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II. Origin and Characteristics of Classes of Tobacco

II. Origin and Characteristics of Classes of Tobacco

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214



C. B. MCCANTS AND W. G. WOLTZ



the discovery of the Americas, the natives of Central and South America

and the Islands were probably growing various strains of N . tabacum

while those along the eastern seaboard of North America were growing

strains of N . rzlstica.

The nucleus from which the tobacco industry in the United States

expanded is probably the commercial planting by John Rolfe in Jamestown, Virginia, in 1612. At the outset or very shortly thereafter, N .

rusticu, the species grown by the natives, was supplanted by N . tubacum,

the seed for which was obtained from South America or the West Indies.

As the culture of tobacco expanded, several things happened which

resulted in a change in the characteristics of the leaf. Initially, new and

different soil types and fertilization and cultural methods were

employed. Then growers began to select from the heterogeneous sorts

that were available, plant types that suited their fancy. Thus, selection

pressure, culture and management practices, soils, and climate each

played a role in developing the present classes and types of tobacco.

With increasing specialization in tobacco manufacturing, first in the

production of snuff and pipe tobacco and subsequently in the manufacture of chewing tobacco, cigars, and finally cigarettes, it was observed

that the leaf from a particular area or areas was more suited for the

manufacturing of one product than another. For example, the characteristics of the fire-cured class, i.e., dark in color, thick, oily, tough, and

high in nicotine, make the leaf particularly desirable for snuff and

chewing tobacco. The development of these leaf characteristics is

favored by fertile clay soils, high levels of nutrients, low topping, and

wide spacing of plants. At the other extreme, a light-colored leaf,

medium to low in nicotine and medium to thin in bodyz is desirable for

manufacturing cigarettes. The production of this type of tobacco is

favored by sandy textured soils that have moderately low levels of

nutrients, by close plant spacing and by moderately high topping.

Thus, the physical and chemical properties of the soil, fertilization, and

management practices suitable for the successful production of tobacco

used principally in one type of product may be different from those

required for a different commercial product.

Within recent years there has been an expansion in production outside of the historical production centers due primarily to monetary

problems and to tariffs and other trade restrictions. Although the tobacco

’“Body is a technical trade term of great significance to judges of tobacco and

cannot readily be given an exact scientific definition. It is essentially an empirical

judgement of substance content and is not related to thickness, weight per unit

area or density as such. Its opposites are washed out or chaffy” (Darkis et al.,



1935).



TOBACCO GROWTH AND NUTRITION



215



produced in these areas has found its way into consumer products, it

is generally recognized that it does not possess the aroma, flavor, or

other physical and chemical characteristics historically associated with

traditional quality leaf. Although intensive research and development

on varieties and cultural practices have resulted in some improvements

in leaf quality, it is not yet possible to produce tobacco in the new

areas with quality characteristics as desirable as those in leaves from

the traditional production centers, This evidence further illustrates the

important influence of the soil characteristics and climatic regimes on

the growth and development of the plant into a commercially desirable

product.

111.



Seedling Growth



The seeds of N . tabacum are very small; there are 300,000 to 400,000

per ounce depending on the variety and conditions under which they

are grown. To our knowledge the direct planting of seeds in the field

has not been successful although it has been attempted. In most of the

areas where the crop is grown the seeds are shown in open beds protected by a covering of cheesecloth or some strawlike material; in the

cooler regions, seedlings are produced in greenhouses or cold frames.

Seeds of some varieties require light for germination. Daily alternations of moderately high and low temperatures, however, may

largely overcome the need for light (Kincaid and Gratz, 1935). Optimal

temperature for germination is about 75°F. Germination ceases at

temperatures below 45°F. and above 90°F. (Bunn and Splinter, 1961).

Emergence of the seedling to the surface is severely impeded when

the depth of planting is greater than 5 to 10 mm. (Seltmann, 1963; Pal

and Bangarayya, 1965). The deeper the planting, generally the longer

the time required for the seedlings to emerge to the soil surface. Deep

planting also delays the growth of the roots, and this retardation in root

growth coupled with delayed emergence continues to influence the

growth of the seedlings for 30 days or more. Since tobacco seeds are

planted on or very near the surface of the soil, the maintance of proper

moisture conditions around the seed is very difficult, particularly during

dry, windy periods in open plant beds. The influence of moisture

conditions on seedling development is compounded by the high rates

of fertilizer applied to the plant beds and the shallow application of the

fertilizer. Under dry conditions the soluble salt concentration frequently

results in injury to the seedlings. This damage is usually greatest at

the time of seed germination and in the early stages of growth (Bortner

et al., 1948).

When the plants are about 6 inches in height, they are ready for



216



C. B. MCCANTS AND W. G . WOLTZ



transplanting to the field. Larger plants tend to flower before they have

their full leaf complement; this results in fewer leaves per plant and

generally a lower yield. Smaller seedlings are more difficult to transplant

and do not live after transplanting as well as do medium size and larger

ones. Rapidly growing and succulent plants in the seedbed do not

live well or start new growth quickly after transplanting. Good livability

and rapid growth of new roots after transplanting is favored by a high

carbohydrate level in the seedlings (Dean et al., 1960),



IV.



Plant Growth and Nutrient Uptake



Although the quality of tobacco is a most important aspect of its

usefulness to the manufacturer, it is a difficult property to measure in

terms of specific chemical and physical characteristics. Because the

components of quality have not been quantitatively delineated, it is

not possible to study absolutely the influence of various growth factors

on quality. Nevertheless, there is a large body of qualitative evidence

which provides some indications of these relationships. The accumulated

mass of this evidence indicates that the quality characteristics are

intimately associated with the nature of growth of the plant from

transplanting through final harvest.

The tobacco plant, from seedling stage until final harvest, is

extremely sensitive to relatively small fluctuations in nutritional regimes

and environmental conditions. Changes which may appear to be slight

by visual standards, frequently result in distinguishable modifications in

the properties of the leaves and may influence their weight and commercial value. Thus some knowledge and consideration of the total

growth and development of the plant are essential to a complete

understanding of the nutrition of the plant.

A. GROWTH

CHARACTERISTICS

The total accumulation of dry matter by tobacco from the time of

transplanting in the field until final harvest is generally characterized by

a sigmoid curve. The data in Fig. 1 (see p. 239) were obtained with a

flue-cured type but are typical of this relationship. Under favorable

growth conditions, new roots can be seen the fourth day after transplanting, but no measurable increase occurs in the dry weight of aboveground parts until about 10 days later, and only small increases occur

during the subsequent 7 to 10 days. The period of major increase in

dry weight is normally from the fourth to eighth week after transplanting. With the onset of flowering, which occurs at 7 to 8 weeks after

transplanting in the field, there is a sharp decrease in the rate of dry

matter production, and this condition continues until final harvest.



TOBACCO GROWTH AND NUTRITION



217



In the commercial production of each type, under favorable temperature conditions, growth is most noticeably affected by the supplies of

available water and nitrogen in the soil. When the amount and distribution of rainfall were considered optimal, one-half of the total growth

during a 63-day period was found to occur during the fifth to seventh

week after transplanting; with poor rainfall distribution conditions,

however, one-half of the total growth was made during the seventh

to ninth week after transplanting (Grizzard et al., 1942). Over a fiveyear period, the beginning of grand growth for Havana seed tobacco

was found to vary from 30 to 50 days after transplanting depending on

environmental conditions early in the season (Morgan and Street, 1935).

The total amount of dry matter produced was lowest in the year when

initiation of major growth was the latest and highest in the year when

grand growth started the earliest after time of transplanting.

When other factors are not limiting, there is an increase in the rate

of growth as the level of available nitrogen increases from deficient to

adequate, For example, growth rate as measured by increase in height

was slow under deficient conditions but was rapid at a moderate level

of nitrogen. The sigmoid growth curve was best developed when

conditions were most favorable for slow rather than rapid growth

(Garner et al., 1934).

Studies with oriental tobacco showed that not only the total mass

of material produced, but also the growth curves for stems and leaves

were sigmoid (Wolf, 1947). It was also observed that the duration of

the period of expansion of leaves was similar at all stalk positions and

that the time required for leaves to obtain their maximal area was

about 3 weeks from the time they were sufficiently large to be measured.

Wolf concluded from his experience that, for oriental tobacco, the

best commercial product is produced when growth rates are slow and

uniform from the time plants are established until the leaves are

harvested; consequently, the growth curve for this class of tobacco

should approximate a straight line. Contrary to the effects reported by

Wolf with oriental tobacco, Raper (1966) has shown that for flue-cured,

the number of days required for leaves to reach their maximal area

and weight differs among stalk positions.

Attempts to describe the growth of tobacco by mathematical expressions apparently have been limited. The Mitscherlich equation was

applied to yield data for leaf and stalk and for the two combined, but

unsatisfactory results were obtained in that the computed yields varied

drastically from the actual yields (Garner et al., 1934). The value of

0.122 which Mitscherlich assigned to the proportionality constant C for

fertilizer nitrogen, was much too low to fit the yields actually obtained



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