Nitrogen Availability from Poultry Litter and Pelletized Organic Amendments for Organic Rice Production

Published in Agron. J. 103:1284–1291 (2011) Posted online 9 Jun 2011 doi:10.2134/agronj2011.0005 Copyright © 2011 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. 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. O rice is produced on 20,000 ha in the United States, and California is the single largest producer with 9400 ha (USDA-Economic Research Service, 2008), most of which is grown in the Sacramento Valley. In this region N fertilizer has traditionally been applied as poultry litter, because cover crops do not grow well on the heavy textured, high clay soils of the Sacramento Valley. While poultry litter is relatively cheap, its low N concentration and bulk density can lead to high transport costs per unit N (Hadas et al., 1983). Furthermore, poultry litter is challenging to manage due to inconsistent nutrient content and release (Sims, 1986; Rees et al., 1993; Chadwick et al., 2000), Also, due to its relatively high P content, continued applications of poultry litter to meet an N requirement can lead to high soil P contents (Linquist et al., 2010) and the possibility of off -site contamination (Pote et al., 1996; Golden et al., 2006). Finally, key changes in the poultry industry including increased regulation of unprocessed organic wastes, a shift toward in-house pelletization by major producers, and an increase in the use of sterilants and absorbents in poultry houses necessitating less-frequent litter renewal, have recently led to decreased availability of poultry litter for the organic production market, even as demand for this N-source has grown (L. Benson, personal communication, 2008). Collectively, these factors have resulted in organic growers searching for alternative sources of organic N. One strategy to combat the disadvantages of using poultry litter in fi eld-scale production is to isolate the fi ne fraction and pelletize it (Ndegwa et al., 1991). Pelletizing poultry litter increases bulk density and particle size uniformity (McMullen et al., 2005) and concentrates nutrients, resulting in a more rapidly mineralizable form of N (Hadas et al., 1983). Lopez-Mosquera et al. (2008) found that pelletized poultry litter had more stable nutrient characteristics, no fecal bacteria, no odor, and was easier to transport, store and apply in the fi eld than fresh poultry litter. Studies comparing fresh and pelletized poultry litter have found that similar amounts of N are mineralized (Hadas et al., 1983; Cabrera et al., 1993) and plant N uptake and yield are similar regardless of litter form (Golden et al., 2006). In addition to poultry litter, blood meal, meat meal, and feather meal have been commercially pelletized and are being used as fertilizer for horticultural crops (Gaskell and Smith, 2007); however they have not been evaluated in rice production systems. In all crop production systems improved synchronicity between N supply and crop N demand can lead to increased N use effi ciency; however synchronicity may be more diffi cult to achieve with organic fertilizer N sources due to variable N mineralization rates (Sims, 1986; Dahlin et al., 2005). Golden et al. (2006) reported that asynchronicity of N supply with plant N demand results in low nitrogen recovery effi ciency (NRE) of poultry litter-N (14%) and concluded that maximum grain yields could only be achieved with prohibitively high rates (270 kg N ha–1) of poultry litter. In contrast, poultry manure NRE in rice systems in India showed 33 to 37% of N applied as poultry manure being recovered each season, and was similar to the NRE of urea (28–43%) at that fi eld site (Bijay-Singh et al., 1997). Th ese discrepancies may be attributable to ABSTRACT Nitrogen is the most limiting nutrient in irrigated rice (Oryza sativa L.) production, and growers continue to be faced with the challenge of meeting crop N demand, particularly in organic production systems. Th e main objective of this study was to determine how rice yield was aff ected by seasonal availability of N from organic sources under continuously and noncontinuously fl ooded conditions. Laboratory and fi eld experiments were conducted to determine the eff ectiveness of the commonly used poultry litter, pelletized organic fertilizers (blood, meat, and feather meal 13–0–0, feather meal 12–0–0, poultry litter plus feather meal 6–3–2), and (NH4)2SO4, in synchronizing the supply of mineralized N with the demand of N by rice. Th e N mineralization of all organic fertilizers occurred primarily during the fi rst 53 d aft er planting, results which were confi rmed subsequently in a laboratory incubation study. In all fi elds, fertilizers increased grain yield and N uptake relative to a zero N control. Relative to poultry litter, the pelletized fertilizers resulted in higher yields (9980 vs. 9267 kg ha–1), N uptake (140 vs. 114 kg ha–1), and N recovery effi ciency (35 vs. 20%) in all fi elds. It was concluded that pelletized fertilizers were signifi cantly more eff ective than poultry litter in supplying N to the crop when fi elds were continuously fl ooded. In contrast all organic fertilizers were less eff ective in supplying N when fi elds were drained for weed control due to lower N recovery effi ciency (26%) and N loss through denitrifi cation, indicating that organic fertilizer application may not be economically viable under such circumstances.