Response of water spinach

	Response of water spinach (Ipomoea aquatica) to fertilization with increasing concentrations of rubber tree latex wash water and biodigester effluent Ngo Tien Dung, Goat and Rabbit Research Centre Sontay, Hatay,Vietnam
Abstract A short-term growth study of water spinach (Ipomoea aquatica) plants was laid out in a completely randomized block design, replicated two times. The treatments arranged in a 2 x 5 factorial design were: biodigester effluent and rubber seed tree latex wash water. Both source of N were applied every two days at five levels (0, 10, 20, 30 and 40 kg N/ha) into baskets of 30 x 45 cm and 20 cm depth. The soil had 1.54% organic matter, pH 5.49 and N 0.1%. There was a significant interaction (P<0.05) between the studied factors. The height of water spinach plants in the effluent treatments were 27.3 and 42.0 cm with 10 and 40 kg N/ha respectively and were higher (P<0.05) than those from latex treatments (20.6 cm and 23.7 cm for 10 and 40 kg N/ha respectively). The growth rate of water spinach when effluent was applied tended to be higher than latex in all levels (P <0.05). In the effluent treatments, there were significant differences (P=0.001) in every level, with means of 0.84 and 1.52 cm/day in treatments from 10 to 40 kg N/ha. Biomass yields and protein content of water spinach increased linearly (P<0.02) with increasing levels of the effluent and latex wash water. At the highest level (40 kg N/ha of effluent) the biomass yield of water spinach reached 2.44 tones/ha and crude protein content reached 29.6% in dry matter. The dry matter of water spinach decreased linearly (P=0.001) as effluent level increased. According to the results of the present experiment, plant response to both types of source of N is dependent on the level and the type of fertilizer. It is suggested that the most promising method of fertilization could be by applying biodigester effluent at a rate of at least 20 kg N/ha. Further experiments including the possible variations in rubber tree latex wash water quality and field trials to confirm the present results are recommended. *Keywords: water spinach, Ipomoea aquatica, biodigester effluent, rubber tree latex wash water, soil*

Water spinach before applying effluent and latex wash water	Water spinach was applied biodigester effluent (after 28 days)	Water spinach was applied rubber trees latex wash water (after 28 days)

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