New Zealand Journal of Crop and Horticultural Science abstracts
Short communication
Control of willow-tree shelter root systems in kiwifruit orchards by root
pruning
K. A. HUGHES
W. R. N. EDWARDS
A. M. SNOWBALL
The Horticultural and Food Research Institute
of New Zealand
Private Bag 11030
Palmerston North, New Zealand
Abstract The root systems of willow-tree shelter root systems
and adjacent kiwifruit root systems, and measurements of gravimetric soil water
content, were mapped in three orchards on deep Te Puke soils, in the North
Island of New Zealand. Fruit yields were also obtained from the first (5-6 m
from the shelter) and middle (4th or 5th row, 19-24 m from the shelter) rows of
the sampled blocks. The three orchards were aged between 11 and 14 years, and
each used a different shelter root-pruning method, i.e., (1) regular annual
root pruning where shelter roots were cut on both sides of trees every spring
with a 0.8 m deep slit c. 2.5 m from the shelter; (2) occasional root pruning
where shelter roots had been cut once 2 years before the experiment; and (3) no
root pruning. Root-length density data were obtained from cores sampled
randomly in the 5-6 m headland region between the shelter row and the first row
of kiwifruit vines to 2 m depth, and from the first two rows of kiwifruit (up
to 10.2 m from the shelter) to 1 m depth. More dead roots were found in the two
root-pruned treatments between the pruning slits and the first row of kiwifruit
(P < 0.02). However, root pruning had no significant effect on live
willow roots in the adjacent two rows of kiwifruit
(P < 0.05). Mean live willow root-length densities over all
orchards in the 0-1 m layer were: 0.06 104m/m3 between the shelter and the 1st
row of kiwifruit; and 0.04 104m/m3 between the 1st and 2nd rows. Cumulative
distributions of ranked data were used to compare treatments. Root pruning
treatments had no significant effects on soil water contents
(P < 0.05), but soil water contents were significantly
lower within 5 m from the shelter (P < 0.001) compared to
more than 5 m distant. The data indicate that shelter roots quickly grow under
root-pruning slits and subsequent pruning is probably ineffective for
decreasing water competition in deep soils. Fruit yields and average fruit
weights did not differ between root pruning treatments, but the c. 50%
lower yields in the kiwifruit row adjacent to the shelter were in agreement
with other results which showed that shading from cloth substantially reduced
fruit yields.
Keywords Salix matsudana; root distribution; Actinidia
deliciosa; competition; pruning cuts
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