Planting Corn After Anhydrous Application

Every year someone asks "how long to wait after anhydrous is applied before a field can be tilled or planted?" Rod Swoboda

Published on: May 4, 2005

How long should you wait after applying anhydrous ammonia before you plant corn? Or before you can do tillage to the field? Brian Lang, Iowa State University Extension crop specialist at Decorah, gives the following answer.

"Regarding tillage, this is not a concern as long as the tillage is more shallow than the anhydrous ammonia is injected," he says.

"However, if the soil is inverted soon after anhydrous is injected, such as with a chisel plow, some volatilization of the ammonia could occur if a zone of concentrated ammonium is exposed at the surface. By waiting at least one day before tilling, the chance for nitrogen loss would be minimized. Having normal soil moisture conditions further minimizes the potential problem, whereas dry soil conditions increase risk."

Regarding when to plant, "There is no specific "wait time" for planting after applying anhydrous ammonia," says Lang. "What is important is that the seed does not come in contact with the ammonia zone. As long as the anhydrous is injected at a proper depth and soil sealing behind the knives is "normal", this is not a problem."

However, sometimes the anhydrous is not being injected as deep as it should, or the soil doesn't seal behind the knife as good as anticipated, points out Lang. "This can bring the ammonia zone closer to the seed zone. An additional "safety factor" often used is to inject the anhydrous at an angle to the way the corn rows will be planted so that if there is a problem, the anhydrous zone won't affect entire rows of corn," he says.

Use rhizobia inoculants on soybeans?

Soybean bacteria inoculants for nitrogen fixation were evaluated in the mid-1990's on 44 no-till trials across eight Midwest states (IA, IL, IN, MI, MN, OH, SD, WI). In the more southern states (IA, IL, IN, OH), inoculation had little effect on yield. But in the more northern states (MI, MN, SD, WI), inoculated soybeans yielded 3.8 bushels per acre more than uninoculated soybeans (8.6% yield increase).

ISU’s Brian Lang notes that the following are general recommendations for use of inoculants in Midwest states:

  • No inoculants are needed on silt loam and loam soils where well-nodulated soybeans have been grown in the last three to five years, and where soil pH has been maintained above 6.
  • Seed should be inoculated every year for fields with no soybean history in the last three to five years.
  • Seed should be inoculated every year when planted on sandy soils, regardless of field history of soybean production.
  • Updated recommendations for the "northern" mid-west states included: consider inoculation where soils tend to be cooler and soybeans are planted using reduce-till and no-till, regardless of field history of soybean production.

Save money on soybean seeding rates

"Recent research by both ISU and major seed companies indicates we can keep seeding rates in the more affordable ranges, lower than we may have been planting in the past," says Clarke McGrath, ISU area crop specialist at Lewis in southwest Iowa. "With the cost of seed, this is timely information."

Harvest stands of 110,000 and above produce similar soybean yields in Iowa. Studies have shown that field stand losses of 15% to 30% are common, depending on planter performance, soil conditions, type (if any) of seed treatment, weather and pest pressure. These field losses are due to lack of seed germination, insect and disease damage, barren plants, lodging, and many other factors. To make it more complex, each field will likely have a different stand loss.

"So, if we shoot the average, if we want to harvest 130,000 plants and we average a 23% stand loss before harvest, the seeding rate should be 159,900 seeds per acre. More of the data and info can be found at