The nitrogen contained in carbonized poultry litter is not plant available

Pyrolysis of biomass, reduces its volume, mass, odour, and potential pathogens, while concentrating nutrients in the resulting biochar. However, the plant availability of nutrients in particular of nitrogen remains largely unknown. Therefore, we investigated the nutrient availability of carbonized poultry litter. A nutrient poor soil was either fertilized with poultry litter or poultry litter carbonized at 500 degrees C at the rates of 1.5, 3 and 6 t/ha. These organic amendments were compared with corresponding rates of mineral fertilizers (NH4 NO3, KCl, CaHPO4, MgSO4) in a pot experiment. After four successive harvests of ryegrass (Lolium sp.) in a greenhouse we analyzed plant nutrient uptake and nutrient concentrations in the soil. While all treatments showed a linear increase in plant growth and nitrogen uptake, the plants fertilized with carbonized poultry litter did not show such a response. The carbonized poultry litter treatment produced more biomass than the unfertilized control, but the tissue concentration of nitrogen was below that of the control. Mehlich 1 extractable nutrients in the soil showed that there is more available phosphorus, potassium, calcium and magnesium in the soil fertilized with the carbonized poultry manure, but these available nutrients were not utilized due to the nitrogen limitation to plant growth. The results clearly show that nitrogen contained in carbonized poultry litter is not available for plants.