WWW.WAS.ORG • WORLD AQUACULTURE • JUNE 2014 31 circles rather than evenly dispersed. Liquid lime suspensions can react with soil acidity more quickly because of the finer particle size. However, for terrestrial use, research has shown more frequent applications may be needed to maintain desired pH/alkalinity. Liquid lime suspensions can contain as much as 50 percent water and require specialized mixing and spreading equipment. Distributing lime suspensions evenly over the surface of a pond filled with water could pose a daunting challenge. Furthermore, because the fine lime particles are suspended and not in solution, they will settle out of the water carrier if allowed to sit for too long. Both pelletized lime and lime suspensions are typically much more expensive to use than good quality agricultural lime with an equivalent neutralizing effectiveness (Wurts and Masser 2013). Notes William A. Wurts, Ph.D., Cooperative Extension, College of Agriculture, Food Sciences and Sustainable Systems, Kentucky State University, P.O. Box 469, UKREC, Princeton, KY 424450469. www2.ca.uky.edu/wkrec/Wurtspage.htm References Wurts, W.A and M.P. Masser. 2013. Liming ponds for aquaculture. Southern Regional Aquaculture Center, Publication 4100. percent. The various quantities of each particle size grouping and their associated NE values are averaged to arrive at an overall NE rating. Liquid Lime Suspensions A minimum quality dry agricultural lime could have approximately 90 percent of the particles pass through a 10-mesh sieve and only 50 percent pass through a 60 mesh sieve. However, in liquid lime, greater than 90 percent of the limestone particles will pass through a 200-mesh sieve. These finer particles react faster to neutralize soil acidity quicker. But suspending very fine lime particles in water does not necessarily make them more effective. The particles are suspended, not dissolved, and will settle out over time. These particles must be distributed evenly over the soil surface to be treated. This requires specialized spreading equipment that could be too expensive and cumbersome to distribute liquid lime over the entire surface of a pond, especially one already containing water. The particles in liquid lime are much finer, react quicker with soil acid and their neutralizing value is high. Because of this, many assume less liquid lime is required to achieve the same results attained with coarser dry agricultural limestone. However, this is not true if the liquid suspension contains close to 50 percent water. A liquid lime suspension that is 50 percent water cannot contain more than 50 percent lime. The neutralizing value of a liquid suspension that is only 50 percent lime is reduced by half (NV = 100 × 0.5 = 50). If the neutralizing value of a dry agricultural lime application is 85, 1.7 (85/50) times more liquid lime is needed than the dry agricultural lime to effectively neutralize soil acidity. Pelleted vs. Agricultural Lime As the neutralizing value of an agricultural lime source increases, less lime is needed to achieve the desired soil pH. The average neutralizing value of agricultural lime in Kentucky, for all quarries, is 67. This value is used for making liming recommendations in Kentucky. Information about the neutralizing value of pelleted lime should be printed on the bag. If the neutralizing value of pelletized lime is higher than agricultural lime, less should be needed to achieve the desired results. For a neutralizing value of 85, 78 percent less pelleted lime would be needed than the bulk agricultural lime recommendation. Divide the average neutralizing value of Kentucky quarry lime by the neutralizing value of the pelleted lime (67/85). If the recommended application of agricultural lime is 4,000 lb, then 3,120 lb of pelleted lime would be needed. While less pelleted lime is required, the rate reduction is not substantially lower. Pellets and Liquid Suspensions or Finely Crushed Agricultural Lime? Pelletized lime may be easier to distribute than agricultural lime over small areas — especially if spread by hand for ponds already filled with water. But, because the fine lime particles are combined with a lignosulfonate binder and spread as pellets, pelletized lime is no more effective for reducing soil acidity than standard agricultural lime. The particle binder must break down before the lime particles are available to neutralize acidity. When the pellets break down, the lime particles are concentrated in small Do You Want to Feature in the Future of Sustainable Aquaculture? Study and Succeed with E-Learning Courses from the University of St Andrews and TheFishSite
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