Shrimp Health Management Extension Manual - Library - Network of ...

3.2. Pond preparation3.2.1. Risk factorsPond preparation is essential to reduce risks of shrimp disease outbreaks. The study has identifiedthe following risk factors that can significantly reduce the risk of disease outbreaks and improveshrimp production· Removal of bottom sludge, particularly in ponds stocking higher densities (up to 8 numbersper m 2 as in Nellore).· Ploughing of soil when wet (particularly at higher stocking density farms in Nellore).· Use of lime in pond preparation.The study noted that sludge left by the side of the pond (where it may drain back into the pond) mayconstitute a risk to shrimp health.Shrimp ponds with a history of disease outbreaks have a greater likelihood of future disease outbreaks,therefore special attention is required during pond preparation in such farms. Farms with poorbottom soil quality, particularly the presence of a black soil layer, will suffer crop failures. Theseare key factors and pond preparation measures are necessary to improve pond bottom conditions.3.2.2. Management guidelines3.2.2.1. Sludge removalCleaning the pond bottom is a very important pond preparation activity. The soil should be checkedfor the presence of black layer when it is in wet condition. If the soil is completely dried then theblack layer will turn to a lighter color due to oxidation, making it difficult to recognize that blacklayer in the soil. It is easy to remove the sludge when the soil is dry. In farms where stockingdensities are usually more than 6 PLs/m 2 (as common in Nellore district) and if a black soil layer ispresent, it should be removed completely. The sludge must be disposed away from the pond site, sothat it does not seep back into waterways, ponds, or cause other environmental problems. In farmswith lower stocking densities, such as in West Godavari district, it may not be necessary to removethe sludge, unless there was disease outbreak during the last crop. In such a situation extra precautionshould be taken. If the sludge is removed properly then management of the pond becomes easierduring high pH periods, a common problem in parts of West Godavari district due to low salinity,and high plankton growth.Sludge removal should pay attention to areas of the pond where there is a high accumulation oforganic matter from previous crops, such as feeding areas, and the side ditches in extensive farms.8