In the early 2000s, we did several trials looking at the nitrogen needs of winter forage — triticale, rye, wheat and barley.
We found that 80 to 100 pounds of N per acre was the optimum economic return for spring nitrogen. Yields were 1.5 to 2.5 tons of dry matter per acre for most sites. We’ve learned how to double our yields since that work was completed.
By planting earlier — 10 days to two weeks before wheat for grain — we increased yields 35%. We also learned that up to 60 pounds of N per acre in the fall increased spring yields 43% on a field without prior spring manure.
The early planting and fall nitrogen availability significantly increased the number of tillers. Thus, it is common for yields to be 3.5 to 4.5 tons of dry matter per acre. Farms have reported more than 5 tons of dry matter per acre on better soils in areas south of New York.
If we want to harvest 20% crude protein to offset the very expensive soymeal prices, the crop needs to be fed. Most well-managed winter forage is shorted on nitrogen and sulfur.
Based on current soymeal and nitrogen prices, if you are putting on 120 pounds of nitrogen and sulfur, it will cost about $60 per acre. If you’re getting 2 tons of dry matter per acre, the protein is worth $208 per acre as soybean meal. A 3.5-times return is not a bad deal.
If you are getting 3 tons per acre and did not apply any fall nitrogen, you would have shorted the crop on yield and protein if you had only put on 120 pounds of N per acre.
If you have manure to get rid of and fertilizer to apply, why not solve both issues at one time?
Keep in mind, though, that topdressing unseparated manure on tall winter forage is a prescription for potential disaster. The manure will stay lodged in the forage crowns, making unfeedable silage the next spring.
Also, you waste a lot of nitrogen through broadcasting — about 120 pounds of N per acre, or about $56 per acre of fertilizer, for every 8,000 gallons of manure that is lost to the air. Manure injection can save a lot of money in fertilizer costs, even though it costs more upfront.
One of my recent articles went into detail on utilizing a wavy coulter manure injection system to meet all the fertilizer needs for winter forage by applying the nitrogen directly into an 8- to 10-inch-tall winter grain sod. We are looking forward to testing another company with a rolling coulter, Zoskes, this spring on a neighboring farm.
Injecting manure after the soil temperature has fallen below 50 degrees F can store the N in the manure as ammonia attached to the soil until spring. It is then converted to nitrate to be used by the winter forage the following spring.
Penn State research has found a 38% reduction in the loss of soluble phosphate using injection. That means the fertilizer is staying on your field or farm to grow crops rather than polluting waterways.
The only downside is that for winter forage that matures early, the manure nitrogen may not release normally when it’s cold in late spring, as we experienced in 2018.
I have little worry about leftover manure nitrogen after winter forage harvest as most farms are strip-tilling corn into the stubble immediately afterward. In fact, where we shorted the winter forage on nitrogen, the crop scours the soil, leaving insufficient nitrogen for the corn to start with. In those cases, pop-up nitrogen sources were needed for rapid early corn growth.
Using the same rolling coulter unit to inject manure into winter forage stubble where the corn row will be eliminates that problem. As for cool-season, intensively managed grass fields, any nitrogen not available to the first cutting will be available for the second cutting. Thus, injection is environmentally and economically sound.
Applying to cool-season grass
The newest wrinkle on this, developed by Dale Dewing and Paul Cerosaletti of Delaware County Extension, is to do the exact same thing we described above for winter forage, but apply it to intensively managed cool-season grasses.
Applying manure to the living sod in late fall to early winter keeps it in the ammonia form. As soon as the grass starts to grow in spring, the ammonia converts to nitrate and is released to support the crop yield and protein. You can meet all the nitrogen and sulfur needs for top yield and quality with the manure.
Even with daily spread, if you uniformly inject liquid manure, you can apply throughout November and most of December to both grass and winter forage. When spreading, where you run out, you stop. Then lift the rig and start again there with the next load.
You are not spreading manure; you are fertilizing the field and crop. The bonus is that manure also has the sulfur that’s critically needed for crude protein. For smooth mowing, the field should be rolled before it freezes solid to push down any lifted sod and stones.
For our trials on winter forage, the injector was on 18-inch centers. Moving closer to 15-inch centers will give much more uniform application and will allow you to come back with alternate units closed for 30-inch-center-injected manure to match the rows of the following corn crop.
The other issue Cerosaletti and Dewing found with injecting in grass is that “we had the coulter at a 6.5% angle, and we are thinking that at our typical rates, we might like the 4-degree better.”
The reasoning is that the shallower angle will lift the sod less and will be less likely to bring up ledge rock that underlies most of the fields while still capturing all the injected manure. While applying into sod on a rainy day, they found less lifting because the sod was more slip from the water.
Optimizing for corn
If you’re not growing winter forage, late fall manure can still be injected with a nitrification inhibitor for spring corn production.
Inject the manure as if you were banding fertilizer under where the corn will be planted — in other words, match row-width passes like you were planting corn. Then, come back in early spring and no-till your corn directly over the manure bands, which can supply most — if not all — of your fertilizer needs.
In a recent trial, 10,000 gallons of manure per acre applied 210 pounds of N (70% as volatile captured ammonia); 114 pounds of phosphorus; and 225 pounds of potassium per acre. This is a lot of fertilizer directly under the plant.
Keep in mind that this strip-till or no-till system is not for fields that have been beat to death with tillage and trucks.
For fields that have winter forage harvested — on days that you can’t make haylage — you can inject manure into the winter forage stubble for corn, again on 30-inch rows.
Research by Quirine Ketterings, professor of animal science at Cornell University, found that injecting up to 15,000 gallons of manure per acre in line with 30-inch corn silage planting could meet all, or nearly all, of the nutrient needs of corn without burning and without additional fertilizer for those specific fields (the maximum economic return in her trial was at 9,000 gallons per acre).
Adding a nitrification inhibitor to the manure before injecting can help hold the nitrogen in a form that will neither leach nor denitrify for six to eight weeks after the soil warms in the spring, or after injection following winter forage harvest.
For corn plants, use this as a rule of thumb: 6 pounds N for the first six weeks, then 6 pounds N per day after that. The nitrification inhibitor will ensure the nitrogen will be there and available when the corn starts its rapid growth phase.
Don’t add an inhibitor to manure fall-injected into winter forage or perennial grasses as we want it to be available as soon as the grass or winter forage greens in the spring.
Savings on fertilizer will pay for the soil tests you haven’t taken, topdressing for your legume hayfields and the lime that has been forgotten for the past five years of poor dairy economics.
Kilcer is a certified crop adviser in Kinderhook, N.Y.