Another very important aspect to increase and maintain high production, the authors conducted a study to learn if mulching resulting in reduced stress could reduce the “small fruit” syndrome of Hass. Unexpected was the significant increase in yield and delayed seed coat senescence.
This is practical information that all farmers should pay attention to.
South African Avocado Growers Association Yearbook 1998. 21:26-2 B.N. Wolstenholme, C.S. Moore-Gordon & A.K. Cowan
ABSTRACT
Composted pine bark mulch was applied to a depth of 15 cm under the drip of 6 year
old Hass on Duke 7 trees at Everdon Estate, Howick in February 1993, and responses
compared with unmulched trees for three seasons. The hypothesis was that improved
root growth and health would reduce “stress”, leading to delayed seed coat senescence
and therefore larger fruit size. In spite of the comparatively cool, mesic, non-stressful
environment, fruit size was increased by an average of 7%, fruit number by 15% and
total yield by 23%. Mulched trees had lower leaf temperature, delayed seed coat
browning, and less pedicel ringneck (all manifestations of lowered stress), and improved
growth of “feeder” roots throughout the season.
The half-life of the particular compost was estimated at 5 years, so that the high initial
costs could be amortized over a long period. Mulching with suitable organic materials
(ideally with a carbon: nitrogen ratio between 30 and 100) is highly recommended in
most situations in avocado orchards, and even better results could be expected in more
stressful environments and where water is a limiting factor. The trial has also led to
detailed studies on the physiology of avocado fruit growth, which increases our
understanding of control mechanisms and their potential for manipulation. The role of
orchard mulching in the changing environment of the new millennium is discussed.
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