The study was aimed to evaluate water properties in trench of land use types of Acacia Hybrid and Melaleuca Cajuputi at U Minh Ha zone, Ca Mau province. The study was conducted on two soil types of deep acid sulfate and shallow acid sulfate. For each soil type, water properties were examined at two area levels with over 10 ha and less 10 ha. The study results showed that pH was very low at both land use types of Acacia Hybrid and Melaleuca Cajuputi, EC and DO had not affected yet the

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... . On the contrary, COD and BOD5 exceeded the regulations about water surface quality, and COD at land use forest of Acacia Hybrid tended to be higher than that of Melaleuca Cajuputi. They were not different about Fe and Al. The concentration of Fe was always higher than regulations about water surface quality, except Fe in deep acid sulfate soil at land use forest of Acacia Hybrid. H2S was lower than regulations about water surface quality for aquatic animal conservation. But N-NH4 + exceeded the limit, and N-NH4 + at land use forest of Acacia Hybrid was often higher than Melaleuca Cajuputi.