Role of Fermented Bio-extracts Produced by Farmers on Growth, Yield and Nutrient Contents in Cowpea (Vigna unguiculata (L.) Walp.) in Northeast Thailand

Abstract

ABSTRACT Many small farmers in Northeast Thailand have adopted the on-farm production of fermented bio-extracts as a supplement to, or replacement for, chemical fertilizers. They use bio-extracts either singly or in combination with other organic amendments in crop production. The aim of this study was to investigate the benefit of bio-extract combined with organic fertilizers and alone as a nutrient source for crop biomass and yield. In a pot trial, addition of bio-extract alone at the local farmers' rate and frequency did not increase either biomass or yield of cowpea as its nutrient contents were much lower than those in the chemical fertilizer and all organic fertilizer treatments, and did not supply sufficient amounts of nutrients for crop growth on the low fertility sandy soil. However, in field and pot experiments, addition of bio-extract with organic fertilizers significantly increased plant top dry weight and yield above that obtained with organic fertilizer alone. Animal-based bio-extract gave larger and more consistent yield response than plant-based extract. The lack of response of yield to plant-based bio-extract with organic fertilizer was evident on the higher fertility alluvial soil. It may be concluded that bio-extract enhances the effect of organic fertilizers on cowpea growth. However, it is not clear whether bio-extract enhances crop growth by supplying a significant source of microorganisms or by supplying soluble C and/or N substrate for microbial activity to accelerate decomposition rate of organic fertilizers and release nutrients for the crop production.