It depends on how deeply you really want to get into it. Lately I've been a little obscessed with the topic so here goes the cliff notes version:Miller_Low_Life said:So I'm here in Nebraska and we've had a string of 90's and 100's for about a week. We're supposed to have another week of this with no rain help. My question is that I've been watering every other day, putting 1/2 inch of water down each, am I over doing it? The grass is green but I'm worried I'm not letting it dry out enough to allow more root growth.
In short, you want to keep the rootzone soil water content between full field capacity (basically what the soil can hold before runoff) and maximum allowable depletion (basically how much water can be used by the plant and evaporation before the plant is stressed to an undesirable level). Irrigate to full field capacity only when soil water content falls to maximum allowable depletion.
Your cooperative extension can likely help you with a lot of the numbers for your soil type and provide ET data for amount of water used and rainfall data for what is added by nature. In Delaware we have a computer program that calculates all this stuff on the fly each day.
For example, my particular soil can hold about 3.65" of water in the rootzone (8") and so far I have set max allowable depletion to 40% of that (you have to observe the "crop" and make a judgment call for how dry is the point of undesirable for you - a golf fairway might have a different decision than a home lawn, for example. Typical ranges might be around 50% for high maintenance turf to as low as 30% for lawn turf). When the combination of rain and ET addition and subtraction of water content results in soil water content of only 40% of field capacity, I add the amount of water needed to bring the soil back to field capacity. So far this season I've needed to irrigate only once when there was no rain for about three weeks.
The objectives of all that monitoring and calculating is to avoid runoff from overwatering (affects water quality in our streams and bays), reduce disease pressure from excessive irrigation frequency and moisture, and maintain healthy, attractive turf.
If you don't want to go through all of that, I'd start by irrigating a standard 1" of water once a week. If the turf is drought stressed before the end of each week, add a second irrigation day to the week with a total amount based on ET data averages (which you can generally get from your cooperative extension). Continue to adjust irrigation amounts until the turf is only slightly drought stressed at the next irrigation event.