At harvest, little difference was observed between hybrids in
total above ground biomass, H31 showed a slightly higher value
respect to H41, 11,750 (±3254) kg d.w. ha
1
and 11,580 (±1361)
kg d.w. ha
1
respectively. H41 was the most productive in terms of
seed yield, 4722 (±829) kg d.w. ha
1
, having a harvest index (HI) of
41%, while H31 showed a lower HI (34%) and yielded 3964 (±943)
kg d.w. ha
1
of grain. These yields are in line with the average
values commonly observed in experimental trials in central Italy
[35]. Even though, recorded yields are more commonly observed in
the inland areas of central Italy, while in the coastal areas yields are
usually lower due to low summer precipitation levels. In fact, 2010
was a particularly wet year, with precipitations occurring also
during the summer period (270 mm of rainfall during June, July and
August).
It is worth mentioning that, in the study area sunflower crop
residues are commonly left on the field and are subsequently
shredded and buried into the soil. In our study, the use of crop
residues for energy production was not considered because of the
important role that residues plays in nutrient recycling and soil
organic matter conservation[36]. On average, crop residues produced in thefield trial were about 7300 kg d.w ha
1