Proper Seed Sowing and Planting Practices Guide
Time of Seed Sowing or Planting: Several factors influence the time of sowing or planting. They are: rainfall, temperature, day length, occurrence of diseases and pests, marketing, cropping system and availability of labour and equipment.
1. Rainfall
Rainfall or the availability of moisture is one of the principal factors which determine when a crop should be planted.
On a seasonal basis, the crop should be planted at a time when there will be enough subsequent rainfall to see it to maturity or full establishment.
For this reason, the planting of long season annual crop such as yams must occur at the beginning of the rainy season so that the crop has the entire rainy season available to it for development.
For perennials crops such as cassava, cocoa and rubber, planting in the field early in the rainy season is also advisable so that the crop can become established before the dry season sets in.
For short-season annuals such as cowpeas, sweet potatoes and maize, planting may be delayed till later in the rainy season, as long as the crop can complete its growth and development before the onset of the dry season.
Sometimes the intention is to let the maturity period correspond with a rainless period. For example, the sowing of cowpeas or millet is often timed so that the crop matures during a dry period.
Planting should normally be done in moist soil to allow for rapid seed germination or sprouting of the vegetative propagule. For this reason, planting is normally done within a few days after rain.
2. Temperature
Temperature is another climatic factor that influences the time of planting. In the temperate regions, this aspect is crucial, but in the tropics it assumes appreciable importance only at high altitudes, where planting should be done when the soil is warm enough to permit rapid germination.
In other parts of the tropics, especially in the drier regions, excessively high temperatures may adversely affect seedling emergence.
3. Day length
Day length or photoperiod is a third factor that may influence the time of planting. The crop should normally be planted at a time that would permit the appropriate photoperiod to exist at the flowering or tubering stage.
For example, some okro varieties which require short days for flowering will remain vegetative for most of the rainy season while long day conditions persist.
The planting of such varieties could conveniently be delayed so that short-day conditions for flowering exist shortly after the plants are fully established.
4. Occurrence of Diseases and Pests
The occurrence of diseases and pests may influence the time of planting. The strategy is usually to adjust the time of planting so that the crop is on the field during the time when its diseases and pests are least prevalent.
Cowpea production in southern Nigeria, for example, has been strongly influenced by this factor.
Cowpeas sown in the early part of the rainy season are bedeviled by numerous diseases and pests but if sowing is delayed until the latter half of the rainy season, the incidence of diseases and pests is less severe and a decent yield can be obtained.
5. Marketing
Marketing consideration may also influence the time of planting. Planting is timed so that harvesting occurs when the crop can command a good market price. This is particularly true of vegetables and other crops which cannot be stored for long.
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6. Cropping system
The place of a crop in a rotation or in an intercropping system may determine at what time of the cropping cycle it is planted. For example, many intercroppers usually plant their cassava in the latter part of the rainy season after some of the earlier intercrops such as maize; okra and melon have been harvested.
The cassava could have been planted earlier, but it is made to wait until the harvesting of the earlier intercrops creates enough space between the yam plants.
Availability of Labour and Equipment
The availability of labour, equipment and processing facilities are other factors that may influence the time of planting.
Methods of Seed Planting or Seed sowing
Planting of field crops is generally carried out by any of the following methods of planting: Broadcasting, Drilling, Precision planting, and Transplanting.
1. Broadcasting
This is a deliberate random scattering of seeds on the field or prepared seed bed. There is no specific or definite inter or intra-row spacing of crops observed. Crops commonly planted by this method include rice, wheat, sesame and some vegetables.
2. Drilling method
In this method, seeds are placed in shallow furrows created with disc or hoe and then buried. The spacing between plants may not be regulated. Many field crops are planted using this method.
3. Precision planting
Cereal crops such as maize, sorghum and millet are planted with a definite inter and intra row spacing to achieve a precise plant density. This method ensures maximum productivity and high yield of crops.
4. Transplanting
Some crops are first raised in the nursery and later transplanted into the permanent field where they mature and complete their growth cycle. Seeds of tobacco, tomato, pepper, and many vegetables are first raised in the nursery before transferred to the field.
Rice and sorghum are also transplanted in some instances. Transplanting has the advantage of reducing wastages of seeds and offers farmers the chance to transplant only healthy and vigorous seedling for best results.
Factors determining the choice of planting methods include the following: Seed size, Growth habit of the plant, Seedbed preparation, Climatic condition, Labour availability, and Seed placement in the field.
There are four general aspects to seed placement in the field:
The number of seeds sown at each spot stand.
The spacing between stands.
The depth to which seeds are placed.
The position of the seed with respect to the previous tillage operations i.e. whether the seed is sown on the ridge or mound, in the furrow, on the slopes of the ridge, or on the flat.
Number of Seeds per Stand
The number of seeds sown per stand depends on the expected percentage germination of the seed and number of plants desired per stand. The expected percentage germination is ascertained by prior germination tests and if low, the number of seeds sown per stand is commensurately increased.
Sometimes the number of seeds sown on each stand is kept deliberately high, so that the number of plants appearing on each stand is higher than the desired number.
When the seedlings are well established, the extra plants are removed, leaving just the desired number per stand. This procedure of removing excess emerged seedlings is referred to as thinning.
The main advantages of deliberate over-seeding and subsequent thinning are that:
It provides the opportunity to select out weak seedlings.
It ensures the retaining the vigorous ones.
It ensures that every stand has the correct number of seedlings.
Spacing between Stands
The spacing between stands is largely determined by the extent of the root and shoots system of the crop plant in question.
The spacing determines the size of the land area available to each plant or stand and the larger the plant the greater the area required for it to performed well. The spacing between the crop rows is usually adjusted to what mechanical planters can cope with.
Sometimes sowing is done by scattering the seeds at random on the field or plot. This method of sowing is referred to as broadcasting. Broadcasting is most commonly used to sow small seeds such as rice on the field or vegetable seeds in the nursery.
A slightly different method of sowing seed is drilling in which the seeds are sown in a continuous band in rows. As such, the space between the rows is fixed and can be determined, but the spacing within the row is indeterminate.
The spacing between stands determines the number of stands per hectare. The number of stands per hectare and the number of plants per stand together determine the plants per hectare, or the plant density.
Depth of Sowing Seeds
The depth at which the seed is placed in the soil is influenced by: seed size, type of germination, moisture status of the soil, and soil type.
1. Seed size
The larger the seed, the greater the depth from which it can emerge and the deeper it can be safely sown. This is because large seeds have ample quantities of stored food material for the germination process.
As such, they produce vigorous seedlings which have enough stored food for the long time it may take to emerge from great depths. Small seeds, on the other hand, tend to deplete their stored food in a short time.
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