Gin damaged seeds may exceed 10 percent and such seed will produce
abnormal seedlings.
Seeds with a germinative ability or less than 80 percent should not
be used.
The content of free fatty acids in the seeds may vary from 0.5 to
8 percent, the higher the fatty acid content of the seed is the lower
will be the germination rate. Hence, seeds that have a fatty-acid content
in excess of 0.75 percent should not be used for sowing.
The rapidity of germination is also an important characteristic of
the seed. It is considered satisfactory if two-thirds of the seeds germinate
in one-third of the time that is considered necessary for the completion
of germination.
A number of cotton diseases are seed-borne. Before selection and
sowing of seed ensure that the seed is disease-free.
Delinting
Fuzz makes the seeds cling together, thus hampering their free
passage through the bowls and tubes of the indigenous seed drill.
To remove fuzz, rub the seed with mud, or a mixture of earth
(or ash) and fresh cow-dung.
The seed is treated with strong commercial sulphuric acid, which burns
the fuzz, or with chloride of zinc, which dissolves the short fibre.
In the case of sulphuric acid treatment, the seeds are soaked for
two minutes in it, then taken out and washed in running water to remove
the chemical.
In the case of chloride of zinc treatment, the seeds are immersed
in its solution for ten to fifteen minutes and then washed.
The chemical treatments not only remove the fuzz, but they are also
said to improve the germinating capacity of the seed, hasten germination
and make for easier handling of seed.
However, these processes are not only costly but also have to be
used with caution to avoid injury to the seed.
They are therefore not recommended.
Seed soaking
Soaking of desi cotton seed for two or three hours and that of fuzzy
American varieties for four to six hours in water before treatment with
mud and cow - dung, hastens germination and there by gives a better
start to young seedlings and also ensure a more uniform stand of plants.
The soaking of seed before sowing is a common practice in many parts
of the country but where it is not so, it should be advocated for both
irrigated and rainfed cottons. Insect-damaged and immature seed floating
on the surface of water is removed and discarded.
The benefits are more pronounced in the case of American varieties
and the re-sowing of gaps in a rainfed crops.
Seed Treatment
Seeds required seed treatment before planting.
Depending on the requirement one or more of the following seed
treatments may be undertaken.
Chemical seed treatment
Bacterial inoculum
Chemical treatment
Against seed born diseases.
Soak the acid delinted seed in 2 grams of carbendazim or 3 grams of
mancozeb dissolved in 1 litre of water.
Or
Slurry treatment
Captan at 2 grams per kg of delinted seed with 5 ml of water per kg
of seed.
Bacterial inoculum
Azotobacter
A free living heterotropic nitrogen fixing bacteria - Inoculate seed
with appropriate strain of bacteria.
Significant inoculant response at different places range from 34
to 247 kg N/ha.
Azospirillum
An associative micro aerophylic Nitrogen fixer. It is possible to
reduce nitrogen requirement 25-30% by seed inoculation.
Mycorhizae : Vascular Arbuscular
Mycorhizae (VAM)
VAM has important effects on phosphorus uptake by plants and availability
of other nutrients like Zn, Cu, K,S, Al, Fe etc., Further VAM inoculation
improves water relations in plants - Reduces fertilizer requirement
by 25-30%.
Phosphatic Bio-fertilizer
Phosphatic solubilising organisms such as VAM, Aspargillius, Awamori,
Penicillium digetatum can grow with insoluble phosphatic sources and
convert them into soluble forms, to make them availability to crop plants.
Note:
Bacterial cultures can be obtained from Bio-fertilizers scheme ANGRAU
Amaravathi or UAS, Bangalore or Department of Micro Biology IARI, New
Delhi.
The optimum number of plants per unit area, and the distance between
and within the rows depend on the inherent vegetative habit of a variety
and conditions of soil fertility, soil moisture and cultural practices.
For instance, the optimum number of plants per unit area in the case
of a highly branched monopodial variety is much less than that in the
case of a non - branching, sympodial type.
Similarly, under conditions of good plant growth, such as, greater
fertility of the soil, availability of irrigation facilities and early
sowing, the number of plants per unit area (particularly of varieties
having tall, vigorously branching plants) has of necessity, to be smaller
than on relatively poor soil, or under late sowing and un-irrigated
conditions in which the plants do not make a vigorous growth and the
per plant yield is relatively low.
In case of non - branching varieties, on the other hand, close spacing
gives the best results even on rich soils.
The optimum number of plants under different conditions varies widely
and has to be secured by judicious variations of spacing and seed rate.
In working out proper seed rate for a variety for a given set of
environmental or cultural conditions, due allowance has to be made for
the spacing adopted, the seed size, the germination capacity of the
seed and the mortality of the plants caused by diseases, insect pests,
vagaries of the season and physiological disorders.
In the case of American cottons the relative fuzziness of the seed
has also to be taken into account. However, it may be stated, that in
actual practice, most of the cotton growers do not adjust the seed rate
to the optimum number of plants suitable heavy seed rate to provide
against failure of germination and mortality or young seedlings due
to pest or disease or other natural calamities.
A large number of seeds is also believed to help the emergence of
seedlings through surface crust.
Only the intelligent farmers who make due allowance for these factors
and adopt a wider spacing in the case of more fertile soils, and closer
spacing when the crop is sown rather late in the season or is grown
on rather poor soil.
Late sown crops and those grown on less fertile soils have to make
up the deficiency of yield by a greater number of plants per unit area.
In intercropping, the seed rate for cotton is not materially reduced
if the rows of the subsidiary crop are placed at relatively long intervals.
Time of sowing
Early sowing of cotton is important for a number of reasons:
It makes possible the most efficient use of precipitation, whether
stored in the soil or occurring during cotton growth.
Flowering and boll formation (first flush particularly) occur before
the month of September usually a wettest month.
The cotton matures before the onset of cold temperatures, detrimental
to boll bursting and the boll maturation period becomes progressively
longer.
Delayed sowing results in delayed flowering and this reduced flower
and boll number. Boll size is unaffected.
Fibre characteristics are only slightly influenced by delayed sowing.
Sowing Techniques
Crop is usually sown in lines with the help of bullock drawn seed
drill to facilitate periodical harrowings.
In case of hybrids/high yielding varieties/cotton grown in heavy
soils it is preferred to sow the seed by dibbling.
Under conditions of intensive cultivation, the dibbling of seed produces
very good results by securing a uniform stand of properly spaced plants.
This should be recommended particularly in tracts in which the sowing
of the crop is not necessarily to be completed in one or two days but
can be spread over a longer period.
Dibbling also produces good stand of plants under conditions of different
soil management.
Seeds are dibbled on the top of ridge at a depth of 25-30 mm. Seeds
sown to greater depths may fail to emerge.
Seeds can be sown on a pre-soaked ridge or on dry ridges, which are
soaked later by allowing irrigation water in furrows.
Ridge sowing ensures better aeration and regulated water supply to
the developing seeds.
Sowing on ridge results deeper roots and better root system.
Depth of sowing
Cotton is very sensitive to an excessive sowing depth and
should not go beyond 5 - 6 cm.
Gap filling
Death of a few plants, whatever the cause, is ignored or considered
only the natural way of reducing over crowding.
Such natural thinning affords to the remaining plants a chance
for better growth, particularly If the variety cultivated has
a good branching habit.
The smaller gaps are covered up by more vigorous growth of plants
and the crop yield does not suffer. In some cases, it may actually benefit.
Observations showed re-sowing of gaps aggregating upto 20 percent of
the stand did not increase the yield. Patches of this degree can be
safely ignored; particularly if the variety is a monopodial type and
the optimum sowing period is almost passed.
It has been observed that resowing rather late, say 4 - 5 weeks after
the original seedling, is not of much benefit.
The plants from such late sowings do not make good growth and seldom
produce a normal crop. Even plants from re-sowings done only 10 -15
days after the first sowing rarely catch up with the earlier sown plants.
They remain stunted and produce very few or no balls.
Thinning
Excess plants should be thinned as soon as the plants are about 10
- 15 cm height and have two pairs of 'true' leaves.
Earlier thinning is not desirable, the danger or seedling loss due
to unforeseen damage to seedlings.
Delayed thinning is also having undesirable effects like disturbing
the adjacent plants by due to excessive root development by the time
of thinning.
Ikisan - Plant density and crop performance in cotton
Plant density and crop performance
In dense - population, vegetative growth is curtailed and very few
or no vegetative branches are formed. The number of bolls per plant
is the only character affected by plant densities, the number of seeds
per boll, the total weight of the individual seeds and the amount of
fibre per seed are almost unaffected. Therefore, plant density affects
yield mainly by determining the number of bolls per unit area.
Excess plant density may delay maturity, probably because conditions
for boll maturation become less favourable.
Excess plant density leads to lodging some times.
A dense stand may reduce the evaporation from soil and competes effectively
with weeds.
Dense stand may avoid crusting of soil - more rapid and uniform development
of plants.
The above advantages are seen - provided the density is not excessive.
In order to ensure the required plant density, in some places sowing
more seeds than are required for producing the desired number of plants,
when the plants have reached a stage of development, the plants are
thinned to the desired stand.
Plant density or otherwise spacing adopted between and within the
rows is mainly depends on the species chosen and the plant type of the
variety.
Crop Establishment
