Biofertilisation with Anaerobic Digestates: Effects on the Productive Traits of Ryegrass and Soil Nutrients

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This study investigated how repeated applications of different types of anaerobic digestates and undigested cattle slurry affected the growth responses and nutritional aspects of ryegrass swards (Lolium perenne L.) and soil nutrient concentrations, in a two-season field trial. The treatments included four different types of anaerobic digestate, undigested cattle slurry, nitrogen control (N-control) with calcium ammonium nitrate (CAN) and a no fertiliser control, distributed in a randomised block design with three replicates. The different types of biofertilisers drove a comparable average forage daily growth rate varying between 65 and 79 kg ha???1 day???1 (p???>???0.05). Crude protein and neutral or acid detergent fibre of the forage were not influenced by any type of biofertiliser (p???>???0.05). Most of the anaerobic digestates led to increases in the level of soil available P and K (p???<???0.05). Despite the detectable influence of the levels of NPK in the biofertilisers on the plant growth responses, different anaerobic digestates when applied using the same dry matter amounts can drive comparable forage grass growth responses with low influence over the nutritional quality of the ryegrass forage. Repeated applications of anaerobic digestates can help to increase or reduce the losses of the soil available P and K. The application of anaerobic digestate, cattle slurry and calcium ammonium nitrate led to increases in the N content of the soil; however, there were no differences between them, despite their considerable differences in terms of N inputs. This might be linked to the volatility and losses of the readily available N from the biofertilisers applied.