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Comparison of Estimates of First‐Year Dairy Manure Nitrogen Availability or Recovery Using Nitrogen‐15 and Other Techniques
Author(s) -
Muñoz G. R.,
Kelling K. A.,
Powell J. M.,
Speth P. E.
Publication year - 2004
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2004.7190
Subject(s) - manure , loam , agronomy , environmental science , nutrient , fertilizer , mathematics , nitrogen , cropping , soil water , chemistry , soil science , agriculture , biology , organic chemistry , ecology
Measurements of dairy manure nutrient availability to crops typically show great variability. Approaches that are more accurate are needed to improve manure management and reduce nutrient loss to the environment. In this study, we compared direct ( 15 N recovery) and indirect (difference method [Diff Meth] and fertilizer equivalence [FE] approach) methods of determining first‐year dairy manure N availability or recovery during three cropping seasons. A field experiment was conducted on a Plano silt loam (fine‐silty, mixed, superactive, mesic Typic Argiudolls) planted to corn ( Zea mays L.). Plots received either manure, fertilizer N, or no N. Microplots receiving 15 N‐labeled manure were also established each study year. Manure was applied to a new plot each cropping season. Whole‐plant N uptake was the best crop parameter to use for FE estimates. Estimates of N availability by relative effectiveness (Rel Eff), which are derived from the Diff Meth, and FE were similar (32 and 41%, respectively) and higher than unlabeled N or 15 N recovery measurements because these indices factor in N use efficiency. Measures of the Rel Eff of manure N use were highly affected by control plot N uptake. The FE approach is less influenced by control plots, but it requires the inclusion of several more treatments and use of mathematical functions to describe crop response to N. These limitations are reflected in the wide ranges obtained for N availability estimates (−60 to 148%). Although apparent N recovery by the Diff Meth (14%) or direct measurements of 15 N recovery (16%) were close on average, variability tended to be much lower for the 15 N method. In addition, the Diff Meth was highly dependent on initial soil conditions. Use of 15 N‐labeled manure, although more costly and time‐consuming, provided more consistent and reliable results.