Journal of the Department of Agriculture, Journal of the Department of Agriculture, Western Australia, Series 4 Western Australia, Series 4
Volume 1
Number 8 August, 1960 Article 7
1-1-1960
Tobacco seed-bed management Tobacco seed-bed management
A E. Baker
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Recommended Citation Recommended Citation
Baker, A E. (1960) "Tobacco seed-bed management," Journal of the Department of Agriculture, Western Australia, Series 4: Vol. 1: No. 8, Article 7.
Available at: https://library.dpird.wa.gov.au/journal_agriculture4/vol1/iss8/7
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SEED-BED MANAGEMENT
i
by A. E. BAKER, Tobacco Adviser
A SUCCESSFUL tobacco crop depends initially on a n ample supply of well-grown,
* • - disease-free seedlings available early in t h e planting season. If planting is held up due to a poor supply of seedlings, t h e resulting crop will not be grown in t h e most favourable p a r t of t h e season. Late-grown crops nearly always give low r e t u r n s .
I n determining t h e site for seed-beds, t h e availability of water should be con- sidered. A good supply of w a t e r which c a n be used from a hose is essential for t h e production of tobacco seedlings.
Seed-beds should face approximately n o r t h - e a s t so a s to benefit from t h e greatest a m o u n t of sunshine. Protection from prevailing southerly a n d westerly winds is also a n a d v a n t a g e in keeping t h e soil warm.
T h e desirable soil for seed-beds is a friable sandy loam; most tobacco soils are suitable for t h i s purpose.
Most seed-beds are constructed w i t h t i m - ber frames about 16 ft. in l e n g t h a n d 3 i ft. in width. Larger sized beds m a y be used though a n y t h i n g over 4 ft. in width is inconvenient to reach over w h e n apply- ing benzol a n d h a n d l i n g t h e p l a n t s .
Unbleached calico covers fitted to wooden or pipe rollers a r e used to confine t h e benzol vapour a n d to protect t h e seedlings from frost or heavy rain.
SOIL PREPARATION
It is an a d v a n t a g e to t r e a t t h e soil for t h e control of weeds, n e m a t o d e s a n d diseases prior to sowing. One of t h e most effective agents for controlling weeds, nematodes a n d diseases is t h e gas, m e t h y l bromide.
This chemical c a n be p u r c h a s e d in 1 lb.
tins a n d is used a t t h e r a t e of 1 lb. per 100 square feet of seed-bed a r e a . Thus two 16 ft. x 3 ft. beds could be treated with one pound of m e t h y l bromide. To apply this gas to t h e soil a plastic sheet
is laid over t h e seed-bed frame a n d t h e edges of t h e sheet are covered with soil in order to make a gas-tight seal. By
A 9 ft. x 3 ft. seed-bed with centre ridge-pole removed to show good even germination of seedlings. Note that few benzol tins are used In the early stages of seedling
growth
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m e a n s of a r u b b e r tube w h i c h is passed u n d e r t h e plastic sheet a n d a n a d a p t o r which fits onto t h e c a n of m e t h y l bromide, t h e gas is released u n d e r t h e cover.
T h e plastic cover, which holds t h e gas in c o n t a c t w i t h t h e soil, is left in place for 24 h o u r s if t h e w e a t h e r is fine a n d t h e soil is n o t too wet, or for 48 hours if t h e w e a t h e r is cold a n d t h e soil is over-moist.
At t h e end of t h i s period, t h e sheet is removed a n d t h e bed can be p l a n t e d after 48 h o u r s exposure to t h e air. T h e one plastic cover m a y be used in r o t a t i o n for t r e a t i n g all t h e beds.
Higher r a t e s t h a n 1 lb. of m e t h y l bromide per 100 square ft. of bed m a y be used if t h e beds sizes a n d plastic sheet sizes do n o t work out evenly. T h e r a n g e between 1 lb. of m e t h y l bromide per 100 square ft.
a n d 1 lb. p e r 50 square ft. is satisfactory except t h a t t h e h i g h e r r a t e s are more expensive.
If care is t a k e n t o see t h a t t h e r e are no s h a r p corners or nails on t h e seed-bed frames which would p u n c t u r e t h e plastic sheet, such a sheet should last for several seasons.
Warning.—Methyl bromide is a poison- ous gas a n d should be h a n d l e d carefully.
Do not b r e a t h e t h e vapours. Each can of m e t h y l bromide c o n t a i n s t e a r gas which causes t h e eyes to b u r n , a n d t h i s serves t o w a r n of gas leakage d u r i n g storing or h a n d l i n g . Be s u r e to read directions on t h e c a n before applying m e t h y l bromide.
O t h e r seed-bed t r e a t m e n t s which are sometimes used a r e formalin a n d allyl alcohol. F o r m a l i n is useful for t h e control of soil-borne diseases but controls weeds a n d n e m a t o d e s only to a limited extent.
Allyl alcohol is only useful for t h e control of weeds.
FERTILISER
Many growers in t h e past have used far too m u c h fertiliser on seed-beds a n d this h a s caused widespread seedling injury.
Before p l a n t i n g t h e beds, a dressing of l i lb. of low p o t a s h (5.7 per cent.) tobacco fertiliser or p o t a t o m a n u r e " B " should be applied per square y a r d of soil. T h e correct q u a n t i t y of fertiliser per bed should be weighed out so a s to ensure t h a t t h e right a m o u n t is applied. T h u s a 16 ft. x 3£ ft.
bed h a v i n g a n a p p r o x i m a t e a r e a of six s q u a r e y a r d s will require 9 lb. of fertiliser.
T h e fertiliser is spread evenly over t h e surface of t h e bed a n d mixed i n t o t h e t o p two or t h r e e i n c h e s of t h e soil. Deep dig- ging in of this fertiliser should be avoided otherwise t h e seedling roots m a y n o t r e a c h t h e fertiliser a n d t h e resulting growth will be poor.
SEEDING
As a result of poor g e r m i n a t i o n s in t h e past, growers c o n t i n u e to p l a n t tobacco seed a t very heavy r a t e s in order to over- come this trouble. Poor g e r m i n a t i o n h a s usually been caused by t h e use of too m u c h fertiliser or by dry soil conditions or a combination of b o t h t h e s e factors.
If seed-beds a r e m a n a g e d properly, a good stand of p l a n t s m a y be obtained by sowing not more t h a n 1 oz. of tobacco seed per 100 square y a r d s . W i t h a bed 16 ft. x 3£ ft. having a n a r e a of 6 s q u a r e yards, a level teaspoon of seed is sufficient. This seed is mixed w i t h clean s a n d or fine wood a s h a n d sprinkled evenly over t h e whole bed. The back of a r a k e m a y be used to press t h e seed i n t o t h e soil a n d to firm down the top of t h e soil.
I t is a n a d v a n t a g e to spread a t h i n layer
—no more t h a n i in. thick—of clean coarse creek-bed s a n d over t h e surface of t h e bed to cover t h e seed. This coarse s a n d p r o - tects the g e r m i n a t i n g seed from drying out a n d also p r e v e n t s it from being washed out by heavy w a t e r i n g . It is w o r t h r e m e m - bering t h a t s a n d which is used to mix w i t h t h e seed for sowing a n d s a n d used for covering t h e seed should be t r e a t e d with m e t h y l bromide, otherwise weeds a n d disease organisms m a y be introduced into t h e clean beds. A small h e a p of sand for t h i s purpose m a y be placed n e x t to one of t h e beds a n d t r e a t e d w i t h m e t h y l bromide at t h e s a m e time a s t h e bed is t r e a t e d .
CARE OF SEED-BEDS Watering.
Probably t h e most common cause of failure with tobacco seed-beds is in not keeping t h e soil surface sufficiently moist d u r i n g t h e g e r m i n a t i o n period.
As it takes a p p r o x i m a t e l y t h r e e weeks for tobacco seed to g e r m i n a t e in July a t Manjimup, t h e soil surface m u s t be kept moist during t h e whole of t h a t period. I n fine windy w e a t h e r , frequent light w a t e r - ings by h a n d hose will be necessary.
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Benzol.
I n t h e M a n j i m u p district, blue mould seldom a t t a c k s seedlings earlier t h a n three weeks after g e r m i n a t i n g . W h e n the seedling p l a n t s are about t h e size of a t h r e e p e n n y piece, benzol should be used in t h e beds every n i g h t .
T h e evaporating tins used to hold t h e benzol should not be deeper t h a n one inch a n d about 3 to 4 in. wide. T h e full t r e a t - m e n t should consist of one square inch of benzol surface to every 100 square inches of seed bed a r e a . T h u s a 16 ft. x 3£ ft. bed will have a n a r e a of 8,064 square inches.
Divided by 100, t h i s equals 80 square inches of benzol surface required.
If t h r e e - i n c h diameter r o u n d t i n s are used, each will h a v e a n a r e a of seven square inches. T h e n 80 divided by 7 indi- cates t h a t 11 t i n s are required for each seed-bed.
I n t h e early stages, when t h e seedlings are young, t h e y should n o t be subjected to t h e full benzol t r e a t m e n t otherwise i n - jury will occur. Begin with half t h e n u m - ber of tins per bed, a n d gradually increase t h e n u m b e r a s t h e seedlings grow. Benzol in t h e liquid s t a t e is fatal to seedlings and t h e greatest care should be exercised to prevent spilling or splashing when t h e tins are being filled.
Diseases.
I n addition to blue mould, t h e n e x t most common disease occurring in seed-beds is damping-off. T h i s fungal disease a t t a c k s the seedlings a t ground level a n d may also be associated with various root- rotting organisms. One of t h e most common causes of t h i s disease is over- crowding of seedlings due to too m u c h seed being planted. By fumigating t h e soil prior to p l a n t i n g ; by not sowing t h e seed too heavily, a n d by allowing t h e beds to r e - main open to t h e sun a n d air d u r i n g t h e growth of t h e seedlings, m u c h of t h e risk of damping-off disease will be overcome.
A further operation in t h e prevention of damping-off or in t h e control of t h e disease if it does occur, is t h e use of Cheshunt mixture. One ounce of Cheshunt mixture is dissolved in two gallons of water a n d this solution is watered onto t h e beds.
This solution should be washed off t h e leaves with clean water in order to prevent burning. Cheshunt mixture m a y be used twice weekly if damping-off is prevalent in the seed-beds.
As Cheshunt solution a t t a c k s galvanised watering cans, it is advisable to use a copper or plastic watering can for t h e application of this chemical.
Mosaic disease is frequently present in manufactured tobacco so t h a t people who smoke often infect seedlings with t h e i r h a n d s . Before a n y seedlings are h a n d l e d or pulled, t h e h a n d s should be thoroughly washed with soap and water. Do n o t smoke whilst handling or pulling seedlings.
GROWTH OF SEEDLINGS
If seedlings are backward in growth or inclined to be yellow, they m a y be helped with some liquid m a n u r e . For this purpose a small handful of n i t r a t e of soda or sul- p h a t e of ammonia mixed in four gallons of water may be watered on to t h e beds.
Immediately after this t r e a t m e n t , t h e beds should be watered with plain water so as to wash t h e fertiliser off t h e leaves. Urea may be used instead of n i t r a t e of soda or sulphate of ammonia, to stimulate growth of the seedlings. As urea h a s twice t h e quantity of nitrogen as these other fer- tilisers, only half the quantity should be used at a time. A heaped tablespoon of urea in four gallons of water should be sufficient.
Seedlings should be hardened off by r e - ducing the watering during t h e week or so before planting out in t h e field. By allow- ing the seedlings to wilt a little in t h e beds a t this stage, they will be toughened u p and t h e n will be more able to w i t h s t a n d the shock of t r a n s p l a n t i n g in t h e field.
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