Nursery Management and Seedling Production. Prepared by: Nercy M. Alvarado.
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Nursery Management and Seedling Production Prepared by: Nercy M. Alvarado
The first step in successful vegetable production is to raise healthy vigorous seedlings. Young plants whether propagated from seed or vegetatively require a lot of care particularly during the early stages of growth. They have to be protected from adverse temperatures, heavy rains, drought, wind and a variety of pests and diseases. If small seeded vegetables are sown directly in the field, germination is often poor and the young plants grow very slowly and require a long time to mature. Also the season may be too short for full development in the field.
To overcome these problems many vegetable crops are grown in nurseries before being transplanted in the field. A vegetable nursery is a place where plants are cared for during the early stages of growth, providing optimum conditions for germination and subsequent growth until they are strong enough to be planted out in their permanent place. A nursery can be as simple as a raised bed in an open field or sophisticated as a glass-house with micro-sprinklers and an automatic temperature control system. Although raising seedlings in a nursery has advantages, some vegetables do not transplant well, particularly root crops, and must be sown directly in the field for optimum results. It has to be noted, however, that transplanting seedlings interrupts their growth, which has the potential to reduce their vigor.
Although many vegetable seeds can be sown directly in the field, experience has shown that raising seedlings in a nursery has a number of advantages as discussed below. 1. Intensive care - Seedlings receive better care and protection (from animals, weeds and pests) in the nursery. The average garden soil is not an ideal medium for raising seedlings especially from the point of view of soil tilth. At an early stage of development most vegetable crops require special attention that is not possible in the main field.
2. Reduction of costs - Fewer seeds are used for raising seedlings in the nursery than for sowing directly in the field, because in the latter seedlings have to be thinned to one, which is wasteful. When expensive hybrid seeds are used, transplants therefore become more economically attractive. Pesticides and labor are also reduced under nursery conditions as compared to planting directly in the field.
3. Opportunity for selection - Raising seedlings in a nursery affords the grower an opportunity to select well grown, vigorous, uniform and disease free seedlings.
4. Extend a short growing season for late maturing crops - Seedlings can be raised in a nursery under a protected environment before conditions outside become suitable for growth and transplanted into the field when conditions allow, thus reducing the amount of time spent in the field.
5. Forced vegetable production for an early market - Generally prices of horticultural produce are attractive when production or supply is low. Vegetables can be grown ‘out-of-season’ in a nursery when conditions are not yet favorable. Such crops will thus mature earlier after transplanting and hence stand to fetch a higher price in the market.
There are three main facilities normally used for raising seedlings in a nursery. The choice of a particular one will depend on the available resources and prevailing environmental conditions. * Greenhouses - environment fully controlled * Net house - environment partially modified * Open field - where climatic conditions are normally favorable for the crops grown.
1.) Watering. The seedbed or seed box should be watered carefully with a fine stream of water. After the plants are well established, watering should be done thoroughly but not too often. It is advisable to irrigate seedlings in the morning and not in the afternoon as the latter leaves the soil surface moist overnight, a condition favoring damping off.
2.) Shading. Shading should be done to protect the young seedlings from high heat intensity in sunny areas and also from heavy rain. Shade can be provided by polythene nets or even grass. The shade should be removed some days before transplanting to allow the seedlings to acclimatize to field conditions.
3.) Thinning. This is a way of regulating plant density in rows and in holes. During thinning, weak, diseased plants are pulled out to allow healthy seedlings to grow well. It is normally done when seedlings have formed a few true leaves.
4.) Insect pest and disease control. This is a continuous process from seedling emergence to transplanting. It is normally done by physical means but chemicals can also be used if the need arises. 5.) Weeding. This is done by physical means when weeds emerge.
6.) Hardening-off. Transplants must be ‘hardened-off’ so that they can withstand the transition from a relatively sheltered and protected environment to a sometimes harsh open situation. Generally, hardening is imposed from about 1 to 2 weeks prior to transplanting seedlings, by gradually exposing them to higher (or lower) temperature and the higher light intensity prevailing in the field. It should, however, not involve any treatment that may reduce the rate of photosynthesis, such as nutrient stress. Care should be taken not to over-harden plants, as this may delay maturity and in some instances even reduce crop yields.
7.) Transplanting. This refers to the operation of lifting the seedlings from the seedbeds or containers and transferring them to the field where they will grow and mature. The main aim during transplanting should be to interrupt growth as little as possible, and if the operation is not carried out properly it can severely check growth or in extreme cases cause death of transplants.