Dairy Manure Type , Application Rate , and Frequency

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. U nder current dairy feeding practices, only 20 to 30% of the CP fed to dairy cows is secreted in milk. On average, a dairy cow annually produces 8200 kg of milk and excretes 21,000 kg of manure, which contains about 110 kg N (Van Horn et al., 1996). The type and amount of CP fed to dairy cows can have a large impact on total manure N excretion and the proportion of manure N that is excreted in feces and urine (Castillo et al., 2000; Broderick, 2003; Wattiaux and Karg, 2004), how much manure N is lost as NH 3 (Misselbrook et al., 2005), and manure N miner-alization in soils and crop N uptake (Powell et al., 2006). In the Northeast and Midwest regions of the USA, many dairy farmers are increasing the number of cows they milk and importing more feed. This increases the manure amount per unit cropland area. Manure is often applied year after year on land closest to barns (Powell et al., 2007) because transportation costs to spread manure on distant fi elds are higher than the perceived fertilizer value of the manure (Nowak et al., 1997; Saam et al., 2005). While the application of manure to agricultural land recycles plant-available nutrients and organic matter, which can improve crop production and soil quality, repeated manure application in excess of crop requirement may also have adverse effects on the feeding value of forages and soil quality, and increase the risks of To protect the environment, many states regulate when, where, and how much manure can be land applied. Unless targeted for P-based management, agro-nomic recommendations for manure application rates are based on the N requirement of the following crop. Soil-manure incubations and greenhouse trials revealed that single applications of dairy manure derived from cows fed various diets had differential impacts on soil N mineralization, crop yield, and N uptake (Powell et al., 2006) and NH 3 –N losses from land-applied manure (Misselbrook et al., 2005). Recent fi eld studies in central Wisconsin (Cusick et al., 2006) revealed that single and …