasingly complex set of constraints to crop productivity. Ultimately, soils become nonresponsive and plants growing on such soils are no longer able to capture nutrients applied, for instance in the form of commonly available fertilizers. Cause of this soil infertility in Africa (Leigh Ann winowiecki et al 2017).

Low soil fertility is directly linked to low productivity, food insecurity and rural poverty. Food insecurity and poverty, in turn, can cause rural-to-urban migration, increased food importation bills (which compete with investment in agriculturalist development), and an increased reliance of rural communities on remittances sent from family members living in towns or abroad. Hence, we stress the immediate need to reverse soil degradation before it becomes unachievable and many African smallholder farmers become locked in a poverty trap. (Sanchez (2015). 

Chemical Fertilizer NPK has been used for over long periods  to combat the problem of soil infertility but it has led to devastating effects such as the distruction of the soil structure, leaching in to surrounding water bodies and causing the dead of many aquatic animals and soil organisms.

Although soil microbial biomass comprises less than 5% of organic matter, it responds rapidly on changes in soil management and can be used as early indicators of changes in soil C and C sequestration (Kallenbach and Grandy, 2011). The use of  beneficial microorganisms have been a viable option to synthetic fertilizers over the years.  Beneficial microorganisms are closely associated with their living environment, and environmental changes can alter different microbial species. Thus, different crop plant species can selectively assemble various microbes in their rhizosphere, phyllosphere, and endosphere. Studies have revealed that the microbiota associated with plants is crucial in determining plant performance and health, because certain beneficial microbes improve plant growth and resistance to stresses (Pedrós-Alió and Manrubia, 2016).Eleven strains of Plant growth-promoting bacteria have been isolated from the rhizosphere of the maize plant with the capacity to inprove plant growth invitro, through various direct and indirect mechanisms such as; N-fixation, P solubilisation and induce systemic resistance as described by (Tchakounte et al., 2018). But more insight on the performance of the individual bacteria in the field is yet to be obtained.

1.2 Problem Statement:

   Poor and declining soil fertility is a major challenge for crop production in SSA, with nitrogen (N) and phosphorus(P) as the most limiting elements (Ngosong et al.,2022). Chemical Fertilizer NPK has been used for over long periods  to combat the problem of soil infertility but it has led to devastating effects such as the destruction of the soil structure, leaching in to surrounding water bodies and causing the dead of many aquatic animals and soil organisms. (Mortvedt et al 2014) Use of fertilizers may also lead to acidification and mineral depletion in the soil, and chemical burn to crops. DownfieldFarm.com. Chemical fertilizers can help in plant growth promotion but have no role in improving soil properties (Etesami et al., 2017). Their excessive use also results in environmental pollution due to bioaccumulation and bio-magnification of several toxic compounds (Margenat et al., 2018). Heavy metals like mercury, cadmium, and lead are natural radionuclides that get retained into plants through the soil and ultimately enter the food chain. Several diseases like stomach cancer, vector-borne diseases, and methemoglobinemia have been reported in infants and humans due to the accumulation of these pollutants (Katiyar et al., 2016).

Plant growth-promoting rhizo-bacteria (PGPRs) are an indispensable part of organic farming. They are found in the rhizosphere and play an important role in enhancing soil productivity, stimulating plant growth, and suppressing plant pathogens. Most potential and widely reported PGPR genera include Pseudomonas, Aeromonas, Klebsiella, Azoarcus, Enterobacter, Azospirillum, Clostridium, Azotobacter, Arthobacter, Rhizobium, Gluconacetobacter, Bacillus, and Serratia (Bhattacharyya and Jha 2012). They do not have any negative impact on the soil and humans. Eleven strains of Plant growth-promoting bacteria have been isolated from the rhizosphere of the maize plant with the capacity to inprove plant growth invitro, through various direct and indirect mechanisms such as; N-fixation, P solubilisation and induce systemic resistance as described by Tchakounte et al., 2018. But more insight on the performance of the individual bacteria in the field is yet to be obtained.

     1.3 Objectives

1.3.1 Main Objective:

3 To evaluate the impact of 11 strains of plant growth-promoting bacteria on the growth and yield of maize in relation to NPK fertilizer.

1.3.2 Specific Objectives

-To assess the impact of the individual strains of plant growth-promoting bacteria on the growth parameters of the maize plant.

-Toevaluate the impact of the individual strains of plant growth-promoting bacteria on the yield of the maize plant. yield.