CO sub(2) evolution and N mineralization after biogas slurry application in the field and its yield effects on spring barley

• Published in: Applied soil ecology : a section of Agriculture, ecosystems & environment ecosystems & environment, 2009-07, Vol.42 (3), p.297-302
• Main Authors: Terhoeven-Urselmans, Thomas, Scheller, Edwin, Raubuch, Markus, Ludwig, Bernard, Joergensen, Rainer Georg
• Format: Article
• Language: English
• Subjects: Hordeum vulgare
• ISSN: 0929-1393
• DOI: 10.1016/j.apsoil.2009.05.012

The objective of this study was to investigate the effects of biogas slurry derived from straw-rich farmyard manure on the soil microbial biomass, on the mineralization in the field and on the related crop yield. The experiment was carried out in the following four treatments: (1) fallow, (2) fallow + biogas slurry, (3) spring barley, and (4) spring barley + biogas slurry. The CO sub(2) evolution rate ranged between 15 and 120 mg C m super(-2) h super(-1) in both fallow treatments and showed a significant exponential relationship with the soil temperature at 5 cm depth. According to the extrapolation of the CO sub(2) evolution rates into amounts per hectare, approximately 200 kg C ha super(-1) or 27% of the biogas slurry derived C were mineralized to CO sub(2) during a 50 days' period to 18 June in the fallow treatment with biogas slurry. An additional amount of up to 29.5 kg inorganic N ha super(-1) could be calculated as the sum of NH sub(4)-N already present in biogas slurry at the time of amendment and from the amount of biogas slurry mineralized in the soil to NO sub(3)-N. A good agreement between measured and modelled stocks of inorganic N at 0-60 cm depth was obtained after having five-fold increased soil organic C turnover compared to the default values of the model DNDC. The mineralization data are in line with an amount of up to 21 kg ha super(-1) more N transferred by the barley plants to their aboveground biomass in biogas slurry treatment. The N not accounted for by the aboveground plant biomass could be explained by the belowground plant-derived N. CO sub(2) evolution from the soil surface, inorganic N content at 0-60 cm depth and N transfer into barley aboveground biomass lead apparently to similar results after the application of biogas slurry. The soil ATP content after harvest of the barley was significantly larger in the two treatments with biogas slurry, especially in the fallow treatment indicating a positive effect on the soil microbial community.