Compost inoculated with Azotobacter sp: impact assessment on eggplant (Solanum melongena) productivity and soil nutrient status in Ghana

We assessed the influence of Azotobacter inoculated commercial compost on eggplant productivity and soil nutrient status in the semi-deciduous forest zone of Ghana. In randomized complete block design, eight treatments (Control, 2.5 t ha−1 compost, 5 t ha−1 compost, 100% recommended NPK fertilizer at 50 kg N, 30 kg ha−1 P2O5 and 30 kg ha−1 K2O, 2.5 t ha−1 compost+50% NPK, 5 t ha−1 compost+50% NPK, 50% NPK and 2.5 t ha−1 compost+100% NPK) were evaluated under field conditions during two cropping seasons. In the major season, fruit yield under 5 t ha−1 compost significantly outperformed 50% and 100% NPK and the control. The highest fruit yield (4480 kg ha−1) was obtained under 5 t ha−1 compost in the minor season. While the effect of sole compost was significant on fruit yield, there were also strong trends suggesting added benefits from 2.5 t ha−1 compost+100% NPK. Integrated use of compost and NPK increased shoot biomass over the control and NPK treatments. The compost had significant effect (p < 0.05) on lowering soil pH at the end of study. The highest soil exchangeable Ca and Mg were recorded under sole compost. The findings suggest good prospect for increasing crop yield through inoculating compost with Azotobacter.