Surface applying liquid manure to corn fields can occur any time after the corn is planted until the corn is in the V4 (four true leaves with collars) stage. The manure will not harm the emerging corn when applied after planting. Most commercial manure applicators simply drive across the field at an angle to the planted rows. The more advanced the corn field, the more damage is likely to occur from the applicator tracks.
To use a drag hose, the field must be firm enough to support the manure hose. Spring tilled fields that were worked deeply are generally too soft to support the hose unless they were compacted by heavy rainfall. No-till and cover crop systems, where the field was not deeply tilled in the spring, generally work well.
Five years of university research has shown that surface applying manure can produce corn yields about 20 bushels per acre less than incorporated 28% Urea Ammonium Nitrate (UAN). When incorporated, the manure produced yields about 15 bushels per acre higher than the UAN. University research has also shown that corn yields are reduced by about 50 bushels per acre when flattened with a drag hose at the V5 stage.
It is important to know the nutrient content of manure if a livestock producer is counting on using the nutrients to replace commercial fertilizer. Various swine integrators use different feeding rations so a recent manure analysis is important.
Numerous livestock producers have adapted manure tankers for side-dressing manure into emerged corn by modifying rims and wheels for traveling down corn rows. Even with the soil compaction concern, corn yields from side-dressing with manure are similar to side-dressing with commercial fertilizer. Using a manure tanker also allows the corn to be taller, providing a wider window for manure application.
Source : osu.edu