Shrestha, Madhav Kumar creator Lin, Chang Kwei Chairperson Edward, Peter Examination committee Chongrak Polprasert Examination Committee Upasena, Selawa H. Examination committee Boyd, Claude E. Examination committee Government of Australia Scholarship donor Asian Institute of Technology Fellowship Scholarship donor text series technical report th Bangkok Asian Institute of Technology 1994 continuing eng 206 leaves A series of six experiments was conducted to study the effects of pond bottom soil types on phosphorus (P) saturation level and its relation to P fertilization; to study the nutrient recovery potentials from bottom soils by rooted macrophytes and upland crops. Pond muds accumulate P in two forms; (1) adsorbed inorganic P and (2) deposited organic P. P adsorption in mud is related to cations (A13+ , Fe3+ , Ca2+) content in clay and clay content (%) in mud. can represent its adsorption capacity. P adsorption is slower below 5-cm depth and cation P adsorption capacity is a linear function of clay content (%) in mud. Therefore, level of P saturation (%) in mud can be calculated by initial cation P and clay content (%) in the top 5-cm of pond mud using the equation: P saturation (%) = initial cation P (mg/g soil) x 100 / P adsorption capacity (mg/g soil). The results show positive linear relationship between soluble reactive P (SRP) availability and mud P saturation level. and negative correlation between added P loss from water column and mud P saturation level. Biogenic P was a major source of P sedimenter, With a rate twice higher than that in direct adsorption of inorganic P in mud. Bioturbation facilitates release of loosely bound P (loose-P) and aluminum bound P (A1-P) but it also leads to adsorb iron bound P (Fe-P) and calcium bond P (Ca-P) in mud at pH 7-9. Increasing the SRP concentration in the water Column up to 0.3-0.4 mg/L is sufficient for the fish pong as higher SRP concentration will increase primary productivity, nor fish yield. The concentration of SRP can be achieved with a P fertilization rate of 0.2 g, 0.1 g and 0.05 g/m3/day and N:P ratios of 2:1, 4:1 and 8:1 when the level of P fertilization rate for tropical ponds in a semi-intensive system should be 0.2 g, 0.1 g and 0.07 g/m2/day (2 kg, 1 kg and 0.7 kg/ha/day) with a N:P ratio of 2:1, 4:1 and 6:1 for below 50%, 50-80% and above 80% P saturated muds, respectively, to compensate the P adsorption below 5-cm depth which is slow but continuous. Organic P deposited in pong bottom can be recovered by enhancing oxidation to mineralize organic matter by drying the pond at an optimal 20-40% moisture for two weeks. oxidation of pond mud certainly enhances the adsorption of mineralized P but, its rate and amount depend on P saturation level in mud. Once the partial saturation of P in mud increases, mineralized P released from organic matter to water column will be greater than mud adsorption, Rooted plants can mobilize the adsorbed P in mud. Due to frequent liming in pond preparation, a considerable amount of P is adsorbed by Ca ion. Plant roots are capable of extracting Ca-P from mud. Roots of semiaquatic taro crop is efficient to utilize Fe-P in mud in reduced environment P fertilization strategy based on mud P saturation level has been discussed. Procedure for estimating mud P saturation level and corresponding P fertilization relate to tropical semi intensive fish pong is suggested. A dissertation submitted in partial fulfillment of the requirement for the degree of Doctor of Technical Science, School of Environment, Resources and Development Thesis (Ph.D.) - Asian Institute of Technology, 1994 Fish ponds Fertilization Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B00319 http://203.159.5.9/ait-thesis/detail.php?q=B00319 171197 20260818094310.0