ARS | Publication request: ESTIMATING SECOND-AND THIRD-YEAR N AVAILABILITY FROM DAIRY MANURE

Submitted to: Wisconsin Fertilizer Aglime and Pest Management Conference
Publication Type: Proceedings
Publication Acceptance Date: January 17, 2002
Publication Date: N/A

Technical Abstract: An increased knowledge of the nitrogen value of dairy manure is needed to increase its value as a fertilizer and to avoid excess nutrient loss to the environment. Since manure is commonly applied to the same fields year after year, it is important to understand the cumulative effects of these multiple year applications. Not only do producers and advisors need to understand first-year nutrient availability and losses, they also need to recognize and account for residual effects. The specific objective of our current work is to estimate residual nitrogen availability from single and multiple manure applications and to determine reliable methodologies to make these estimates. This study emphasizes that field measurement of nutrient availability from manure is difficult and results are highly variable. Using 15N as a tracer greatly reduces this variability. Although there are clear residual benefits from manure applications, the amount of nutrients available is likely more than the 25-30% sometimes measured by other techniques. The conservative credits currently being used in Wisconsin of 30, 10, and 5% for years 1 through 3 for dairy manure will rarely over estimate the actual available amount present. Producers and advisors can be comfortable that at a minimum these amounts will be available.