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EVALUATION OF DAIRY MANURE NITROGEN‐15 ENRICHMENT METHODS ON SHORT‐TERM CROP AND SOIL NITROGEN BUDGETS
Author(s) -
Powell J. Mark,
Kelling Keith A.,
Muñoz Gabriela R.,
Cusick Paul R.
Publication year - 2005
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2005.0333
Subject(s) - manure , agronomy , loam , forage , crop , manure management , urea , nitrogen , soil water , chemistry , feces , zoology , environmental science , biology , ecology , organic chemistry , soil science
Indirect estimates of manure N availability to crops are highly variable. We developed two methods that label dairy manure N components with the stable isotope 15 N for direct measurement of manure N availability to crops. The forage method involved the labeling then feeding of 15 N‐enriched forage to dairy cows ( Bos taurus ) to label urine N, fecal endogenous N, and fecal undigested feed N. The urea method involved the direct feeding of 15 N‐enriched urea to label urine N and fecal endogenous N. Manure from each enrichment method was applied to a Plano silt loam (fine‐silty, mixed, mesic, Typic Argiudolls) using field plots in 1999 and 2000; corn ( Zea mays L.) was grown for 2 yr after each application. No significant differences were observed in manure 15 N recoveries in corn, soil inorganic N, or soil total N due to manure application year or manure enrichment method. Corn took up 14 to 16% of manure 15 N the first year and 4 to 8% the second year after application. Most 15 N recovery in soil inorganic and total N was found in the upper 30 cm of soil, indicating little downward movement of applied manure 15 N. On average, 68% of applied manure 15 N was accounted for, either in crop uptake (21%) or in the soil (47%). The less laborious and less costly urea enrichment method may be adequate for short‐term (2 yr or less, the range of this study) manure–soil–crop–N cycling studies. Longer‐term studies may need to include fecal undigested feed 15 N derived from the forage enrichment method.