(part 3 of 6)

KENTUCKY.

Practically all of the hemp grown in the United States is from seed
produced in Kentucky. The first hemp grown in Kentucky was of European
origin, the seed having been brought to the colonies, especially Virginia,
and taken from there to Kentucky. In recent years there has been
practically no importation of seed from Europe. Remnants of the European
types are occasionally found in the shorter, more densely branching stalks
terminating in thick clusters of small leaves. These plants yield more
seed and mature earlier than the more desirable fiber types introduced from
China.
Nearly all of the hemp now grown in Kentucky is of Chinese origin.
Small packets of seed are received from American missionaries in China.
These seeds are carefully cultivated for two or three generations in order
to secure a sufficient quantity for field cultivation, and also to
acclimate the plants to Kentucky conditions. Attempts to produce fiber
plants by sowing imported seed broadcast have not given satisfactory
results. Seed of the second or third generation from China is generally
regarded as most desirable. This Kentucky hemp of Chinese origin has long
internodes, long, slender branches, opposite and nearly horizontal except
the upper ones, large leaves usually drooping and not crowded, with the
seeds in small clusters near the ends of the branches. Small, dark-colored
seeds distinctly mottled are preferred by the Kentucky hemp growers. Under
favorable conditions Kentucky hemp attains a height of 7 to 10 feet when
grown broadcast for fiber and 9 to 14 feet when cultivated for seed.

IMPROVEMENT BY SEED INTRODUCTION.

Without selection or continued efforts to maintain superior types,
the hemp in Kentucky deteriorates. As stated by the growers, the hemp
"runs out." The poorer types of plants for fiber are usually the most
prolific seed bearers, and they are often earlier in maturing; therefore,
without selection or roguing, the seed of these undesirable types increases
more rapidly than that of the tall, late-maturing, better types which bear
fewer seeds. New supplies of seed are brought from China to renew the
stock. Owing to the confusion of names the seed received is not always of
a desirable kind, and sometimes jute, China jute, or ramie seeds are
obtained. When seed of the ta-ma variety is secured and is properly
cultivated for two or three generations there is a marked improvement, but
these improved strains run out in less than 10 years.
The numerous trials that have been made by the Department of
Agriculture with hemp seed from nearly all of the sources mentioned and
repeated introductions from the more promising sources indicate that little
permanent improvement may be expected from mere introduction not followed
by breeding and continued selection. In no instance, so far as observed,
have any of the plants from imported seed grown as well the first year as
the Kentucky hemp cultivated for comparison. Further introduction of seed
in small quantities is needed to furnish stock for breeding and selection.
The most promising varieties for introduction are ta-ma and shan-ma-tze,
from China; Hiroshima and Tochigi, from Japan; Bologna, from Italy; and
improved types from Hungary.

IMPROVEMENT BY SELECTION

Kentucky hemp is reasonably uniform, not because of selection, or
even grading the seeds, but because all types have become mixed together.
Nearly all the seed is raised in a limited area. Hemp being
cross-fertilized, it is more difficult to keep distinct types separate than
in the case of wheat, flax, or other crops with self-pollinated flowers,
but it is merely necessary to isolate the plants cultivated for seed and
then exercise care to prevent the seed from becoming mixed. Until 1903 no
well-planned and continued effort seems to have been undertaken in this
country to produce an improved variety of hemp. At that time the results
of breeding by careful selection improved varieties of wheat and flax at
the Minnesota Agricultural Experiment Station were beginning to yield
practical returns to the farmers of that State. Mr. Fritz Knorr, from
Kentucky, then a student in the Minnesota College of Agriculture, was
encouraged to take up the work with hemp. Seed purchased from a dealer in
Nicholasville, Ky., was furnished by the United States Department of
Agriculture. The work of selection was continued until 1909 under the
direction of Prof. C. P. Bull, agronomist at the station. Points
especially noted in selecting plants from which to save seed for
propagation were length of internode, thinness of shell, height, and
tendency of the stems to be well fluted. The seasons there were too short
to permit selection for plants taking a longer season for growth. The
improved strain of hemp thus developed was called Minnesota No. 8. Seed of
this strain sown at the experiment station at Lexington, Ky., in 1910 and
1911 produced plants more uniform than those from unselected Kentucky seed,
and the fiber was superior in both yield and quality. A small supply of
this seed, grown by the Department of Agriculture at Washington, D. C., in
1912, was distributed to Kentucky hemp-seed growers in 1913, and in every
instance the resulting seed plants were decidedly superior to those from
ordinary Kentucky seed.
Seed selection is practiced to a limited extent on some of the best
hemp-seed farms in Kentucky. Before the seed-hemp plants are cut the
grower goes through the field and marks the plants from which seed is to be
saved for the seed crop of the following year. Plants are usually selected
for height, lateness, and length of internodes. Continued selection in
this manner will improve the type. Without selection continued each
season, the general average of the crop deteriorates.

CLIMATE.

Hemp requires a humid temperate climate, such as that throughout
the greater part of the Mississippi Valley. It has been grown
experimentally as far north as Saskatoon, in northwestern Canada, and as
far south as New Orleans, La., and Brunswick, Ga.

TEMPERATURE

The best fiber-producing types of hemp require about four months
free from killing frosts for the production of fiber and about five and
one-half months for the full maturity of the seeds. The climatic
conditions during the four months of the hemp-growing season in the region
about Lexington, Ky., are indicated by the following table:

Temperature and rainfall in the hemp-growing region of Kentucky (Henry,
Alfred Judson. Climatology of the United States. U.S. Department of
Agriculture, Weather Bureau, Bulletin Q, p.763, 1906.) (Insert table from
p. 305 here.)

Hemp grows best where the temperature ranges between 60 degrees and
80 degrees F., but it will endure colder and warmer temperatures. Young
seedlings and also mature plants will endure with little injury light
frosts of short duration. Young hemp is less susceptible than oats to
injury from frost, and fields of hemp ready for harvest have been uninjured
by frosts which ruined fields of corn all around them. Frosts are
injurious to nearly mature plants cultivated for seed production.

RAINFALL.

Hemp requires a plentiful supply of moisture throughout its growing
season, and especially during the first six weeks. After it has become
well rooted and the stalks are 20 to 30 inches high it will endure drier
conditions, but a severe drought hastens its maturity and tends to dwarf
its growth. It will endure heavy rains, or even a flood of short duration,
on light, well-drained soils, but on heavy, impervious soils excessive
rain, especially when the plants are young will ruin the crop.
In 1903, a large field of hemp on rich, sandy-loam soil of alluvial
deposit, well supplied with humus, near Gridley, Cal., was flooded to a
depth of 2 to 6 inches by high water in the Feather River. The hemp had
germinated but a few days before and was only 1 to 3 inches high. The
water remained on the land about three days. The hemp started slowly after
the water receded, but in spite of the fact that there was no rain from
this time, the last of March, until harvest, the last of August, it made a
very satisfactory crop, 6 to 12 feet in height. The soil, of porous,
spongy texture, remained moist below the dusty surface during the entire
growing season.

An experimental crop of about 15 acres on impervious clay and silt
of alluvial deposit, but lacking in humus, in eastern Louisiana was
completely ruined by a heavy rain while the plants were small.
The total average rainfall during the four months of the
hemp-growing season in Kentucky is 15.6 inches, as shown in the table on
page 305, and this is distributed throughout the season. When there is an
unusual drought in that region, as in 1913, the hemp is severely injured.
It is not likely to succeed on upland soils in localities where corn leaves
curl because of drought before the middle of August.

IRRIGATION.

In 1912, and again in 1913, crops of hemp were cultivated under
irrigation at Lerdo, Cal. The soil there is an alluvial sandy loam of
rather firm texture, but with good natural drainage and not enough clay to
form a crust on the surface after flooding with water. The land is plowed
deeply, leveled, and made up into irrigation blocks with low borders over
which drills and harvesting machinery may easily work. The seed is drilled
in the direction of the fall, so that when flooded the water runs slowly
down the drill furrows. Three irrigations are sufficient, provided the
seed is sown early enough to get the benefit of the March rains. The fiber
thus produced is strong and of good quality.

WEATHER FOR RETTING AND BREAKING.

Cool, moist weather, light snows or alternate freezing and thawing
are favorable for retting hemp. Dry weather, not necessarily free from
rain but with a rather low relative humidity, is essential for satisfactory
work in breaking hemp. The relative humidity at Lexington in January,
February, and March, when most of the hemp is broken, ranges from 62 to 82
per cent. The work of breaking hemp is rarely carried on when there is
snow on the ground. The work of collecting and cleaning hemp seed can be
done only in dry weather.

SOIL.

SOILS IN THE HEMP-GROWING REGION OF KENTUCKY.

The soil in most of the hemp fields of Kentucky is of a yellowish
clay loam, often very dark as a result of decaying vegetable matter, and
most of it overlying either Lexington or Cincinnati limestone. There are
frequent outcroppings of lime rock throughout the region. The soil is
deep, fertile, well supplied with humus, and its mechanical condition is
such that it does not quickly dry out or become baked and hard. The land
is rolling, affording good natural drainage.

HEMP SOILS IN OTHER STATES.

In eastern Nebraska, hemp has been grown on a deep clay-loam
prairie soil underlain with lime rock. In some of the fields there are
small areas of gumbo soil, but hemp does not grow well on these areas. In
California, hemp is cultivated on the reclaimed lands of alluvial deposits
in the lower valley of the Sacramento River. This is a deep soil made up
of silt and sand and with a very large proportion of decaying vegetable
matter. These rich, alluvial soils, which are never subject to drought,
produce a heavier growth of hemp than the more shallow upland soils in
Kentucky. In Indiana, crops of hemp have been grown in the Kankakee Valley
on peaty soils overlying marl or yellow clay containing an abundance of
lime. These lands have been drained by large, open ditches. There is such
a large proportion of peat in the soil that it will burn for months if set
on fire during the dry season, yet this soil contains so much lime that
when the vegetation is cleared away Kentucky bluegrass comes in rather than
sedges. It is an alkaline rather than an acid soil. The large amount of
peat gives these soils a loose, spongy texture, well adapted to hold
moisture during dry seasons. Water remains in the ditches 6 to 10 feet
below the surface nearly all summer, and the hemp crops have not been
affected by the severe drought which has injured other crops on the
surrounding uplands. In southeastern Pennsylvania, and in Indiana,
Wisconsin, and Minnesota, the best crops, producing the largest yields of
fiber and fiber of the best quality, have been grown on clay-loam upland
soils. In some instances, however, the upland crops have suffered from
drought.

SOILS SUITED TO HEMP

Hemp requires for the best development of the plant, and also for
the production of a large quantity and good quality of fiber, a rich, moist
soil having good natural drainage, yet not subject to severe drought at any
time during the growing season. A clay loam of rather loose texture and
containing a plentiful supply of decaying vegetable matter or an alluvial
deposit alkaline and not acid in reaction should be chosen for this crop.

SOILS TO BE AVOIDED.

Hemp will not grow well on stiff, impervious, clay soils, or on
light sandy or gravelly soils. It will not grow well on soils that in
their wild state are overgrown with either sedges or huckleberry bushes.
These plants usually indicate acid soils. It will make only a poor growth
on soils with a hardpan near the surface or in fields worn out by long
cultivation. Clay loams or heavier soils give heavier yields of strong but
coarser fiber than are obtained on sandy loams and lighter soils.

EFFECT OF HEMP ON THE LAND.

Hemp cultivated for the production of fiber, cut before the seeds
are formed and retted on the land where it has been grown, tends to improve
rather than injure the soil. It improves its physical condition, destroys
weeds, and does not exhaust its fertility.

PHYSICAL CONDITION.

Hemp loosens the soil and makes it more mellow. The soil is shaded
by hemp more than by any other crop. The foliage at the top of the growing
plants makes a dense shade and, in addition, all of the leaves below the
top fall off, forming a mulch on the ground, so that the surface of the
soil remains moist and in better condition for the action of soil bacteria.
The rather coarse taproots (Pl. XLI, fig. 3), penetrating deeply and
bringing up plant food from the subsoil, decay quickly after the crop is
harvested and tend to loosen the soil more than do the fibrous roots of
wheat, oats, and similar broadcast crops. Land is more easily plowed after
hemp than after corn or small grain.

HEMP DESTROYS WEEDS.

Very few of the common weeds troublesome on the farm can survive
the dense shade of a good crop of hemp. If the hemp makes a short, weak
growth, owing to unsuitable soil, drought, or other causes, it will have
little effect in checking the growth of weeds, but a good, dense crop, 6
feet or more in height, will leave the ground practically free from weeds
at harvest time. In Wisconsin, Canada thistle has been completely killed
and quack-grass severely checked by one crop of hemp. In one 4-acre field
in Vernon County, Wis., where Canada thistles were very thick, fully 95 per
cent of the thistles were killed where the hemp attained a height of 5 feet
or more, but on a dry, gravelly hillside in this same field where it grew
only 2 to 3 feet high, the thistles were checked no more than they would
have been in a grain crop. Some vines, like the wild morning-glory and
bindweed climb up the hemp stalks and secure light enough for growth, but
low growing weeds can not live in a hemp field.

HEMP DOES NOT EXHAUST THE FERTILITY OF THE SOIL.

An abundant supply of plant food is required by hemp, but most of
it is merely borrowed during development and returned to the soil at the
close of the season. The amounts of the principal fertilizing elements
contained in mature crops of hemp, as compared with other crops, are shown
in the accompanying table.

Amounts of principal fertilizing elements in an acre of hemp, corn, wheat,
oats, sugar beets, and cotton. (Insert first table from p. 310 here)

The data in the table indicate that hemp requires for its best
development a richer soil than any of the other crops mentioned except
sugar beets. These other crops, except the stalks of corn and the tops of
beets, are entirely removed from the land, thus taking away nearly all the
plant food consumed in their growth. Only the fiber of hemp is taken away
from the farm and this is mostly cellulose, composed of water and carbonic
acid.
The relative proportions by weight of the different parts of the
hemp plant, thoroughly air dried, are approximately as follows: Roots 10
per cent, stems 60 per cent, and leaves 30 per cent. (Peter, Robert.
Chemical Examination of the Ash of Hemp and Buckwheat Plants. Kentucky
Geological Survey, p. 12, 1884.) The mineral ingredients of these
different parts of the hemp plant are shown in the following table:
(Insert second table from p. 310 here)

The foliage, constituting nearly one-third of the weight of the
entire plant and much richer in essential fertilizing elements than the
stalks, all returns to the field where the hemp grows. The roots also
remain and together with the stubble, they constitute more than 10 per cent
of the total weight and contain approximately the same proportions of
fertilizing elements as the stalks. The leaves and roots therefore return
to the soil nearly two-thirds of the fertilizing elements used in building
up the plant.
After the hemp is harvested it is spread out on the same land for
retting. In this retting process nearly all of the soluble ingredients are
washed out and returned to the soil. When broken in the field on small
hand brakes, as is still the common practice in Kentucky, the hurds, or
central woody portion of the stalk, together with most of the outer bark,
are left in small piles and burned, returning the mineral ingredients to
the soil. Where machine brakes are used the hurds may serve an excellent
purpose as an absorbent in stock yards and pig pens, to be returned to the
fields in barnyard manure.

The mineral ingredients permanently removed from the farm are thus
reduced to the small proportions contained in the fiber. These
proportions, calculated in pounds per acre and compared with the amounts
removed by other crops, are shown in the following table:

Mineral ingredients removed from the soil by hemp, wheat, corn, and
tobacco, calculated in pounds per acre. (Peter, Robert. Chemical
Examination of the Ash of Hemp and Buckwheat Plants. Kentucky Geological
Survey, p. 17, 1884.)
(Insert table from p. 311 here.)

The hemp fiber analyzed was in the ordinary condition as it leaves
the farm. When washed with cold water, removing some but not all of the
dirt, the ashy residue was reduced more than one-third, and the total
earthy phosphates were reduced nearly one-half. The amount of plant food
actually removed from the soil by hemp is so small as to demand little
attention in considering soil exhaustion. The depletion of the humus is
the most important factor, but even in this respect hemp is easier on the
land than other crops except clover and alfalfa. The fact that hemp is
often grown year after year on the same land for 10 to 20 years, with
little or no application of fertilizer and very little diminution in yield,
is evidence that it does not exhaust the soil.

ROTATION OF CROPS.

In Kentucky, hemp is commonly grown year after year on the same
land without rotation. It is the common practice in that State to sow hemp
after bluegrass on land that has been in pasture for many years, or
sometimes it is sown as the first crop on recently cleared timberland. It
is then sown year after year until it ceases to be profitable or until
conditions favor the introduction of other crops. On the prairie soils in
eastern Nebraska and also on the peaty soils in northern Indiana, more
uniform crops were obtained after the first year. On some of the farms in
California hemp is grown in rotation with beans. Hemp is recommended to be
grown in rotation with other farm crops on ordinary upland soils suited to
its growth. In ordinary crop rotations it would take about the same place
as oats. If retted on the same land, however, it would occupy the field
during the entire growing season, so that it would be impossible to sow a
field crop after hemp unless it were a crop of rye. The growing of rye
after hemp has been recommended in order to prevent washing and to retain
the soluble fertilizing elements that might otherwise be leached out during
the winter. This recommendation, however, has not been put in practice
sufficiently to demonstrate that it is of any real value. Hemp will grow
well in a fertile soil after any crop, and it leaves the land in good
condition for any succeeding crop. Hemp requires a plentiful supply of
fertilizing elements, especially nitrogen, and it is therefore best to have
it succeed clover, peas, or grass sod. If it follows wheat, oats, or corn,
these crops should be well fertilized with barnyard manure. The following
crop rotations are suggested for hemp on fertile upland soils:
(Insert chart from p. 313 here).

Hemp leaves the ground mellow and free from weeds and is therefore
recommended to precede sugar beets, onions, celery, and similar crops which
require hand weeding. If hemp is grown primarily to kill Canada thistle,
quack-grass, or similar perennial weeds, it may be grown repeatedly on the
same land until the weeds are subdued.

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