Comparing the effect of biological amendments and chemical fertilizer on bacterial and fungal population

Abstract

Amelioration of degraded soils has triggered interest regarding alternatives to supply nutrient and improve microbial diversity through the integrated use of organic manure and biofertilizers. In this light, a screenhouse experiment set in a completely randomized design (CRD) with seven (7) treatments; Bacillus thuringiensis (5 ml); digestate (22.4 t ha-1); 50% of digestate + NPK 15:15:15 (11.2 & 3.1 t ha-1); Digestate + B. thuringiensis (22.4 t ha-1 & 5 ml); Digestate + B. thuringiensis + Glomus mosseae 22.4 t ha-1, 5 ml & 500 g); positive control (NPK 15:15:15) and negative control with no treatment, replicated three (3) times was done. This research was carried out in the screen house of the department of soil science and land management, Faculty of Agriculture, University of Benin, with the aim of evaluating the agronomic value of anaerobic digestate (derived from cattle rumen content waste), inoculants of B. thuringiensis and G. mosseae in comparison with chemical fertilizer (NPK 15:15:15), while determining its’ effect on soil microbial properties, growth and yield of tomato. The results showed that application of NPK 15:15:15 at a rate of 6.1 t ha-1 caused a significant decrease in number of leaves of the tomato plant with a total of 50 and 56 leaves/plant in pots treated with NPK 15:15:15, and a combination of digestate and NPK respectively at 8 WAT. At 8 WAT, total organic carbon of the soil was best improved in soil with a treatment of digestate, bacteria and mycorrhiza inoculum (61%), and was also significantly improved in the positive control (63%), with the pots with no treatments having the least amount of organic carbon (1.8%). Total nitrogen was highest in treatments of digestate and both inoculums at 5.7% and least in soils with a combination of digestate and NPK 15:15:15 (0.3%). Soil microbial population of bacteria and fungi increased by 20% and 43% respectively. These findings indicate that a combination of anaerobic digestate, B. thuringiensis and G. mosseae applied at 22.4 t ha -1, 5 ml and 500 g respectively is best suited for tomato cultivation and is recommended for optimum growth and yield of tomato in the study area.