Anhydrous Ammonia Application Gets Delayed

How long should you wait to plant corn after applying anhydrous?

The wet spring has delayed early season anhydrous ammonia application. A common question from farmers is "How soon can I plant corn after applying anhydrous?" Brian Lang, an Iowa State University Extension crop specialist at Decorah in northeast Iowa, provides the following answer.

If you put anhydrous ammonia deep enough into the soil (6 to 8 inches below the surface) you can plant immediately after the application, but you have to be certain about the depth. What you are trying to do is avoid placing the seed in the ammonia saturation zone. This can kill geminating seeds.

As anhydrous ammonia is applied, the liquid form that is injected quickly becomes a gas and expands. The amount of expansion that occurs is a function of soil moisture, and the greater the moisture level the smaller the zone will be. Soil moisture is a function of soil texture, and finer textured soils have greater moisture holding capacities.

You can also apply anhydrous ammonia on a diagonal to avoid application situations that might kill an entire row of corn.

Should you use inoculant on bean seed?

Several farmers have also asked Lang whether he thinks they should use rhizobia inoculants on soybean seed. He offers the following general recommendations for Iowa and other Midwest states.

No inoculants are needed if you are planting beans on silt loam soil 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 pH 6. The seed should be inoculated every year when planted on sandy soils or in fields with no soybean history in the last three to five years.

New recommendations for the more northern Midwest states are that where soils tend to be cooler, the rotations longer and beans are planted in no-till, it may pay to inoculate soybean seed every year.

What about insecticide seed treatments?

Cruiser and Gaucho are systemic (neonicotinoid) insecticides that can be applied to seed before planting. They protect seed during germination against secondary insects like seedcorn maggot, bean leaf beetle and will control soybean aphid for about 60 days after planting date. These products are still being evaluated as to their economic value under various circumstances, says Lang.

For example, they would protect against seedcorn maggot, but at a higher expense than a planter-box treatment, although easier to handle. They protect against early season bean leaf beetle, but in Northeast Iowa these populations are quite variable. Although there is a potentially greater value for this tactic with food grade soybeans, and with the possibility that bean leaf beetle may transmit the bean pod mottle virus and cause some seed discoloration at harvest.

They control soybean aphids (and will also kill beneficial insects) for about 60 days from planting date. But most aphid activity occurs after that point. However, if soybeans had to be replanted in late spring due to hail or flood, for example, then these insecticide seed treatments could be of significantly greater value for controlling aphids into August. Research is continuing on evaluating the value of using these seed treatment insecticide products, notes Lang.

TAGS: Extension
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