Effect of Uncomposted Organic Manures on the Plant Growth and Rhizosphere Microbial Population of Tomato Plants (Solanum lycopersicum L.)

Abstract

Compost is a form of organic fertilizer used in agriculture to promote the optimization of soil pH and nutrient management. Compost application can be used for sustainable agriculture because it has influence on the rhizosphere micro-flora which includes species of bacteria, fungi and other microbes. In this study, the effects of organic compost on the rhizosphere micro flora and the growth of tomato plants was continuously monitored. Three sets of tomato plants were planted under similar growth conditions in three experimental plots with varying soil-compost compositions as follows: soil amended with cow manure, soil amended with leaf litter and non-amended soil. Sample plants were harvested every 2 weeks and the physical characteristics including length of shoot, root and number of leaf were recorded. One gram of soil was removed from the rhizosphere for microbial analysis. The results indicated that plants amended with cow manure germinated faster, however growth rate gradually decreased after three weeks. Plants grown in soil amended with leaf litter compost and those grown in non-amended soil both germinated much later.  Growth rate however, continuously increased in plants grown in non-amended soil.  Bacterial colonization around the rhizosphere of plants grown in soil amended with both cow and leaf litter manure ranged from 10⁵ to 10⁷ CFU/g, with highest concentration at week 5 followed by a gradual decrease.  Microbial colonization in the rhizosphere of plants grown in non-amended soil also ranged from 10⁵ to 10⁷ CFU/g, but increased gradually with time.