Abstract
Perennial non-food energy crops are currently discussed as a more sustainable alternative to conventional energy crops like maize. As they can be cultivated on marginal soils, they reduce the risk of land use and food vs. fuel conflicts. In this study, we evaluated the perennial energy crop Sida hermaphrodita for its potential to be cultivated on marginal substrate and conventional agricultural soils over a three-year field and mesocosm experiment at agricultural conditions. Furthermore, we aimed for a closed nutrient loop by fertilizing plants with biogas digestate and using the carbon fraction of the digestate as soil amendment to ameliorate the overall soil fertility. As controls, plants were either untreated or fertilized with an equivalent amount of mineral NPK fertilizer. We found S. hermaphrodita to give highest DM yields of up to 28 t ha−1 under favorable soil conditions when fertilized with mineral NPK. However, on marginal substrate digestate fertilization resulted in a clear biomass yield advantage over NPK fertilization. An increased soil carbon content, water holding capacity and basal soil respiration indicated improved soil fertility in the marginal substrate. These results demonstrate the great potential of S. hermaphrodita to be cultivated on marginal soil in combination with organic fertilization via biogas digestate.
Highlights
Energy crops have the potential to diversify our energy production [1]
Highest DM yields of up to 28 t ha−1 were obtained on rich field soil in the third year of the experiment, when fertilized with mineral NPK (Fig. 2)
In mesocosms, filled with marginal sandy substrate a maximum DM yield of 9 t ha−1 was measured for plants fertilized with digestate in their third year of growth and fertilization (Fig. 2)
Summary
Energy crops have the potential to diversify our energy production [1]. cultivation of species like maize and oilseed rape on productive agricultural soils, causes land use conflicts and negatively impacts food security [2,3]. Compared to other perennial energy crops, S. hermaphrodita has the potential to minimize land use conflicts, as it can be cultivated on light soils and marginal lands [3,6,10,11]. S. hermaphrodita is a forb species from the North American prairies belonging to the Malvaceae family that develops a large root system allowing access to water and nutrients even when resources are limited. It grows well on sandy or rocky soils with low organic matter content and produces relatively high biomass yields even with low nutrient levels in the soil [9,13]. We tested S. hermaphrodita for its potential cultivation on both a sandy marginal substrate and a pebbly field soil and compared the yield potential to a conventional rich field soil at agricultural conditions
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