Abstract
A field experiment was conducted between August and October, 2014 at the Department of Microbiology to assess the effect of organic and inorganic fertilizers on the population and activities of Phosphate Solubilizing Bacteria (PSB) in the rhizosphere of maize variety BR9928DMRSR-Y. Three treatment groups were used in the study and these were: Groups which received applications of organic fertilizer (Poultry litter) alone, groups which received applications of inorganic fertilizer (NPK) and the third group which was the control (CON) did not receive any fertilizer application. A total of twenty-three bacteria were isolated and in-vitro screening was done for different phosphate solubilization activity. The study revealed that maximum population of total heterotrophic bacteria (26.8×109 CFU/g) was obtained with organic fertilizer (OM) treatment. Among the different PSB isolates, OMPSB had the highest bacterial count of 10.2×109. The lowest bacterial populations were obtained from IFPSB with 6.0×109 CFU/g. Out of the 23 PSB isolates, 18 were positive for phosphate solubilization with OMPSB8 showing the highest zone with 16 mm. Results showed that application of organic fertilizers enhanced the bacterial population and also showed increase in phosphate solubilization activities in rhizosphere soil compared to NPK and control treatments. This shows that organic fertilizers would be able to sustain the soil fertility for a longer period by meeting the demand of present and future generations. Key words: Treatment groups, population, phosphate solubilization, in-vitro screening
Highlights
Soil nutrient depletion has been a major challenge in Nigeria as a result of continuous cultivation of soils without adequate addition of external inputs
The negative effects of chemical fertilizers can be avoided by using organic fertilizers which have a positive effect on the Plant Growth Promoting Rhizobacteria (PGPR) - a group of rhizosphere bacteria found in association with roots which can enhance the growth of plant directly or indirectly by helping plants in nutrient uptake from rhizospheric soil (Mia et al, 2010)
To increase the natural fertility of the soil and develop new approaches to reduce the need for chemical fertilizers, PGPR are recognized as important factors in sustainable agricultural production as they may be important for plant nutrition by increasing the P uptake by plants, playing a significant role in the bio-fertilization of crops (Idriss et al, 2007) and serving as a natural source of fertilizers that improve the efficiency of soil and plants (Khalid et al, 2004)
Summary
Soil nutrient depletion has been a major challenge in Nigeria as a result of continuous cultivation of soils without adequate addition of external inputs. Maize has the following advantages compared to other cereals: High production, easy processing, easy digestibility, and they are less expensive It is an important source of carbohydrate, protein, iron, vitamin B and minerals (IITA, 2009) which according to IITA (2001) report, contains 80% carbohydrate, 10% protein, 3.5% fiber and 2% mineral. Application of chemical fertilizers can improve the nutrient balance of soils, which may lead to increases in crop yields, its continuous use is hazardous both to human health and the environment (Glick, 2003) This may cause plant toxicity (Nazar et al, 2012) and the bioaccumulation of trace metals in plants may pose a health risk consumed (Khan et al, 2015; Roy and McDonald, 2015). The rhizosphere supports large and active microbial population such as bacteria, fungi, nematodes, protozoa, algae and microarthrops (Raaijmakers and Weller, 2001) which play important roles in ecological fitness of their plant host (Kent and Triplett, 2002)
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