Let us say we have have half an acre of vegetable crop and drip is installed with Venturi system. I need to supply let us say 4 kg of Urea through drip to all plants.
Now how do we calculate the amount of water required to dissolve 4kg of Urea to make sure each plant get the dosage?
Its impossible to give a specific answer as the amount of water depends on different factors: the soil type, the crop grown, and the type of irrigation system.
Different soil types have different water holding capacities. Light, free draining soils will need a lot more water than heavier soils. Different plants need varying amounts of water before they get stressed.
The trick with irrigation is to know how much water the specific plant needs, what the water holding capacity of the soil is, how much moisture mother nature is providing, and what the evapotranspiration rate is. Then you can work out how much water is needed through irrigation to keep the soil moisture between field capacity (the ‘full’ point) and the permanant wilitng point (where the plant is limited by lack of moisture and dies).
You may try to do some experiment primarily with the Venturi to understand how much is it passing
Try to record the delivery of the outlet of your pump where the Venturi is connected (with Ventury shut off), this gives the time taken for 1000 lts
Fill a drum with 100 lts of water
Repeat the measure of delivery of the outlet of your pump with Venturi switched on.
Try to understand how much of water has been sucked by Venturi from the 100 lts drum to draw 1000 lts of output.
This gives the percentage of fertilizer passing thru your water outlet going to drip irrigation.
Measure the requirement of water for your entire crop may be use Water meter.
And you know that you need 4KG of UREA to be supplied with this
Your delivery is 1000/min and it has taken 8 lts from the fertilizer tank (0.8% suction)
and you need total of 40000 lts for all your plants (40 mins)
and you wish to send 4kg of Urea in this 40,000 lts water.
Just mix the 4Kg Uria into 320 lts of water and supply with Venturi for next 40 mins, this will equally send your 4 kg UREA to entire farm.