Bio Organic Farming/Biological Control of Pests

摘要

Biofertilizers : Azotobacterand Azospirillum biofertilizers in non-legumes can replace 25 - 30 % of chemical Nitrogen when used in combination with chemical fertilizers. Phosphorus solubilizing bio fertilizers have been found to be solubilizing 10 - 15 kg soil Phosphorus per hectare per season.. Like Bacillus megatherium, Pseudomonas also acts as Phosphate solubilizers. VAM ( eg Glomus spp) acts as Phosphate absorbers. Mycorrhizal roots lack root hairs. The fungal sheath together with the hyphae extending to the soil absorb nutrients. The Hartig net acts as a liaison tissue between the fungal sheath and the host cells. Mycorrhizal habit increases the surface. Area of the root system and affords better intake of nutrients. It also prevents the root from exogenous pathogenic infections by creating mechanical barrier. PSB secrete many metabolites viz C02, H2S,H2S04,HN03and organic acid which are responsible for Phosphorus solubilizing . Apart from fixing atmospheric Nitrogen, Azotobacter and Azospirillum secrete auxins, vitamins and growth promoting substances and antifungal antibiotics. Azospirillum maintains a much more intimate association with host roots compared to Azotobacter. Azospirillum is predominant in soil having pH 4.5 to 7.5, while Azotobacter thrives well in a pH range of 5.8 to 7.8.While Azotobacter requires mediocre soil moisture for survival, Azospirillum requires higher moisture content.