Now showing items 1-2 of 2

    • Article

      Influence of pyrite oxidation and soil acidification on some essential nutrient elements. 

      NV Golez & K Kyuma - Aquacultural Engineering, 1997 - Aquacultural Engineering Society (AES)
      Influence of soil acidification on some essential nutrient elements was observed experimentally during periodic leaching at 10-day intervals of pyritic soil materials. Pyritic soil in glass columns saturated with distilled water was treated under waterlogged or submerged and drained conditions. Waterlogged was inundated and had overlying water of 2-cm depth above soil surface. Extremely acidic soil conditions, caused mainly by oxidation of pyrite (FeS2), led to other serious problems. Results showed that strong acidification of soils influenced the solubility and availability of some nutrients. The loss of calcium (Ca), magnesium (Mg), zinc (Zn), and copper (Cu) was enhanced by acidification. Intense acid conditions also dissolved manganese (Mn), high amounts of which would lead to toxicity problems in plants and animals. As oxidation progressed, soil acidification increased and depressed availability of phosphorous (P), thereby, leading to the deficiency of this nutrient. Sodium (Na) and Chlorine (Cl) were leached out rapidly in both treatments regardless of soil acidification. The common problems associated with acid soil formation from oxidation of pyrite are fish mortalities and very poor response of the soil to phosphorous fertilization. For idle land or areas abundant in pyritic materials, soil acidification can be avoided by inundation with water to a depth of 2–3 cm, rather than draining and exposure, which lead to the formation of acid sulfate soil. Periodic leaching was found effective in reducing soil acidity although some essential nutrients were also removed. Therefore, fertilization during amendments is found to be of necessity.
    • Article

      Nitrogen and phosphorus utilization in the cyanobacterium Microcystis aeruginosa isolated from Laguna de Bay, Philippines 

      SF Baldia, AD Evangelista, EV Aralar & AE Santiago - Journal of Applied Phycology, 2007 - Springer Verlag
      Phytoplankton supports fisheries and aquaculture production. Its vital role as food for aquatic animals, like mollusks, shrimp, and fish cannot be overemphasized. Because of its contribution as a food source for fish, the growth kinetics of Microcystis aeruginosa, a dominant cyanobacterium in the lake, was studied. The regular occurrence of M. aeruginosa is experienced during the months of May to July or from September to November in Laguna de Bay, the largest freshwater lake in the Philippines. M. aeruginosa was collected from Laguna de Bay, isolated, and established in axenic conditions. Data on the growth kinetic parameters for nitrate-nitrogen and phosphate-phosphorus utilization by M. aeruginosa gave the following values: half-saturation constant (Ks), 0.530 mg N. L−1 and 0.024 mg P. L−1 respectively; maximum growth rate (μmax), 0.671. d−1 and 0.668. d−1 respectively; maximum cell yield, 6.5 and 6.54 log, cells. ml−1 respectively; nutrient level for saturated growth yield, 8.71 mg N. L−1 and 0.22 mg P. L−1 respectively; and minimum cell quota (Q0), 2.82 pg N. cell−1 and 0.064 pg P. cell−1 respectively. The low Ks value and high maximum growth rate (μmax) for phosphorus by M. aeruginosa would suggest a high efficiency of phosphorus utilization. On the other hand, the high Ks value for nitrogen indicated a low rate of uptake for this nutrient.