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The effect of defoliation for winter forage on recovery and grain yield of barley and oats in Tasmania

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Abdul-Rahman, MS (1988) The effect of defoliation for winter forage on recovery and grain yield of barley and oats in Tasmania. PhD thesis, University of Tasmania.

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Abstract

Experiments were carried out between 1983 and 1987 at the University
Farm in Southern Tasmania to compare the winter oats cultivar, Esk
(prostrate, dual-purpose), with a range of barley cultivars: Shannon
(spring, erect habit of growth, two-row grain type), Malebo (erect,
six-row forage type), Triumph (spring, semi-prostrate, two-row grain
type), and WU3072 (winter, prostrate, two-row grain type).
In a preliminary experiment on Esk oats, nitrogen fertilizer
promoted recovery after grazing by increasing tillering, leaf area
and radiation interception, and by delaying leaf senescence.
The rapid winter growth of erect barley cultivars provided
substantial amounts of dry matter (1.5 - 2.3 t/ha) for winter
grazing. However, the shoot apices on the mainstems of these
cultivars developed rapidly below the soil surface and emerged above
ground level as much as 6-8 weeks before those of the prostrate
cultivars, thus curtailing the "safe" period for grazing. Malebo
exceeded Triumph in yield of digestible dry matter prior to winter
grazing. The lowest level of crude protein at grazing was found in
Esk oats.
Although tiller numbers were increased following defoliation,
leaf production was more important for recovery. Faster regrowth
after defoliation, better radiation interception, greater efficiency
of crop regrowth and higher final forage and grain yields were
achieved by Malebo and WU3072 compared to Shannon and Triumph. The
erect Malebo replaced leaf area rapidly after defoliation, through
the production of longer, wider and thicker leaves. The prostrate
WU3072 retained considerable leaf area after defoliation. In glasshouse experiments, the rate of movement and
development of the mainstem apex was less sensitive to high
temperature in Malebo than in Shannon and Triumph. Esk oats was
shown to respond strongly to vernalization and photoperiod,
resulting in both stability in flowering time and late flowering
after the time when frosts were likely to occur. The barleys,
to vernalization
however, varied in their responses 4 from moderate in WU3072 to weak
or nil in the spring cultivars, and hence ear emergence, even after
early defoliation, occurred several weeks earlier than in Esk oats.
In the field experiments, differences between cultivars in
total dry matter at the dough stage of development were not large.
Esk generally gave the highest yield of dry matter when
undefoliated, but following early defoliation, Malebo produced over
2 t/ha more than Esk.
The lowest grain yield and harvest index was in Esk. Early
defoliation did not significantly reduce grain production in any
cultivar, whereas a single defoliation in late winter or two
defoliations (early and late) drastically reduced grain yield
because of the removal of growing points on the mainstems and
primary tillers. WU3072 was more tolerant of late defoliation than
other barley cultivars because of its residual leaf area and delayed
reproductive development. Its advantage in grain yield came from
2 more ears per m and more grains per ear.

Item Type: Thesis (PhD)
Keywords: Barley, Oats, Barley, Oats
Copyright Holders: The Author
Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1989. Bibliography: p. 233-251

Date Deposited: 25 Nov 2014 00:44
Last Modified: 23 Aug 2017 01:23
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