Effect of Biogas Digestate and Mineral Fertilisation on the Soil Properties and Yield and Nutritional Value of Switchgrass Forage

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.

Soil Fertility Management for Better Crop Production

“…Głowacka et al [29] reported significantly increased soil pH, organic matter, cation exchange capacity, and switchgrass yield with application of biogas digestate applied with recommended nutrients. These results suggest that recycling waste organic materials improves soil physicochemical properties to enhance nutrient availability and crop productivity.…”

The effects of inflow of agricultural biogas digestate on bivalves’ behavior

“…The analyzed digestate was characterized by the content of 3.73 kg Mg -1 , and that to maintain below 170 kg N‧ha -1 , a maximum of about 45 Mg digestate per hectare can be used. However, it should be noted that there may be cases when the nitrogen content is lower, e.g., 2.0, in the research by Głowacka et al ( 2020 ) and higher in Drosg et al ( 2015 ).…”

“…The analyzed digestate was characterized by the content of 3.73 kg Mg -1 , and that to maintain below 170 kg N ha -1 , a maximum of about 45 Mg digestate per hectare can be used. However, it should be noted that there may be cases when the nitrogen content is lower, e.g., 2.0, in the research by Głowacka et al (2020) and higher in Drosg et al (2015). Chemical analyses of water during the experiment proved a decrease in nutrient concentration as total forms of phosphorus and nitrogen, and parts of which the bivalves retained as they feed on digestate organic matter (Newell et al 2002(Newell et al , 2005.…”

Energetic Balance of Biogas and Fertilizing Potential of Digestate from Anaerobic Digestion of Manihot Utilissima

“…We noticed that the C/N ratio of Leaves digestates has fallen to 5. The digestate with a C/N ratio of 5 is recognized to be favorable for vegetable crops and fruit trees soils [4,7,58,59]. The C/N ratio of the digestats resulting from the AD of stems was 10.…”

“…It has been shown that one can spread until 30 tons of dry matters of digestate by hectare per year on an acidic poor soil [3,59,60,62]. Therefore, with the 222 10 3 and 1.039 10 6 tons of digestates that we can produce from methanization of 1.55 10 6 tons of stems and leaves of MU, respectively, produced in Kinshasa per year, one could fertilize 7,400 hectares for stems and 39,966 hectares for leaves (SI5A, SI5B).…”