Browsing by Author "Golez, Nelson V."
ArticleNV Golez -
Aquacultural Engineering, 1995 - ElsevierAcid sulfate soil formation was observed experimentally during leaching of pyritic soil material. Pyritic soil was saturated with distilled water in glass columns and treated under waterlogged and drained conditions. Waterlogged was inundated and had overlying water of 2-cm depth above soil surface. Temporal changes of various chemicals and physical characteristics of the soil and leachates were determined at 10-day leaching intervals. Results showed that strong acidification of soil in drained column but not in waterlogged was due to pyrite (FeS2) oxidation and the consequent production of sulfuric acid (H2SO4). As oxidation progressed, acidification influenced the pH, and increased the solubility of aluminum (Al) and iron (Fe). The loss of potassium (K) and sulfur (S) fractions was also enhanced by acidification. Strong acidic condition in drained columns slightly changed the texture of the soil to more clay, but was not enough to alter the mineral composition of the soil. Periodic leaching was found effective in increasing soil pH, but some essential nutrients were also removed, thus, the need for fertilization scheme during amelioration. In prospective ponds, pyritic soil should be tilled and dried for 2–3 weeks, then flushed and drained repeatedly until pH > 5 is obtained. Repeated lime incorporation should be done in the amelioration until high pH values are obtained. In existing ponds, formation of acid sulfate soil could be avoided by not excessively turning and exposing the pond bottom.
Book chapterNV Golez - In Training Handbook on Rural Aquaculture, 2009 - Aquaculture Department, Southeast Asian Fisheries Development CenterThis chapter aims to show simple methods for aquaculture and concentrate on most aspects of extensive, semi-intensive and intensive culture of shrimps in brackishwater from site selection, pond construction, pond preparation, rearing techniques, water management, harvesting, post-harvest handling, and economics.
Use of seaweed meals from Kappaphycus alvarezii and Gracilaria heteroclada as binders in diets for juvenile shrimp Penaeus monodon Two seaweed meals were tested as binders in shrimp diets. In the first study, Kappaphycus alvarezii or Gracilaria heteroclada in dry ground form were added to an isonitrogenous diet at 3, 5, 7 or 10%. The basal diet had 5% corn starch and 5% wheat flour as binders and served as the control diet. A second study used the seaweed meals at 5, 10 or 15% plus 5% wheat flour and a control diet containing 15% wheat flour (no seaweed meal). These two sets of diets were fed to juvenile tiger shrimp, Penaeus monodon, to assess the acceptability of the seaweed meals in terms of shrimp growth and survival. In both studies, diets with 10% G. heteroclada had the highest water stability after 4 h but differences among diets were minimal. In study 1, shrimp fed diets with 3% and 5% K. alvarezii and 10% G. heteroclada had the highest total biomass and those fed the diet containing 5% K. alvarezii the highest specific growth rate (SGR). Shrimp survival was highest with those fed 3% K. alvarezii and decreased as K. alvarezii was increased. Survival was not affected by the level of G. heteroclada in the diet. Diets with 3% and 5% K. alvarezii had the best feed conversion ratio (FCR). With a modified binder composition in study 2, total biomass and SGR of shrimp fed 10% G. heteroclada did not significantly differ from the control, nor from 10% K. alvarezii and 5% G. heteroclada. Diets with 5% and 10% K. alvarezii or G. heteroclada had the best FCR. Survival was highest among shrimp fed 5% G. heteroclada but was not significantly different from those of the control, 10% G. heteroclada and 10% K. alvarezii groups. Thus, as a supplement for wheat flour, up to 5% K. alvarezii or 10% G. heteroclada meal could be used with no adverse effect on growth. The use of seaweed meals as binder in commercial shrimp diets would minimize organic waste from the feed and would mean an additional market for seaweeds.