Even Bigger Payoffs For Water Management In Wet Years

Picture courtesy of Amy Harsh.

I had the opportunity to visit with one of our long-time customers concerning his water management needs for the 2019 growing season. He told me that because of the wet conditions this year, he didn’t think he would be irrigating as much and wasn’t sure he would see as much value in his water management systems as he had in drier years. I told him that I could certainly see how when it rains every day and most of your fields are under water, it’s hard to be too concerned about needing to irrigate. But, it’s the wet years like this when precision water management really pays.

 In the drier years when rain is infrequent or nonexistent, we often have to run the irrigation system continually to try and keep up with the water demands of the crop. In those years the sensor data is nice but the reality is the irrigation system will just need to keep running regardless of what readings we get. In wet years it’s totally different.

 The biggest share of the sensors that get placed this year will be put into soils that are at or near field capacity. Because of that, we have a great data set to start the year. When it’s dry, we sometimes never achieve field capacity without Mother Nature’s help, so it can be difficult to accurately establish those baselines. In wet years, the water management system is technically a more accurate and more reliable tool to use to help make water management decisions.

 Additionally, since the profile is full and we can see what’s happening underground we can use that information in our decision-making process. One of the key dynamics used in soil and water management is that water is always moving from the wetter areas of the profile into the drier parts of the root zone. As the roots and atmosphere take water out of the top of the soil profile and dry it down, water moves up from the wetter parts of the zone to replace it. With a precision water management system that is managed by professional agronomists, you can see that happening and use that stored water to help hold off irrigations early in the year. I’ve seen many growers error by making a decision on what they see happening in the top 4” and not consider what is below that. In the dry years, we start without a full profile. Since there is little water stored deeper in the zone you don’t see that movement. But regardless, you need to be able to measure and monitor that effect for it to be of economic value.

 Another thing that happens in wet years is crops don’t develop healthy deep root systems. If the soil stays wet in the top part of the profile the plants have no reason to develop roots deeper into the soil. These shallow roots then become a challenge when it comes to water management. In drier years it’s not unusual to see root development through 3 feet. But in wet years, we often don’t see root activity much below 1 ft. What happens then is our storage capacity in the one-foot zone is much more limited and we need more frequent irrigations with less application on each pass. We can make those adjustments but the only way to know how deep the roots are actively pulling water from the soil is to have a precision water management system on the field. Also, it’s important to know how much water is in the root zone so you can use the rain forecasts to help make irrigation decisions. Knowing the percent changes of rain in a wet year is helpful, but unless you know how much room you have for the precip it’s difficult to decide when, how much or even if you should irrigate. A well-managed precision water management system gives you all the data you need to make those decisions.

 In almost every irrigated field, regardless of how wet it is now, growers will have to make a decision on the need to water at some time during the growing season.  If you have a professionally managed system you can look at what’s stored in the soil, how much is being withdrawn on a daily basis, what is forecasted to be used in the next 7 days, and decide if it makes economic sense to irrigate. Without a system measuring the soil water content and crop water uptake, growers will error on the side of applying water that is not needed. When it’s been wet, and there isn’t a system for providing daily soil water, weather, and professional water agronomics, overwatering becomes an even more frequent problem. Often, a grower’s mindset is, “it hasn’t rained for quite a while now and it must be getting dry so I better start it up.” This leads to overwatering which causes problems because the roots tend to stay in an anaerobic soil environment for a longer period of time. This increases root disease and decreases the ability of the plant to produce sugars. Plus, each inch of water that is applied, and not used by the plant, leaches 8 lbs. of Nitrogen (N) out of the root zone. That N loss either needs to be replaced or we resign ourselves to 5-8 bushel less yield.

 When it’s been wet we will often have extreme water variability in the field because of variability in texture and topography. If you look at the fields around you today you will see that parts of the field are underwater, and parts of the field look almost dry. So, when it comes time to irrigate, how do you deal with that? Variable rate irrigation, a key component of every professional water management system, allows you to adjust the water application in those wet years so we can cut back on the water applied on the wet parts of the field and maintain or increase it on the drier parts.

 All in all, it’s easy to see how valuable a professionally managed irrigation scheduling system can be even in years with abundant rainfall.

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