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Energizing marginal soils: Perennial energy crops, Legume intercropping and organic fertilization – Key elements for sustainable biomass production

Moritz Nabel

As a way to avoid land use conflicts, the use of marginal soils for the production of plant biomass can be a sustainable alternative to conventional biomass production (e.g. maize). However, new cropping strategies have to be found that meet the challenge of crop production under marginal soil conditions. We aim for increased soil fertility by the use of the perennial crop Sida hermaphrodita in combination with organic fertilization and legume intercropping to produce substantial biomass yield.

We established a three-year outdoor mesocosm experiment testing the perennial energy crop Sida hermaphrodita grown on a marginal model substrate (sand) with four kinds of fertilization (Digestate broadcast, Digestate Depot, mineral NPK and unfertilized control) in combination with legume intercropping. Further, we established a 1000 m2 field experiment where we test the practical cultivation of the perennial crop Sida hermaphrodita. An additional greenhouse study using Rhizotrons focused on the optimization of organic fertilization on marginal substrate by comparing broadcast application to application in localized nutrient depots in the rhizosphere.

In Mesocosms, biomass yields of Sida were 25% higher when fertilized organically, compared to mineral fertilizer. In general, broadcast digestate application reduced root growth and the wettability of the sandy substrate. However, when digestate was applied locally as depot to the rhizosphere, root growth increased and the wettability of the sandy substrate was preserved. Depot fertilization increased biomass yield by 10% compared to digestate broadcast fertilization.
We intercropped Sida with various legumes (Trifolium repens, Trifolium pratense, Melilotus spp. and Medicago sativa) to enable biological nitrogen fixation and make the cropping system independent from synthetically produced fertilizers. We could show that Medicago sativa grown on marginal substrate fixed large amounts of N, especially when fertilized organically, whereas mineral fertilization suppressed biological nitrogen fixation.

We conclude that the perennial energy crop Sida in combination with organic fertilization has great potential to increase the soil fertility of marginal substrates and produce substantial biomass yields.

Publications

Nabel, M., Temperton, V. M., Poorter, H., Lücke, A. & Jablonowski, N. D. (2016). Energizing marginal soils – The establishment of the energy crop Sida hermaphrodita as dependent on digestate fertilization, NPK, and legume intercropping. Biomass and Bioenergy, 87, 9-16.

Jablonowski, N. D., Kollmann, T., Nabel, M., Damm, T., et al. (2016). Valorization of Sida (Sida hermaphrodita) biomass for multiple energy purposes. GCB Bioenergy.

Nabel, M., Barbosa, D. B., Horsch, D. & Jablonowski, N. D. (2014). Energy crop (Sida hermaphrodita) fertilization using digestate under marginal soil conditions: A dose-response experiment. Energy Procedia, 59, 127-133.           

Barbosa, D. B. P., Nabel, M. & Jablonowski, N. D. (2014). Biogas-digestate as nutrient source for biomass production of Sida hermaphrodita, Zea mays L. and Medicago sativa L. Energy Procedia, 59, 120-126.


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