Abstract
The aim of this study was to assess the effect of a three-year application of digestate from an agricultural biogas plant on the physicochemical properties of highly acidic pHKCl 4.4 ± 0.23, silty loam soils with low macronutrient content and on the yield and nutritional value of switchgrass (Panicum virgatum L.) biomass harvested for green fodder. The experiment included the following treatments: (1) O (control)—no fertilisation, (2) NPK—mineral fertilisation with (in kg ha−1) 150 N, 53.0 P and 105 K, (3) biogas digestate at 30 m3 ha−1 and (4) biogas digestate at 60 m3 ha−1. The higher application rate of biogas digestate significantly reduced soil acidity to pHKCl 4.9 ± 0.18 and improved its sorption properties. It also increased the soil organic matter content from 5.6 ± 0.21 to 6.4 ± 0.22 g Corg kg−1 and of K and Zn. The higher level of biogas digestate significantly increased switchgrass yield to 5.15 ± 0.26 t ha−1. The lower application rate of biogas digestate resulted in forage yield of 4.30 ± 0.20 t ha−1 comparable to that obtained after mineral fertilisation (4.33 ± 0.22 t ha−1). Following application of mineral fertilisers and the higher level of biogas digestate, the number of panicles per plant (150 ± 2.49–157 ± 0.6.17), panicle height (107 ± 1.98–114 ± 2.08), crude ash content (61.2 ± 0.43–65.5 ± 0.38) and protein content (106 ± 0.59–92 ± 1.11) in the switchgrass biomass from the first cut were higher than in the case of unfertilised soil (110 ± 3.81, 93 ± 1.32, 55.5 ± 0.40, 80.3 ± 0.37). The use of mineral fertilisers and biogas digestate increased the content of protein, P and Mg in biomass from the second cut. The results suggest that the use of digestate improved the physicochemical properties of highly acidic soil and increased the yield of switchgrass forage without diminishing its nutritional value.
Highlights
Climate change and increasingly frequent extreme weather events have a significant impact on crop growth and yield
We found no research on the effect of digestate on the forage yield and nutritional value of switchgrass
We found no research on the effect of digestate on the forage yield of switchgrass, but, Tilvikiene et al [47] reported that for long-term fertilisation, the organic matter of digestate may play a significant role in the increase in cocksfoot biomass production
Summary
Climate change and increasingly frequent extreme weather events have a significant impact on crop growth and yield. A reduction in the amount of precipitation or its high irregularity and the resulting rapid rainfall and prolonged droughts, result in reduced yields of plants grown for both consumption and fodder purposes. These negative phenomena are expected to intensify in Europe [1]. This makes it necessary to introduce new crop species, less sensitive to adverse environmental conditions, which can be a good source of feed for farm animals. For more than 70 years it has been widely used in the US on the Great
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