The objective of this study was to examine the effect on the dry biomass yield of two
dfferent sorghum hybrids (H1 and H2) under five different N-fertilization levels (0, 70, 140, 210
and 280 kg ha-1
) in a soil which was formed by lacustrine deposits of Karla Lake and is
characterized from the downward movement of calcium carbonate from the surface horizons due
to leaching (Fluventic Xerochrept) during 2017. The results demonstrated a significant effect
(P < 0.05) of fertilization only for one hybrid. Biomass yield ranged from 22.2 to 37.5 t ha−1. For
both hybrids, sorghum accumulated a high amount of biomass in stems. Dry stem/total biomass
ratio was rather constant throughout the different fertilization treatments achieving 81.6 and
77.5% for the first (H1) and the second hybrid (H2), respectively. The second hybrid (H2) had a
higher percentage of leaf biomass (20.1 vs. 13.8%) than the first (H1), but lagged behind in seed
production (2.4 vs. 4.6%). Biomass dry matter partitioning and total dry weight are important
selection criteria for energy crops, due to different gross calorific value and ash content but also
because of the different economic importance they may have e.g. the seed is also used as animal
feed. The above high biomass yields of sorghum, confirming the high potential of this crop,
should be taken into serious consideration regarding land use planning, but further investigation
for the gross calorific value and the ash content is needed as well as biomass characteristics that
are quite important in case to improve the combustion process