Just like managing dairy cows, there is a lot more to putting water on crops than it looks. Plus, what may seem like tiny, insignificant details throughout the process can have a tremendous impact on costs and productivity.
Intensifying demand for water today mean those details are more important than ever, said Washington State University Extension Irrigation Specialist Troy Peters at the 2019 Western Dairy Management Conference in Reno, Nev. To help dairy producers get them right, Peters offered 10 key tips:
Number 1: Don’t guess about when to run the water and when to shut it off.
“What we want everyone to do is collect and use and some sort of data to irrigate. There are a lot of varieties of data. One is the look and feel method, which is okay. The weather-based evapotranspiration (ET) estimate method is better. Soil moisture sensors are even better, and a combination of ET and soil moisture sensors is best of all.
“The amount of water a crop uses changes drastically. Early in the season it is very little. It peaks in July or August and then drops back in fall. So if we apply the same amount of water throughout the season we are probably over irrigating in spring, under irrigating in summer, and over irrigating again in fall. We really need to modify the amount of water we apply and respond to different weather conditions.”
Number 2: Move sprinklers close to the ground if possible.
“This can save a lot of water, so if you are in a situation where you don’t have enough water, getting closer to the ground can really help. These systems are much more efficient and operating a sprinkler at 12 to 18 inches off the ground as opposed to eight feet is huge, especially in windy, dry areas.”
“We don’t think about the amount of water that is lost in the wind, but it can be 20% to 30%. Rainbows are pretty things, but they aren’t what we want to see when trying to run an efficient irrigation system.
“Incidentally, dairy producers especially are often not concerned with efficiency. They have a lot of effluent water they need to get rid of, so they do the opposite of what I am saying. High pressure, big gun sprinklers are best at being inefficient, by about 60%, plus they have large nozzles that won’t plug.”
Number 3: When using hand lines and wheel lines, use the skip movement method instead of the taxi or wipe methods.
“Taxi is where we irrigate with every riser going down the field, then we move the empty pipe back to the beginning and start again.
“Wipe is where we irrigate with every riser going down the field, then we irrigate with every riser coming back, like a windshield wiper. This is the most inefficient and ineffective method. It applies way too much water at the ends of the field and it takes so long between irrigations that it creates water stress.
“Skip is when we irrigate using every other riser going down the field, then hit the skipped risers on the way back. You will have quicker recovery from stress following an alfalfa harvest, fewer issues with water losses due to deep percolation (overwatering), and less stress between irrigation events. It also takes about the same amount of work each move.”
Number 4: if you want to be efficient, move pivots slowly.
“Move them as slowly as possible until you start to see runoff at the end of the field. Then speed up just a little bit to avoid the runoff. The more water we apply per pass with the pivot, the less total time we have water sitting on the soil surface and exposed to evaporation.
“If we want to be inefficient then what we do is run things really fast so there is more evaporation and less opportunity for water to penetrate into the soil.”
Number 5: Till less if you can.
“If we can do no-till, strip-till, or limited tillage we can save time sitting in tractors and burning fuel, and it will reduce wear and tear on equipment. And every time we till, we destroy soil structure texture a little bit and we expose more soil organic matter to volatilization that turns it into CO2. It also exposes moisture in the soil to evaporation.
“Especially in places where you are struggling with water availability, you can see yield boosts by doing less tillage. That’s because trash on the surface serves as a mulch to protect soil from heat and wind evaporation.”
Number 6: Schedule time and budget money to maintain and repair your irrigation system.
“Fixing leaks, replacing nozzles, and replacing sprinklers, regulators, and gaskets is a must. And of course, be sure to service the pump. Decide to just do it. It’s a better approach than messing with everything all at once, and I think it saves time and money in the long run.
“Of course, you want to fix leaks and unplug nozzles and regulators regularly. Water losses due to leaks can be tremendous. A survey in Idaho found leak losses on Thunderbird wheel lines averaged 12% to 16%. On hand lines the average loss was 36%. That’s a lot of water, and it means you’re running pumps longer, but not getting the benefit of water that you could if the leaks were controlled. It is well worth your time and money to fix them.”
Number 7: Don’t let water freeze inside your system.
“This is a no-brainer. Water expands when it freezes and creates tremendous pressure, so it is going to break just about anything. Be sure to take the time to get all water out before freezing temperatures arrive, otherwise it is going to be an expensive mistake!”
Number 8: It pays to have your system designed by somebody who knows what they are doing.
“You’re just going to pay and pay and pay for bad irrigation system design, either in lost potential yield and quality, or in higher energy costs.
“Remember, the amount of electricity or diesel you use, is proportional to the amount of water you pump and the operating pressure of the system. It really pays to get everything designed and done correctly.”
Number 9: Pay attention to nozzle sizes.
“Irrigation uniformity is really important to profitability, and water flow rate from each sprinkler is highly dependent upon nozzle size. Don’t just toss on a replacement sprinkler that has a different nozzle size.
“The two greatest losses of water in irrigation systems are both invisible. One is wind drift and evaporation of water vapor; the other is deep percolation of water in the soil.
“The amount of water that comes out of nozzles depends upon orifice diameter and pressure. Just one step too high or low from the correct nozzle size can result in 40% to 50% more or less water coming out of the nozzle than we want.
“Nozzles also become worn. Depending on how dirty the water is that you’re pumping and what pressure you’re using, its abrasiveness will cause nozzles to wear prematurely and grow in outlet diameter.”
Number 10: If your field has significant slope or elevation differences, you need pressure regulators or flow control nozzles.
“Water, of course, flows downhill. Hilltops don’t get as much water as low spots. You’re going to see lower yields on high spots and swampy areas down in basins.
“If you have a center pivot on a very flat field with little elevation difference, a maximum of 10 to 15 feet in a quarter section, and a constant and reliable incoming pressure, you probably don’t need pressure regulators on your pivot.”
This article appeared in the February 2020 issue of Hay & Forage Grower on pages 16 and 17.
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