Animal manure is often used as a source of crop nutrients. Unfortunate
ly the nutrient content of manure is quite variable, The objectives of
this study were to: (i) evaluate the nutrient content of dairy manure
from different handling systems and determine if published nutrient c
redits are outdated, (ii) determine if the nutrient content could be e
stimated from the solid content of the manure, and (iii) determine the
seasonal variation of the nutrient content of manure. Three dairy-man
ure handling systems, dairy feedlots, dairy barn cleaners, and dairy b
edded packs, were sampled sequentially from June 1990 to April 1992. M
anure was sampled by handling system at 13 farms located in northeaste
rn Iowa. Samples were analyzed for total Kjeldahl N (TKN), ammonium-N,
P2O, K2O, and solid content. The nutrient values found in this study
were higher than values previously reported in Iowa and other midwest
states. For dairy feedlot manure, solid content of the manure was corr
elated with the nutrient content of the manure. A correlation between
solid content and nutrient content was not evident for dairy barn clea
ner manure or dairy bedded pack manure. Dairy feedlot manure nutrient
values were higher in summer and fall than in spring and winter. Seaso
nal variation was not evident for the dairy bedded pack manure or the
dairy barn cleaner manure. The use of manure in a nutrient management
program is dependent on accurate nutrient recommendations based on tho
rough and timely manure sampling.