Circulation of plant nutrients in bioenergy production

Abstract

. In order to achieve the goals, set within the EU Green Course, it is necessary to increase the share of renewable resources, as well as to change the resource use habits, including greater emphasis on the re-use of plant nutrients. Taking into consideration political objectives, it can be expected that energy production from plant biomass obtained from agricultural land will increase in the near future. Perennial grasses are more perspective for bioenergy production in temperate climate conditions, taking into account their growing conditions, productivity, biomass quality, and productive longevity. In order to facilitate the achievement of these objectives, a research was carried out to study the possibilities of the cultivation of reed canary grass (RCG) ( Phalaris arundinacea L.) and festulolium (× Festulolium ) by using the waste products from bioenergy production – biogas fermentation digestate and wood ash – as fertilisers. A field experiment was set up where an equivalent amount of plant nutrients (100 N; 80 P 2 O 5 ; 160 K 2 O, kg·ha -1 ) by different fertilisers was provided, compensating for the missing elements with mineral fertilisers. Two mowing regimes for grass harvesting were used: two-cut and one-cut. The results obtained showed that in this way, partial re-use of plant nutrients can be ensured: waste products provided a significant increase in grass dry matter yield (DMY) for both species. Furthermore, harvest analyses showed that when mowing at plant senescence, part of nutrients had already been transformed from the above-ground parts to the roots, ensuring plant nutrient re-use in the following seasons. Nutrient removal by yield using the two-cut mowing regime, especially for RCG, was significantly higher, compared to the one-cut regime. The highest removal was obtained for potassium: in the two-cut mowing regime, the removal with RCG was two times higher (202.3 kg·ha -1 K 2 O) compared with the one-cut regime (92.5 kg·ha -1 K 2 O). Similar tendencies were observed also for nitrogen and phosphorus, showing the ability of grasses to efficiently transfer the plant nutrients from aboveground biomass to roots during plant senescence, especially for RCG.