Potential use of plant growth promoting rhizobacteria in organic broccoli (Brassica oleracea L., var. italica) production.

The continued use of chemical fertilizers and manures for enhanced soil fertility and crop productivity often results in unexpected harmful environmental effects, including leaching of nitrate into ground water, surface runoff of phosphorus and nitrogen run-off, and eutrophication of aquatic ecosystems. Integrated nutrient management systems are needed to maintain agricultural productivity and protect the environment. Microbial inoculants are promising components of such management systems. Field experiments was carried out to determine effects of plant growth promoting rhizobacteria (PGPR) [Bacillus cereus, (N2-fixing), Brevibacillus reuszeri (phosphate solubilizing), and Rhizobium rubi (N2-fixing and phosphate solubilizing)] on growth, chlorophyll content, yield and ionic composition of leaves of broccoli. The results showed that PGPR strain treatments stimulated plant growth and resulted in significant yield increase. Inoculation of broccoli plant roots and rhizosphere with PGPR strains also improved significantly uptake of mineral elements. The results of this study suggest that Bacillus cereus, Brevibacillus reuszeri and Rhizobium rubi have the potential to increase the yield, growth and nutrition of broccoli plant under organic growing conditions.