Farm Table says:
The anaerobic digestion of biomass such as energy crops, organic residues and animal wastes for biogas production is considered as one of the most efficient ways of renewable energy production. In the Czech Republic, rather massive development in the implementation of biogas stations has been recorded in the last three years. Along with the growing number of biogas stations, there is an increased production of digestate as a by-product of the biogas production.
This study compares the effect of the application of digestate, straw, cattle slurry and inorganic fertilizers on crop yield and soil organic matter content.
Evaluated in soil from the field experiment in PragueRuzyně (Orthic Luvisol, clay loam) with winter wheat:
• Total organic carbon (C),
• Total organic nitrogen (N),
• Hot water soluble C,
• Microbial biomass C
• Hydrophobic soil components
All fertilized treatments significantly increased grain yield above the level of non-fertilized control (5.68 t/ha), and the sequence was as follows: digestate (9.88 t/ha) > NPK (9.80 t/ha) > cattle slurry (9.73 t/ha) > digestate + straw (9.35 t/ha). Average organic C content in the soil ranged from 1.668–1.704% and the effect of different fertilization was not significant.
The highest increase of microbial biomass C was recorded in digestate + straw (43.2% increase compared to control). Highly significant correlations were found between hydrophobic soil components and hot water soluble C (r = 0.988; P ≥ 0.05) and microbial biomass C (r = 0.964; P ≥ 0.05). Total organic N content ranged from 0.157–0.160% and differences among treatments were insignificant.
The results obtained in this field experiment indicate that digestate with the density of the liquid phase (dry weight 6.2%) and N content (6.1% in dry weight) is close to cattle slurry (dry weight 7%, N content in dry weight 4.8%) but it is rather similar to mineral N fertilizer by form of the contained nitrogen and rate of N utilization by plant. Fertilization with digestate brings an effect on crop yields increase but does not improve significantly the level of organic matter in the soil, so in longer-term it is necessary to add organic matter from other sources.