When growing grain crops such as oats, wheat, barley, or triticale for hay, one of the most important things that affect yield of the crop is proper irrigation. Proper irrigation can be the difference between a 3 ton/acre and a 5 ton/acre crop and doesn’t cost much more than a mismanaged irrigation system.
Irrigation timing is critical with grain hay crops. I have broken growing season down into 3 parts that require different Irrigation rates.
Part 1: New Seeding. This stage begins even before the crop is planted. Here is when the subsoil moisture can be best built up. This time is during the early spring and usually the winter snows have melted and moisture is deep, but if it is not, than this is the time to correct that. If you are dry 1 foot down or more, irrigate one pass before you plant to push that moisture down. April 15th is when most of the water gets delivered so make sure your system is ready to go so your planting doesn’t get delay too much. After you have irrigated, wait a few days to dry the top 2-3 inches enough to plant, then get that tractor rolling and get the seed down. Seed will not sprout without moisture, so if the top soil is too dry, a quick irrigation with sprout that seed. I like to get the seed sprouted before applying fertilizer so the N doesn’t leach down below the roots. After applying fertilizer, it is important to get it water down into the soil, but too much water and the N will be pushed below the roots and will be useless.
Part 2: Growing Season. After the fertilizer is spread and the plants are 6 inches or so tall, they have enough root system and use enough water to not worry so much about leeching your fertilizer. I run my sets for 12 hours every 5-6 days during this time period and only shut off if a rain of more than a half inch falls. Some people make the mistake of shutting off after a too light of rain and have a difficult time recovering. When the plants are growing and it is hot and sunny, a lot of water is being pulled out of the soil and it is important to keep the soil damp but not saturated. Grains don’t recover well from droughty conditions. Keep the water flowing and keep that moisture in the ground.
Part 3: Preharvest. The last set before turning the water off before harvest is the most crucial in getting top yield, especially with short wheels on wheel lines. At this time the crop is quite tall and sucking huge amounts of water from the soil. Also it is during the hottest part of the summer and evaporation rates are high. If you have short wheels, you must time your last pass to occur right before the wheels won’t turn in the crop any more. I like to switch my nozzles to a size higher than what I ran during the growing season and run 24 hour sets my last pass to push that water all the way down and saturate the soil. By this time the fertilizer has been absorbed into the plant and so leeching is not as big of a concern. If you have 5′ wheels, your crop has 2-3 weeks more growth after your lines cannot roll any more so getting the soil saturated will delay your harvest and boast your yields, it will also lower nitrate levels. If you have pivots, this is not a concern and you can freely irrigate until whatever harvest stage you are aiming for.