Even though the winter landscape in may seem to be asleep, cool season forages are saying: “feed me.”
Dirk Philipp, associate professor-animal science for the University of Arkansas System Division of Agriculture, said that cool season grasses have two distinct periods of growth: one starts in late February and peaks in May, and the other in the autumn, peaking in November, when daytime temperatures are cool.
“Winter annual forages such as small grains like rye and wheat probably grow at high rates as well,” he said. “For them, fertilizer applications are particularly important, because now is the time jointing – tillering and stem elongation – starts.”
“The time for applying fertilizer on your cool season grasses, and grass-clover mixes is ideally now,” Philipp said.
Before applying any fertilizer, it’s important to have had the soil tested. While it’s still possible to test so late in the game, there are some consequences.
“It may result in sticker shock for the amount of nutrients needed or that you find your pH is not in check,” he said. The soil pH should be kept between 6 and 7.5 for most crops.
So what happens if the soil test shows phosphorus and potassium to be very low, pointing to an expensive purchase of nutrients?
“Don’t panic,” Philipp said. “Portion the applications out to ease the effect on your wallet if needed.”
Unlike nitrogen, phosphorus and potassium may be applied so that soil test levels keep steady over time. “So if you missed it this time, these nutrients are relatively immobile in the soil and will be available later on to subsequent crops or growing cycles,” he said.
A few things to keep in mind:
- Potassium is needed for the proper functioning of enzymes, water use and photosynthesis.
- If clovers are in the mix, potassium levels have to be kept in check.
- Phosphorus is less of a problem, but on pastures that are newly established from woodlands, applications might be needed, or when phosphorus hasn’t been applied for a long time. Phosphorus is essential for early root development, winter hardiness, disease resistance and drought tolerance.
When it comes nitrogen, always apply according to the recommendations, Philipp said.
“Available nitrogen can’t really be measured, so you have to rely on the lab prediction,” he said. “The lab can make much better recommendations based on your past fertilizer history if they have past records of your soil tests.”
Philipp said that when submitting your soil test, “Indicate clearly on the soil box what you plan to do with the field, yield expectations.”
There’s one more cost caveat. “In spring, soil temperatures are relatively low so microbial activity is relatively low as well; therefore, nitrogen cannot be mobilized as quickly as necessary for rapid plant growth, so grasses will have to rely on added synthetic fertilizer, so don’t skimp on the fertilizer applications.”