Effect of water hyacinth on biomass yield of spinach and nutrient availability

Decomposition of water hyacinth (Eichhornia crassipes) and its effect on spinach growth was studied in a Vertisol. It was fully decomposed within 30 days under laboratory condition and increased the available N, P and K content of the soil. No allelopathic effect due to water hyacinth decomposition was noticed on spinach in the field. Application of 120 kg N ha⁻¹ through urea increased spinach yield by 106%. Application of water hyacinth increased the spinach yield by 85 and 42% when incorporated in the soil in fresh (green) and dry conditions, respectively. Initially mineral N content of the field soil was higher (34.3 mg kg⁻¹ soil) when N was applied through fresh water hyacinth as compared to 24.7 mg kg⁻¹ soil with farmyard manure incorporation. It was concluded that water hyacinth could be used as an ex-situ green manure and is better than farmyard manure in terms of increasing the available plant nutrients in soil and dry matter yield of spinach.