Manure was applied at spring greenup and after all three harvests (late May-early June, 30 to 40 days later, and September) in seven treatment combinations, not exceeding 20 tons per acre per application during the growing season.

The recommended rate of nitrogen fertilizer was also included as a treatment. Treatments were applied for five growing seasons. The orchardgrass was harvested three times yearly.

The site was previously an unfertilized grass meadow with no history of manure application. Before treatments were applied, the site had a soil pH of 6.2, soil organic matter of 5.7 percent, soil phosphorus of 2 pounds per acre, and soil potassium of 120 pounds per acre.

The average dry matter orchardgrass yield for the total seasonal manure applications of 20, 30, and 40 tons per acre were 3.1, 3.5, and 4.1 tons per acre, respectively. By the second year of the study, the highest rate of manure application yielded more dry matter orchardgrass than nitrogen fertilization.

There was no significant impact of application timing on total yield, although there was a tendency for lower yields when manure was applied in the fall. Nitrogen fertilizer application resulted in significantly greater forage crude protein concentration compared with manure treatments.

The researchers concluded that from a forage yield and nutritive value standpoint, timing of seasonal manure applications to orchardgrass was not a critical issue.

Source: http://web.extension.illinois.edu/state/newsdetail.cfm?NewsID=17500