Swine (Sus scrofa) manure is an important source of N for crop production. The processing of manure in an anaerobic digester for biogas production is only a partial manure treatment process and is not designed as a disposal method. However, digestion will alter manure characteristics, and this may affect nutrient availability to crops. The objective of this study was to evaluate the N supply to corn (Zea mays L.) from swine manure before and after anaerobic digestion for biogas production. Raw and digested swine manure were late-fall applied as main plots, with three manure N rates as subplots, and six fertilizer N rates as sub-subplots. Response to manure and fertilizer N was determined through soil inorganic N, plant N status and uptake, and grain yield. After 3 yr of study, results indicated no difference between raw and digested swine manure as a source of N for plant use in the year of application or in the residual year. Equivalence to fertilizer N was the same with both raw and digested swine manure, and varied between years with 100% in 2000, 44% in 2001, and 60% in 2002. These differences are attributed to varying growing seasons and N loss potential from time of late fall manure application compared with the spring-applied fertilizer N. Late fall and early spring soil sampling indicated rapid conversion to NO 3 with both sources. Results of this work indicate that digested liquid swine manure can readily supply plant-available N and management for corn production should be the same as with raw swine manure.

Processing of swine (Sus scrofa domestica) manure in an anaerobic Due to a potential increase in the use of anaerobic digester for biogas production is not a complete waste treatment process. Therefore, digested manure must be utilized in some manner, digestion systems for energy production, there is need most likely as a source of plant nutrients. The objective of this study for a reliable estimate of plant-available N and P in diwas to compare the effect of raw and digested liquid swine manure gested swine manure. Evaluation of digested manure as application on soil test P (STP) and inorganic N. A laboratory incubaa crop nutrient source requires determination of the eftion study was conducted for 112 d, with a factorial combination of fects of digestion on nutrient content and the ability to raw manure, digested manure, and inorganic fertilizer at five nutrient provide plant-available nutrients when the material is rates (0, 12.5, 25, 37.5, and 50 mg total P kg Ϫ1 and 0, 50, 100, 150, applied to land. and 200 mg total N kg Ϫ1). Raw and digested swine manure produced Nutrient release from manure at a time when crops the same NH 4-N disappearance, NO 3-N formation, net inorganic N, are not actively assimilating nutrients can cause low nuand increase in STP. Routine STP methods estimated similar P recovtrient use and poor crop response. Binder et al. (1996) ery with both manure sources, averaging 21% at the end of incubation. For the first 28 d of incubation, the STP levels were higher for fertilizer state the importance of synchronizing manure nutrient than manure; STP levels were similar for all P sources after 28 d. mineralization with crop use. Also, environmental loss Nitrification of manure NH 4 was rapid, reaching background concenof nutrients can occur when supply exceeds crop detrations by 14 d, with conversion rate similar to fertilizer NH 4-N. By mand. One problem in manure management is the unthe end of incubation, maximum net extractable inorganic N, precertainty of organic matter mineralization rate. Specific dominantly NO 3-N, averaged 20% less than total applied N for both animal digestion processes (monogastric or ruminant), raw and digested manure. Anaerobic digestion did not substantially feed preferences, and rations of different species and affect manure nutrient supply, and we conclude that anaerobically overall handling of the manure are responsible for difdigested liquid swine manure can provide similar plant-available N ferences in manure nutrient concentrations and effects and P as expected from raw swine manure.

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