The health and productivity of shrimp ponds are critically dependent on proper pond preparation, including the maintenance of optimal pH levels. One essential step in pond preparation is the determination of lime requirement and its subsequent application, commonly referred to as liming. This blog will explore the steps involved in determining the lime requirement using Boyd's method and discuss various methods of liming, all while emphasizing safety precautions.

 

Importance of Liming in Shrimp Ponds

Liming plays a pivotal role in improving water quality, enhancing soil conditions, and facilitating a healthy environment for shrimps. The primary purposes of liming include:

• Neutralizing Acidity:

  Many ponds have acidic soils and water which can hinder shrimp growth. Liming helps neutralize this acidity.

• Improving Water Quality:

   Proper liming enhances water's buffer capacity, stabilizing pH levels and making the aquatic environment more conducive to shrimp health.

• Enhancing Nutrient Availability:

   By adjusting the pH, liming also aids in the dissolution and availability of essential nutrients, promoting better algae and plankton growth, which are crucial for shrimp diets.

 

Determining Lime Requirement

Several methods can be used to determine the lime requirement in ponds, with Boyd's method being one of the most straightforward. This method involves the following steps:

 

Boyd’s Method

1. Sample Preparation:

• Weigh 20 g of the sieved soil sample into a 100 ml glass beaker.
• Add 20 ml of distilled water to the beaker. Stir intermittently for one hour.

1. Initial pH Measurement:

• Measure the pH of the solution using a pH meter that has been previously standardized. Record the reading.

1. Buffer Addition:

• Add 20 ml of p-nitrophenol buffer to the above solution and stir intermittently for 20 minutes.
• Prior to measuring its pH, set the pH meter to pH 8.0 using a 1:1 mixture of p-nitrophenol buffer and distilled water.

1. Final pH Measurement:

• Read the pH of the soil sample (buffer/distilled water mixture) while stirring vigorously.
• Use the values of the soil sample pH in distilled water and soil sample in the buffered solution to obtain the liming rate from Table 1.
• If the pH of the soil in the buffered solution is below 7, repeat the analysis with 10 g of soil sample and double the liming rate.

 

Safety Precautions

• Handling Chemicals:

  p-Nitrophenol is toxic and carcinogenic. Potassium hydroxide is highly caustic. Always handle these chemicals with care, using gloves and protective eyewear.

• First Aid Measures:

  In case of contact with skin or eyes, flush the affected area with plenty of water immediately.

 

Conversion to Calcium Oxide

The liming material commonly used in ponds is calcium oxide. Therefore, it is necessary to convert the liming rate to calcium oxide value by multiplying the above rate with 0.56.

 

Methods of Liming

Liming can be performed through various methods, each suitable for specific conditions and requirements.

 

Over Dried Pond

This method involves uniformly spreading lime over the dried pond bottom, including dike walls. It ensures thorough mixing with the soil, leading to better pH adjustments.

 

Mixing with Water and Spraying

Lime can be mixed with water to create a slurry, which is then sprayed over the pond surface. This method is efficient and ensures even distribution across the entire pond.

 

Liming the Water Flowing into the Pond

Though less common, this method involves adding lime to the water flowing into the pond. It saves labour but requires careful monitoring to ensure adequate and uniform pH adjustment throughout the pond.

 

Application of Lime Based on pH Values

Soil pH	Qty of Ca(OH)2 (Kgs/ha)	Qty of Ca CO3 (Kgs/ha)
> 6	<500	<1000
5-6	<1000	<2000
<5	<1500	<3000

 

Conclusion

Proper liming is crucial for maintaining optimal pond conditions and ensuring the success of shrimp farming. By accurately determining the lime requirement using Boyd's method and applying lime through one of the described methods, shrimp farmers can enhance the productivity and health of their ponds.

At Aquabeats, we are committed to helping shrimp farmers unlock their full potential through innovative solutions and expert guidance. For more insights and support in shrimp farming, feel free to reach out to our team at Aquabeats Labs.