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Sidedressing 'Flowers Can Ease Time Pressures of a Busy Spring

Friday, March 1, 1996
filed under: Fertility

He’s a stickler for timeliness; but Lawrence Peterson wasn’t getting much cooperation in that regard during the spring of 1995. A cool, wet spring in his area of southeastern North Dakota, coupled with an unanticipated stay in the hospital, put added pressure on an already-hectic spring schedule. Peterson, who farms approximately 2,000 acres of wheat, sunflower and _____ with the help of one part-time employee, had not been able to apply fertilizer on his upcoming sunflower ground the previous fall; and now Mother Nature’s narrow North Dakota planting window was closing in.

That’s precisely the type of situation where sidedressing nitrogen on the ’flower crop makes good management sense, according to the LaMoure County producer. Peterson, who has grown sunflower for nearly 25 years, says his top priority is timely planting. He prefers to begin seeding his 700-800 acres of sunflower around May 23-24 and be done no later than June 1. In some years, like 1995, that means planting first and then satisfying the crop’s nitrogen needs afterward with a sidedress application. “I’d rather get my ’flowers in on time and put down anhy-drous later if I have to,” he states.

Peterson’s standard sunflower yield goal is 2,000 pounds per acre. To achieve that, he wants to ensure a good 110-120 pounds of available N for the crop. Following wheat, it’s common for his springtime soil test to read 40 to 60 pounds of nitrogen in the top ___ feet; so that translates into his applying 60 to 70 pounds of NH3 preplant or — as in 1995 — via a sidedress treatment.

What’s the proper timing for that side-dressed N? To avoid root injury, it has to be before the sunflower roots have extended too far into row middles. But as Dave Franzen points out, sometimes there’s a tendency to wait a bit too long before sidedressing. One need not hold off until the sunflower is several inches tall before pulling back into the field.

“If sunflower was the last crop being planted, a person could, if he wanted to, turn around, hook up the applicator and sidedress ‘blind,’ ” notes the North Dakota State University extension soils specialist. “From the minute the seed is put in the ground until the plants are too tall to get the applicator through . . . , that’s the sidedress window. It doesn’t start when the crop is six or eight inches tall.”

Another reason not to wait too long is the possibility of being caught by extended wet weather. “There’s usually a period of time — maybe two, three weeks or so for most row crops — where their growth is pretty slow, their root systems are getting established and it’s not all that warm out,” Franzen remarks. “Then, all of a sudden, you receive some rain showers followed by warmer temperatures — and the crop really takes off.” Continued or intermittent rainfall during this period can keep growers out of the field and perhaps shut the door on the sidedress treatment window, the NDSU specialist observes.

Though most sidedressed nitrogen on sunflower goes on in the form of anhydrous ammonia, Franzen says there’s no reason a liquid or granular treatment would not work as well. It depends, he points out, upon the relative price of the various formulations — as well as, of course, on the equipment of the farmer and/or his local fertilizer dealer. Sidedressing while cultivating is an efficient method, but many producers are not set up with that capability.

Sidedressing can be a good way for the sunflower grower to spread out his workload, Franzen summarizes — especially if uncooperative spring weather has delayed fieldwork and planting. “There’s nothing wrong with sidedressing,” he states. “You don’t have to tromp the ground up trying to get your fertilizer on [before planting]. Plus, you get your crop in on a more-timely basis and then go back and put on the nitrogen.”

What’s really counts, emphasize both Dave Franzen and Lawrence Peterson, is having sufficient available nitrogen in place when the crop needs it. If Mother Nature has cranked up the pressure in an already-busy spring, sidedressing those ’flowers could provide some relief from that particular headache.
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