Some of the podcasts talk about giving certain varieties of plants so many inches of water a week. I guessed it was the same amount of rainfall as an inch of water. But how to translate that into a unit of measure I understand.
Let’s just do it imperial and calculate the other way 1″ x 12″ x 12″ = 144 sq inches of water for an inch of rain falling on a square foot. Using the converter cubic inches to litres is 2.4 liters per sq foot.
I have two watering cans, one is 6 liters/1.5 us gal and the other 10 liters/ 2.6 us gal
The six liter normally holds five so I don’t slosh it all over the place. 5 liters will water 2 sq foot and the bigger can will do 4.
Before I go pouring all that water into the beds, they are filled with coir, compost and have a high organic/soil ratio, so the bed will be able to hold more water than you usual soil.
I normally push my finger in and you can feel if it is dry, moist or wet. Water as required.
The other option is to use blumats. They are relatively expensive in the UK £46 for 12 so I’ve tried copies from China or £12 for 12. These are touted as high tech watering system and in fact is ancient.
If an unglazed pot is sunk into the ground and filled with water, it will only seep out into the soil when the soil is drier than the outer face of the pot. The irrigation pots were called an olla, but you can just standard teracotta pots and some silicon sealant. Those ancient folk had a few good ideas.