title: Co-digestion of animal slurry can increase short-term nitrogen recovery by crops.
abstract: Co-digestion changes slurry characteristics and is supposed to increase short-term nitrogen (N) uptake by crops after application. A higher N uptake from slurry reduces the need for additional mineral N fertilizer. If farmers apply co-digested slurry (CS), a higher N recovery has to be taken into account to prevent losses to the environment. Since data on the effects of co-digestion on N recovery by crops are scarce, a pot experiment was performed. The apparent N recovery (ANR) of five different co-digested pig slurries was compared with their raw source slurries (RS) during 105 d after a single fertilization of ryegrass (Lolium perenne L.), grown under controlled conditions. Slurry was mixed with sandy soil and grass was cut every 35 d. The results show that co-digestion increased (p < 0.05) the ANR at first cut on average from 39 to 50%, at second cut from 7 to 9% (p < 0.05), and had no effect on ANR at third cut (3%). The ANR increase at first cut was likely due to an increase of the NH(4)-N/total N ratio along with a decrease of the organic C/total N ratio of slurry during co-digestion. Field application may under certain circumstances decrease N fertilizer value of CS, due to a higher NH(3) emission compared to RS. A potential ANR increase may then be reduced, absent, or even become a decrease. Under comparable NH(3) emissions, however, CS can in the short term be more valuable as an N fertilizer than RS, and fertilizer savings can likely be realized.
authors.affiliation: Animal Production Div. of the Animal Sciences Group of Wageningen UR, P.O. Box 65, NL-8200 AB Lelystad, The Netherlands. Herman.deBoer@wur.nl
authors.forename: H C
authors.initials: HC
authors.lastname: de Boer
mesh_terms: D000818:Animals; D018556:Crops, Agricultural / Q000378:metabolism*; D005308:Fertilizers; D005525:Food-Processing Industry; D008372:Manure; D009584:Nitrogen / Q000378:metabolism*; D013213:Starch; D013552:Swine; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water; D015003:Yeasts
chemical_list: D005308:Fertilizers; D008372:Manure; D014867:Water; D013213:Starch; D009584:Nitrogen