Aquaculture NCII

1. Draining, Harrowing
and
Drying

2. Objectives:
Discuss pond draining, harrowing
and drying.
Enumerate the purposes in pond
draining, harrowing and drying.

3. Draining
-to draw off (a liquid) by a
gradual process

4. Three types of Draining the Pond
 top drain
-about 10 - 30 % flush out of the total volume of the
water inside the compartment.
 Half Drain
-about 50% flush out of the total volume of the water
inside the compartment
 full/total drain
- flush out 100% volume of water

5. Four types of Draining the Pond in
terms of Process
flushing
-to flow the water outside the pond compartment
in the rush by opening the water gate.
siphoning
- is used to refer to a wide variety of devices that
involve the flow of liquids through tubes without
being pumped, and powered only by gravity.

6. suctioning
- is the flow of a fluid into a partial vacuum,
or region of low pressure by using a suction
machine such as pump or vacuum.
decantation process
- to pour out, transfer, or unload as if by
pouring

7. Siphon principle

8. Harrowing (Soil Tilling)
 - is simply turning over and breaking up the soil. Exactly
how deep you till and how fine you break up the soil
depends on your reason for tilling. To make the task of
tilling easier, you can purchase or rent an engine-
powered tiller from a garden supply center. These tillers
are great for large areas, but if you only have a small area,
try a cultivator fork or a deep spader or cultivator to
loosen up compacted soil.

10. Why You Need to Till:
 Soil becomes compacted over a period of years from rain and
foot traffic.
Loosens and aerates the top layer of soil or horizon, which
facilitates for the next operations
Helps mix harvest residue, organic matter (humus), and nutrients
evenly into the soil
Mechanically destroys weeds.
Dries the soil before seeding (in wetter climates tillage aids in
keeping the soil drier).

11. Drying:
is a mass transfer process
consisting of the removal of water
or another solvent by evaporation
from a solid, semi-solid or liquid.

13. Purposes of pond drying
 1. to eradicate fishpond pests, predators and
competitors
 2. to hasten the chemical decomposition of organic
matters deposited so that nutrients will become
available for the growth of fish food in the fishpond
 3. to totally harvest the fish stock
 4. to kill disease causing organism

14. “Dried until the soil cracks or when it is
firm enough to hold one's weight
without sinking more than 5 cm on
walking over the surface”