Effects of anaerobic digestion on digestate nutrient availability and crop growth: A review

Anaerobic digestion (AD) changes the composition of the original feedstock, altering factors such as ammonium levels, pH, and the carbon-to-nitrogen ratio, which influence how plants access nutrients after field application. Although AD increases ammonium-nitrogen in slurries, it does not automatically lead to better nitrogen uptake or greater fertilizer savings. When crop residues or cover crops are digested, farms gain more mobile organic fertilizers, allowing more precise nitrogen application when and where crops need it. AD of dairy manure may reduce immediately available phosphorus and micronutrients, though this does not seem to limit short-term crop uptake—yet more research is still required to fully understand these effects.