This is something way to complex for someone hundreds of miles away on the internet to begin to tell you what to do, but I can give you a few things to think about.
First, get your crop water use data, for your area. They usually have a chart that will give you the use per day going back at least a week, along with projected use the next few days. Compare that with rainfall you had, to see if you are gaining or losing moisture in the soil, and how fast. If you have an idea how much water your soils hold, you can figure out about when crops need water.
Another thing to consider is your normal rainfall pattern. For example, if you live where it turns dry in Aug, you might want to water some extra in July, to build up subsoil moisture, to get you through the dry spell. If you live in an area that gets 'almost' enough moisture to grow a good crop, you might be able to get by watering as you need to.
The one piece of advice I can give, is not to let yourself get too far behind. If you miss a rain or two, you don't want the far end of the field to be suffering, before you can get water to it. Some places take less than a day to get water across the whole field, other places, it might take almost a week. That needs to be factored in, as well.
Lastly, you might want to get your irrigation water sampled. There are areas that have enough lime in the water, that an average irrigation season adds enough lime, that no additional lime is necessary.
There are even places, where fertilizer has been over-applied in the past, that has high nitrate water, that gives the crop additional nitrogen through the irrigation water.
