You can tell when to water by feeling the soil a couple of inches below the surface. If it feels cool to the touch but doesn't wet or muddy your finger, it's just the right time to water. If it's dry and dusty, you've waited too long. If it wets your finger, it's too soon to water. Such soils need to be watered less frequently than sandy soils, but slowly and for a long time.
Sandy soils hold only a little water .
They should be watered more frequently but for only a short time. When bulbs begin to enlarge You can tell when to water by feeling the soil a couple of inches below the surface. If it feels cool to the touch but doesn't get your finger muddy, it's just the right time to water. Never let the soil get dry and dusty. For the most part, putting vegetables under water stress will greatly affect your harvest.