Monday, November 13, 2006 - 11:15 AM

Including Manure in Cash Grain Rotations in Wisconsin: Results from On-farm Trials.

Amy Cook1, Gregg Sanford2, Joshua Posner2, Janet Hedtcke2, John Hall3, and Jon Baldock4. (1) Univ of Wisconsin-Madison, 1575 Linden Dr, Madison, WI 53706, (2) Univ of Wisconsin-Madison, 1575 Linden Dr, Madison, WI 53706, (3) Michael Fields Agricultural Institute, W2493 County Rd. ES, East Troy, WI 53120, (4) AGSTAT, 6394 Grandview Rd, Verona, WI 53593

One relatively new manure management strategy employed by dairy farmers is to transport and apply manure onto the fields of nearby grain farmers. While this system has advantages to both parties, little of the existing research on manure management has been conducted on grain farms. As part of a larger effort to link grain and livestock farms in southern Wisconsin, 22 on-farm trials were conducted to study the agronomic effects of including manure into cash-grain rotations, and environmental effects including potential nitrate leaching and phosphorus accumulation.  Manure was applied at the rate of approximately 100,000 l/ha or 45 Mg/ha.  Using the Pre-sidedress Soil Nitrate Test to estimate nitrogen availability for the corn crop at the V6 stage, nitrogen fertilizer savings from manure in 2004 and 2005 were, on average, 50 Mg/ha and yields were slightly higher (11,800 Mg/ha vs. 11,400 Mg/ha). Crude protein percentage also increased significantly in the manured treatment (9.7% vs. 9.4%). However, there were environmental concerns: 1) At the sites where manure was spread in the early fall (following wheat harvest), fall soil nitrate levels in the manured plots were significantly higher than in the non-manured plots (170 Mg NO3 per hectare/0.9 m versus 87 Mg NO3/ha/0.9 m); 2) In 2004 following corn harvest, fall soil nitrates were low and equivalent between manured and non-manured plots, while in 2005 fall nitrates were significantly higher in the manured plots, indicating an increased likelihood of fall and winter nitrate leaching; 3) While the input of both phosphorus and potassium was greater on the manured than non-manured plots, there was little increase in soil test phosphorus levels, but greater increases in soil test potassium levels.  With increasing prices of fertilizer, it appears likely that more and more Wisconsin grain farms will begin to include manure in their crop rotation.