First we need to calculate the total water required. Let’s seen an example:

Consider we have 1.5 ha area and going to grow a cotton crop in the spacing of 1.5 m x 0.50m.  We are going to use inline dripper having a discharge capacity of 2 LPH (litres per hour so how to calculate the water requirement in drip irrigation?


Taking the given parameters,

 

We need to calculate how many plants are there in a given area?

Convert ha to sq.meter

1.5 x 10,000 = 15000 Sq.meter

Then,

=15000 / 1.5 x 0.5 (crop spacing)

= 20000 plants can be planted in the field

Now,

We are going to provide 2 litres of water to each plant, so

Total Water Requirement = 20000 x 2 (Total plants x dripper discharge )

=40000 litres or 40 m3/hr

So, we need 40m3 / hr water to irrigate 1.5 ha of cotton crop using emitters  in drip irrigation

 

Source: agriculturalinformation4u.blogspot.com