Probably depends on the composition of the manure applied. Need to get it tested to see the fertility content and compare that to your soil analysis and apply accordingly. Might not be able to achieve the desired goal in a single year.
"Manure is a source of many nutrients including: nitrogen, phosphorus, potassium and many others. However, nitrogen is often the main nutrient of concern for most crops. Potassium deficiency is usually quite localized within a field and would not be corrected with common rates of manure. However, some improvement might be expected with high rates above 10 tons per acre".
1) Soil analysis
2) Manure analysis
Both are either site specific ( soils) or source specific ( manure...even manure from the same soecies on the same farm can vary significantly)
I would add to those:
1) Realistic Yield Expectations for the soil type you are on in your climate ( NRCS can help you with this)
2) Specific crop being produced.
As stated elsewhere, soils analysis, which involves pH as a main limiting factor for nutrient availability, gets you into the ballpark of whay is needed. In general, you write in the first and second intended plantings, so the recommendation for amendments like manure project out over two growing crops.
FWIW, soils are analyzed for nutrients and trace minerals OTHER THAN NITROGEN. As volatile as N is presumed to be, the recommendation will be for the entire N need of that cropping identified on the soil test submission form.
I also point you to the RYE, because some soils just do not support certain crops well at all. An example is our poorly-drained Craven/ Lenoir/Bethera in eastern NC. No amount of nutrient will overcome the effects of the soggy condition of the soils, so alfalfa is a waste of money to establish.
When considering a new crop, we look first at hardiness for our zone, second at drainage...neither of these can be feasibly changed. Really good cropland may be worth tilng...not this junk!
Successful nutrient management utilizing manure is part science, part art to me. We are using a very low-nutrient lagoon effluent through irrigation systems for the most part on near-in sprayfields, more potent lagoon sludge via honeywagon for fields beyond our piping reach. Tming each different type of application is key for best priduction purposes.
Extension can provide good guidance on manure utility, and NRCS has specialists in the subject, too.
Kay, have you ever worked with a cover crop "expert" on your NC soils to see if there are others in your area that dealing with the same issues as you? If I'm understanding the whole cover crop theory correctly they are designed to build up our soils quality. Maybe your situation could be similar to a manure application, meaning it requires multiple years of covers to reach the desired result. Doing nothing means you've reached peak production and are satisfied with the results.