Winter wheat
(Triticum aestivum) planting in Nebraska is recommended for mid-September,
but summer crops are often harvested in late September and early October. Also,
weather may delay planting.
Gibberellin, first identified from a pathogenic fungus, is a family
of natural growth promoters of which gibberellic acid (GA3) may be
the most active in stimulating stem elongation. GA3 bioassays for
stem growth were reported on common bean and winter wheat demonstrating
differential sensitivity of cultivars and growth habits.
In this paper, between 2005 and 2011, field trials were conducted on
winter wheat (Triticum aestivum L.) cultivars Goodstreak and Wesley and between
2007 and 2009, on winter rye (Secale cereale L.) cultivar Rymin at the University
of Nebraska’s Panhandle Research & Extension Center, Scottsbluf. All plots
in all trials were four rows with spacing of 30 cm. GA3 was applied
as Release LC, a 4% a.i. by weight formulation, i.e., 1 g GA3/30mL, formulation (Valent BioScience
Corp., Long Grove, IL). Release LC was serially diluted with water to achieve
desired concentrations. In 2009 and 2010, 6-benzyl adenine (6BA) as MaxCel, a
1.9% a.i. by weight formulation (Valent Bioscience) was added to GA3.
For seed dip treatments used in all years, sufficient seed was weighed to plant
20 plots and treat with 1 L of water, GA3 solution, or GA3 + 6BA solution.
The results showed that heights in mid Nov showed a reduction with
later planting. When planted about 1 Oct and 15 Oct, the delayed growth of
Goodstreak, compared to planting two weeks earlier, was fully overcome by GA3 at
250 ppm. For Wesley, 1000 ppm GA3 was needed to nearly overcome
later planting. Rymin rye gave an intermediate response between the two wheat
cultivars. Spring and summer heights were not affected by GA3.
Spring biomass, yield and harvested seed germination showed no GA3 effect.
In later trials (planted in 2009 and 2010), the cytokinin 6-benzyl adenine
(6BA) was added to GA3 to stimulate tiller formation. In the 1st year,
6BA at 2000 ppm depressed height, weight and yield without tiller promotion.
Repeating the trial with lower rates (31 - 125 ppm 6BA) did not offer an
additional advantage to GA3.
This study demonstrated that GA3 applied directly to seed
would stimulate pre-winter seedling growth when seeds were planted from mid Sep
to mid Oct. With GA3 application, a two-week delay in planting could
be overcome. This would result in the plant size and stand to be sufficient to
resist wind-induced soil erosion during the winter and stabilize the field even
though the field was planted later than recommended. This would also improve
crop rotation when wheat is planted after a summer crop that is harvested in
late September or early October. Furthermore, GA3 gives an
additional production practice in case of adverse weather resulting in delayed
planting. Besides, considering its potential uses, applying GA3 to
seed can be considered as an “insurance policy” but its cost needs to be
considered as well.
Article by Alexander D. Pavlista, et
al, from USA.
Full access: http://suo.im/51BtxB
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