Nursery area should be a good fertile piece of land nearer to the water source. It should have good drainage facility and located at an elevated place. The field should be fully exposed to sunlight. It should be devoid of any perennial weed infestation. Nursery site may be regularly changed so as to minimize the incidence of pests and diseases and weed infestation. This will also eliminate contamination of other varieties.
Seeds and Sowing
Seed rate depends on test grain weight, germination percentage, spacing to be adopted and number of seedlings to be planted. Seed rate for rice can be calculated using the following formula:
Seed rate (kg/ha) = 1000 grain weight (g) x Number of seedlings per hill / Spacing (cm2) x 100
Corrections are made for germination percentage and another 20% seed rate is added to cover the risk.
Irrigation is regulated until proper germination and establishment of the seedlings. The beds are allowed to saturate till the sprouts are about 5 cm in height and thereafter, a constant level of 2.5 cm or water may be maintained. Pre- emergence herbicide, butachlor or thiobencarb @ 1.0 kg a.i/ha is applied 8 days after sowing to control weeds in the nursery. A thin film of water is maintained at the time of herbicide application and then allowed to disappear. Adequate plant protection measures are required to guard against pests.
Nursery is manured with organic manure, FYM or compost @ one ton per 1000 rrf. At the time of nursery preparation, diammonium phosphate (DAP) @ 2 kg MO m is applied. If the seedlings show symptoms of N deficiency and the growth is not satisfactory, urea is top dressed at the rate of 500 g per 40 m2, 7-10 days prior to uprooting seedlings.
Optimum Age and Pulling out of Seedlings
Optimum age of seedlings is important, especially for the short duration rice varieties having a very short vegetative period. Seedlings are ready for transplanting at four leaf stage. Normally one week period of nursery for one month rice duration is the thumb rule. The duration of nursery is 21-25 days for short duration, 25-30 days for medium and 35-40 days for long duration varieties.
The dapog method of raising seedlings was developed in the Philippines. This involves growing seedlings on a concrete floor or on a raised bed of soil covered with polythene sheets. A small nursery area of 30-40 m2 is required for one ha of main field. Raised seed-beds are prepared after final land leveling and are covered with polythene sheets. Banana leaves with the midribs removed can also be used instead of polythene sheets. The polythene sheets prevent entry of roots into the soil. The dapog beds should be about 1.5 m wide and its length depends on the area to be planted. Pre- germinated seeds are sown on the top of the sheets at the rate of 2.0 kg/rrf of nursery. Water is sprinkled and the seeds are pressed gently with hand or with a wooden flat board twice a day for the first 3-6 days. This helps the roots to remain in contact with water retained on the surface and prevents drying. After six days, the seed-beds are watered up to a depth of 1-2 cm. In about 14 days, seedlings are ready for transplanting. By this time, the roots are well developed and interwine with one another so that the nursery can be cut into stripes, rolled and transported easily to the planting site. One m2 of dapog nursery can be used to transplant about 200 m2.
In places of water scarcity, raising of dry rice nursery is practiced. The nursery area is ploughed under dry condition and the field is brought to fine tilth. Light soils are preferred for dry nursery bed preparation. Farm yard manure or compost @ 12.5 t/ha is spread uniformly and incorporated into the soil, 2-3 weekk before sowing. Long beds of convenient length and 1.0-1.5 m width are formed. Channels of 30 cm width between the beds are formed for irrigation.
The seeds are sown dry, either broadcast or in lines and covered with a thin layer of soil or compost. In some places, water is impounded into the bed and soil is stirred to form mud. After the clay particles settle, sprouted seeds are broadcast sown. Nursery beds are irrigated periodically. In dry areas and in calcareous and saline alkaline soils, chlorosis is the major problem in dry nurseries. Seed treatment with FeSO4 and flooding the soil may give some relief. The seedlings obtained from the dry nurseries are generally hardy and establish very fast in the main field.
Nursery Techniques for Tobacco
© 2018 Biocyclopedia | All rights reserved.