Response of forage cassava alone or associated with water spinach to fertilization with biodigester effluent

 Dinh The Tung

 dinhthetung@yahoo.com

Abstract 

A field experiment was conducted during 25 days to study growth characteristics of a cassava (Manihot esculenta Crantz) stand alone or in association with water spinach (Ipomoea aquatica) on a grey podzolic type soil (pH 4.86, organic matter 2.33% N 0.12%). A 2x5 factorial arrangement design with two replication per treatment was used to study in addition fertilization level (0, 25, 50, 75 and 100 kg N/ha). The fertilizer was an effluent originated from biodigestors charged with pig manure. 

There was a positive influence of fertilization on soil organic matter and N content at harvesting with an average of all treatments with fertilizer, 4.66 and 0.28% and without fertilizer, 2.89 and 0.22% respectively. 

There was a positive response of crude protein content in foliage when cassava was cultivated alone than associated with water spinach (34.0 and 18.7%). Total biomass yield was slightly high when both cultivars were associated as compared to cassava growing alone (1.76 and 1.56 t/ha). Crude protein in cassava foliage increased as a consequence of increasing levels of fertilization (19.3, 23.4, 26.4, 28.8 and 32.8% respectively). There was a positive linear response (R² 0.82) of total biomass yield to level of fertilization. In contrast, the response of water spinach yield per se was curvilinear (R² 0.91). 

It is concluded that in cultivating conditions as described in the present study, growth of cassava is not improved when water spinach is associated to cassava at least in a short cycle of 25 days. Soil fertilization with effluents from biodigestors is highly recommended as a factor of improvement of soil and cassava biomass quality. 

Key words; Effluent, biomass, cassava, water spinach, foliage