By Steve Melvin
Key Takeaways
Check soil moisture first — Fields may have more stored water than expected.
Pre-irrigate only when needed — Use pre-irrigation only if the drill cannot place seed correctly.
Irrigate after planting in dry soils — Post-planting irrigation can help ensure strong emergence.
Expect rapid water use — Higher seeding rates and faster canopy closure will increase water demand quickly.
Use full-canopy scheduling principles — After full canopy, most crops use similar amounts of water each day.
Prioritize vegetative growth — Fully irrigate during vegetative stages to maximize forage yield.
This year, hay and grass in pastures are in short supply across much of Nebraska, and many farmers are turning to annual forage crops under their center pivot to fill the gap. The big question on everyone’s mind is straightforward: We know how to irrigate corn and soybean, but how do we irrigate annual forages in dry years using the least amount of water while still getting a good stand and strong yields?
The good news is that with the right strategy, annual forages can be established successfully and produce excellent tonnage — even when irrigation water is limited.
Fields May Have More Water Than You Think
One of the first steps is to evaluate how much water is already in the soil profile. Fields that were irrigated last year — especially those watered late into the season — often start the new year with more stored soil moisture than expected. This stored water can significantly reduce the amount needed from irrigation.
Soil type plays a big part in the amount of water that may be stored in the root zone. Silt loam soil may have over 6 inches, while sandy soil may have only about half that much. Sandy soil surfaces also dry out quicker, which can cause germination problems with the small seeded forages that are planted at an inch or less deep in the summer months. Corn is usually planted about 2 inches deep in the spring when the days are cooler and less drying than in June, when many summer annuals are planted.
A soil probe or shovel is the best tool for checking moisture before making any irrigation decisions. Crops use soil water from the surface layer first and then move deeper into the soil profile. When rain or center pivot irrigation rewets the soil, that water starts at the surface and moves downward. The goal is to identify where the soil profile is dry and where it is still moist.
Source : unl.edu