Short-term N availability in response to dissolved-organic-carbon from poultry manure, alone or in combination with cellulose

Short-term changes in N availability in a sandy soil in response to the dissolved organic carbon (DOC) from a poultry manure (application rate equivalent to approximately 250 kg N ha(-1)) were evaluated in a 44-day aerobic incubation experiment. The treatments included poultry manure alone and two treatments in which an extra source of C, of low water solubility, was added with the poultry manure in the form of a low (1.05 g kg(-1)) and a high (4.22 g kg(-1)) amount of cellulose. All treatments were fertilised with the equivalent of 60 kg N ha(-1) of ((NH4)-N-15)(2)SO4 in solution. A control treatment consisted of sieved field-moist soil plus 60 kg N ha(-1) of ((NH4)-N-15)(2)SO4 in solution. Measurements were made of N2O and CO2 emissions, inorganic NI DOG, biomass N, biomass C and labelled N contained in the inorganic N and biomass N pools. The dynamics of N turnover in this study were driven mainly by processes of mineralisation-immobilisation with little significant loss of N by volatilisation or denitrification. The DOC supplied with the poultry manure played a more important role in N2O emissions than differences in C/N ratio. Changes in DOC and cumulative CO2-C production during the first 11 days were also highly correlated (R-2 = 0.88-0.66, P < 0.01). An initial net immobilisation of N, with significant increases in biomass C and biomass N (P < 0.05) for all treatments over the control at day 11,indicated a high availability of C from the DOC fraction. The presence of additional C from the applied cellulose did not enable a massive N immobilisation. Total inorganic N and unlabelled inorganic N concentrations were highest in soils treated with poultry manure alone (P < 0.05), indicating that an active gross mineralisation of the added poultry manure and a possible positive priming effect were taking place during the incubation.