Nitrogen supply to irrigated Sultana grapevines on own roots or on Ramsey
rootstock was varied in a field trial conducted at Irymple, north-western
Victoria, over 3 seasons. The nitrogen treatments imposed were 0, 40 and 80 kg
N/ha.year supplied in 4 equal applications (2 pre-flowering — late
September and mid-October; 1 post-flowering — mid-November; 1
post-harvest — late February) Yields of dried vine fruit were responsive
to both nitrogen supply and rootstock. Despite lower bud fertility, Sultana on
Ramsey rootstock out-yielded Sultana on own roots due to greater numbers of
1-year-old canes suitable as bearers, more berries per bunch and larger
berries. Yield of Sultana on own roots responded in a similar manner to
increasing nitrogen supply as yield of Sultana on Ramsey rootstock. Yield
increases were due to improved bearing potential (more suitable bearers) and
more berries per bunch when nitrogen supply increased from 0 to 40 kg
N/ha.year. When nitrogen supply was raised from 40 to 80 kg N/ha.year,
a further yield increase was due to enhanced bud fertility and larger berries.
These yield components behaved differently for Sultana on own roots compared
with Sultana on Ramsey rootstock, but, overall, balanced out such that final
yield was not affected by rootstock. Consequently, rootstock was not a
significant factor in the dried vine fruit yield response of Sultana to
nitrogen supply.
PERENNIAL RYEGRASS CULTIVARS