Contrary to what seems to be the popular opinion on Social Media, I hate to tell you that the 2017 crop is not in the books. Did we make progress and set ourselves up for an easier rest of the year from an irrigation standpoint? Absolutely! But, we are not done with irrigation for the year, and I think it is fairly simple to explain why.
I have talked all year about how the AquaSystems Moisture Probes add clarity to our situation, and after this rain is no different. For those of you in the North, we see a full profile for the first time of the season. Even fuller than we saw in June when the probes were installed. But, while we can rejoice in a probe that is indicating a soil that is at capacity this week, we also need to remember what that means. For those of you in the North, we continue to see a crop that has struggled to establish the root profile under it that we want. 20”-24” of roots capture a lot of what is under this corn, and even with a full profile, that does not give us more than 4” of available water for our corn crop.
For those of you across the central portion of Nebraska, there has been no rule of thumb this season. Spotty rains have meant very different things for each of you. But what I can also deduce across this portion of the state is a crop that needs more water to finish than what we have in our profile. Now, I know some of you are going to tell me how much rain was in your gauge this week, but the soil probe doesn’t lie. As I look at a field near Utica with 40” of active roots under it, I see a crop with 5”-6” of demand left for the year at a minimum, and 4” of available water left in the root zone. High-intensity rainfall events have meant that infiltration didn’t keep up with rainfall, and where you were at with your soil profile and irrigation may have meant that you had water leave your field that you wish you had captured.
And so my take-home for the day is this. What our needs for the rest of the year vary by our crop stage. Corn is still going to need 4.5” to 7” depending on where we’re at in development. Everybody’s soybeans are still going to need 6” or more of water to finish out the season. I have yet to see a moisture probe that indicates we are done. But we have some folks that are near that point. My one point of caution to you is that we need to remember the energy that the plant spends bringing moisture up from the bottom of our profile. Even when we hit that magical threshold of Available Water surpassing Water Needs, we don’t get to quit for the year. Monitoring the plant’s water use at each root zone and watching for the plant exhibiting stress does not end until physiological maturity. The end of your job as an irrigator may or may not be close, but your job as a manager of water doesn’t end for at least another 40 days.