Production and Application of High-nitrogen Compost Extract as Liquid Fertilizer for Leafy Vegetable and Microalgae

Abstract

This study aimed to produce high-nitrogen compost extract and applicate it to land plants and microalgae, a candidate crop for biofuel and high value-added material production, as a part of low-salinity compost production system. For this purpose, we selected komatsuna, a leafy vegetable, and Botryococcus braunii, a microalga, as the test species. Nitrogen-added compost, which was used as a deodorizing material for ammonia released from composting, had a higher amount of inorganic nitrogen than potassium, unlike general dairy cattle manure compost. The extraction efficiency of the fertilizer elements from nitrogen-added compost did not increase by extending the extraction time (5 min) or increasing the solvent ratio to 4, except for phosphoric acid. That of phosphoric acid increased with the solvent ratio up to 100. The moisture content discharged from screw press tended to be lower than that of the dairy manure slurry. In the culture of komatsuna, compost extract could be used as an alternative to chemical fertilizers by supplementing the deficient of phosphoric acid. In the microalgae, compost extracts could be also used as an alternative to chemical fertilizers although phosphorus deficiency was observed in the late stage. There was no significant difference in hydrocarbon content of B. braunii.