The effect of graded levels of biodigester effluent N on short term growth of water spinach (Ipomoea aquatica)

Krailas  Kiyothong

krailas@hotmail.com

Abstract

A  2x6 factorial in a completely ramdomized design arrangement with 2 replications was employed to study the effect of graded levels of N fertilization on water spinach (Ipomoea aquatica)  growth in a short term experiment (28 days). Soil and sand were evaluated as substrate for water spinach growth and the fertilizer provided 0,10, 20, 30, 40 and 50 kg N/ha. The fertilizer was effluent obtained after anaerobic fermentation of pig manure in a plastic biodigester.   

There was no interaction between substrate and level of N fertilization. The results indicated that soil revealed to be a better substrate than sand. Biomass yield, protein yield and growth response of water spinach to N fertilization was curvilinear and the best treatment (P<0.01) was a level of 50 kg N/ha. Biomass and protein yield  were 2.53 and 1.70 t/ha for sand and 2.86 and 1.97 t/ha for soil. 

It is suggested that N fertilization of water spinach can be as high as 50 kg N/ha when a biodigester effluent is a source of fertilization in integrated farming systems.

Key word: water spinach, growth, soil, sand, effluent, biodigestor, N