March 15, 2013 – Research on applying liquid livestock manure as a spring top-dress fertilizer to wheat has been ongoing in Ohio for several years. There is usually a window of time, typically around the last week of March or first week of April, when wheat fields are growing and firm enough to support manure application equipment. The key to applying the correct amount of manure to fertilize wheat is to know the manure’s nitrogen content. Most manure tests reveal total nitrogen, ammonia nitrogen and organic nitrogen amounts. The ammonia nitrogen portion is readily available for plant growth. The organic nitrogen portion takes considerably longer to mineralize and generally will not be available when wheat uptakes the majority of its nitrogen in the months of April and May. Some manure tests also list a “first year availability” nitrogen amount. This number is basically the ammonia nitrogen portion of the manure plus about half the organic nitrogen portion. Again, for the purpose of fertilizing wheat, the organic portion of the nitrogen should not be considered available in time to impact yields. Most deep-pit swine finishing manure will contain between 35 and 45 pounds of ammonia nitrogen per 1,000 gallons. Finishing buildings with bowl waters and other water conservation systems can result in nitrogen amounts towards the upper end of this range. Finishing buildings with fixed nipple waters and surface water occasionally entering the pit can result in nitrogen amounts towards the lower end of this range. To capture the most nutrients from manure farmers should consider incorporation. Incorporation can result in less nitrogen loss and can especially reduce the loss of dissolved reactive phosphorus. Three years of on-farm wheat top-dress results are summarized in Table 1. Each field trial was replicated four times. In each plot, the manure ammonia nitrogen application rate was similar to the nitrogen amount in the urea fertilizer – typically about 100 pounds per acre. The manure was applied using a 4,800-gallon tanker with a Peecon toolbar 13.5 feet in width. This toolbar cuts the soil surface with a straight coulter and a boot applies the manure over the soil opening. Urea was applied using a standard fertilizer applicator. Table 1. On-farm Swine Fishing Manure Topdressing of Wheat Results (bu/ac) Year Swine manure (surface applied)* Swine manure (incorporated) Urea Date of nutrient application 2009 127.5 125.4 128.2 April 7th 2008 63.1 61.4 62.9 April 3rd 2007 102.2 98.0 96.5 March 28th *Incorporation was performed with a modified Peecan toolbar attached to a 4,800-gallon tanker In addition to the Peecon toolbar, OSU Extension as also conducted manure research on wheat using the both the Veenhuizen toolbar and Aerway toolbar. All toolbars cutting through the soil cause some disruption to the growing wheat but side-by-side yield comparisons with convention surface applied fertilizer have rarely shown any difference in yields. Some Ohio commercial dragline operators are routinely applying livestock manure to wheat each spring. This practice is gaining acceptance as it’s faster and more efficient than manure application with a tanker. The risk of soil compaction is also reduced. Dairy manure has been utilized with on-farm research plots when topdressing wheat. Dairy manure contains far less ammonia nitrogen per 1,000 gallons than swine finishing manure and does not consistently produce wheat yields similar to commercial fertilizer. Research on dairy manure as a top-dress to wheat is ongoing and adding 28 percent UAN to the dairy manure to increase its fertilizer value has produced wheat yields similar to commercial nitrogen. When applying livestock manure to wheat it’s recommended to follow the NRCS #633 Waste Utilization Standard to minimize potential environmental impacts. Additional on-farm manure top-dress of wheat plot results can be obtained by clicking on the on-farm research link on the OSU Extension Agronomics Crops team website.