A little bit of nitrogen fertilizer on the right alfalfa fields is well worth the cost, say Steve and Randy Senn, Ephrata, WA.
The brothers have been selectively applying 5-7 lbs/acre of N between cuttings since the 1990s.
“We target the older stands that seem to be running out of gas,” says Steve. “We're very pleased with the response.”
The nitrogen usually goes on after the second and third cuttings. It's applied through center-pivot sprinklers with the first watering after baling. Visual cues and under-performance are the criteria used to determine which stands need the nutrient.
“Although we haven't done any double blind studies, we see a definite improvement in stands that get the fertilizer,” says Steve. “The worse off they are, the better they respond.”
The fertilizer is actually a liquid blend that also includes phosphorus, potassium and micronutrients. Applying the between-cutting blend hasn't significantly increased the Senns' fertilizer costs. They just shifted some of their spring and fall fertilizer allocation to summer, cutting the phosphate budget a bit to pay for the nitrogen.
Steve says the more-targeted approach on selective fields seems to give them more bang for their buck.
“For a relatively small investment, we've been very impressed with the return,” he says.
Is applying nitrogen to established alfalfa stands really a wise move?
It depends on the cost, production level and the age and condition of the stand, says Gary McCourt, field representative for Western Farm Services (WFS), Pasco, WA.
Before investing in any fertilizer program, McCourt recommends preseason soil tests to establish a nutrient baseline. Soil and petiole samples taken during the growing season will then reveal what nutrients are needed to stimulate regrowth.
McCourt believes that older stands, irrigated and cut several times per season, might not be able to fix enough nitrogen to support maximum yields. A few pounds of added N allows plants to put all their resources into regrowth, he says.
Field research by WFS Inland Division Agronomist Dave Barta may support McCourt's view. A 7-10-10 liquid fertilizer was applied through center pivots at 2.5 gallons/acre. Participating growers applied the blend between cuttings in addition to their traditional off-season fertilization regimes.
The growers consistently saw a half ton/acre/cutting yield boost, and Barta is convinced some of that gain was due to the nitrogen.
Washington State University extension agent John Kugler, whose specialty is alfalfa production, agrees that N applications are prudent in certain situations.
“Studies show that, when nitrogen fixing is inhibited by disease or soil conditions, alfalfa responds positively to an application of nitrogen,” he says.
Older stands are most likely to be impacted by disease. Kugler warns, however, that fertilizer N is wasted if applied to healthy stands capable of fixing large amounts of the nutrient.
“Research also tells us that, when nitrogen is applied to alfalfa, the plants stop fixing their own,” says Kugler. “Any consideration to apply nitrogen on an alfalfa stand should be balanced against the financial implications of that fact.”