Comparative Study on the Effects of Bio-fertilizers, Organic and Inorganic Fertilizers on Growth and Yield Components of Cowpea (Vigna unguiculata)

Abstract

For optimum plant growth, nutrients must be available in sufficient and balanced quantity. Fertilizers are designed to supplement the nutrients already present in the soil. Increased crop production largely relies on the type of fertilizers used to supplement essential nutrients for plants. The study was carried out to determine the effects of bio-fertilizers produced from plant and animal waste materials such as saw dust, cow dung and poultry droppings inoculated with a fungus (Aspergillus niger) and organic and inorganic fertilizers on the growth and yield of cowpea (Vigna unguiculata). The experiment was conducted at the Department of Plant Science and Technology Nursery, University of Jos. The saw dust and the cow dung and or poultry droppings were mixed in a ratio of 30:1 and then autoclaved to remove other microbes from the substrates. The substrates were mixed with A. niger and water in line with standard method after which they were placed separately into a locally constructed bio-digester. The substrates (cow dung + saw dust mixture and or poultry droppings + saw dust mixture) were stirred daily, while they were allowed to be degraded by the fungus (A. niger). The process of degradation of the different waste materials lasted for a period of two weeks after which the nitrogen, phosphorus and potassium (NPK) contents of the bio-fertilizers were analyzed alongside that of organic fertilizers. After biodegradation process, the various substrates were used to amend the soil used for growing cowpea. Six treatments plus control with 5 replicates per treatment were used. The fertilizer types included; bio-fertilizer produced from cow dung-sawdust mixture (BCD), bio-fertilizer produced from poultry droppings-sawdust mixture (BPD), combination of BCD and BPD and organic manures produced from cow dung (CD) and poultry droppings (PD) and inorganic fertilizer (IF). Pots of soils that were not amended with any of the fertilizer served as the control. Plant growth and yield parameters of cowpea plant grown on soil amended with bio-fertilizers were measured and compared with those grown on soil amended with organic and inorganic fertilizers. Both bio-fertilizers and the inorganic manures affected growth parameters of the cowpea variety used at varying degrees. There was a remarkable increase in all the growth parameters for all the treatments over the control (Cowpea grown on soil that was not amended with fertilizer) with the exception of the cow dung manure (CD). The yield of the crop which was obtained from the combination of the two biofertilizers (BCD and BPD) gave the best yield with respect to the total weight of the seed per pot 169 g followed by BPD 129 g and BCD 127 g, while IF, PD, control and CD gave the percentage yield of 94, 85, 68 and 61 g respectively. Similar results were also obtained from other crop yield parameters considered in the experiment, where the combination of BPD+BCD gave the highest yield except in the case of the mean length of one pod, with IF giving the highest yield of 0.19 cm. The results of the present study reveals that to obtain optimum yield of cowpea, the combination of the bio-fertilizers produced from cow dung-saw dust mixture and poultry droppings-saw dust mixture should be employed in amending the soil used for cultivating the crop especially in soil lacking essential nutrients.