This publication provides direction on estimating soil moisture by the "feel and appearance" method; taking a some soil and rolling it up in a ball then squeezing it between your thumb and forefinger to form a ribbon and noting how it appears and feels. Compare what you see with photographs and/or charts to estimate percent water available and the inches depleted below field capacity.
Independent of which system or mix of systems a grower uses, irrigation management can be challenging. An irrigation program must match the changing demands of the crop with the water supplied.