Seed rate is the amount of seeds to be planted in a given unit area governed by ultimate crop stand which is desired. The objective of correct spacing of crop is to obtain the maximum yields from a unit area without sacrificing quality. Most crops are seeded at lighter rates under drier conditions than under wet or irrigated conditions.
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Seeds with low germination percentage are planted at higher rates than those which have about 100% germination percentage. There is an optimal seed rate for various crops. For example, the seed rate for maize is 22 kg per hectare, wheat is 110 kg per hectare and cotton is between 17 to 45 kg per hectare.
Factors to consider in choosing seed rates.
Seed purity.
When planting seed which is pure or with a high germination percentage, less seed is required. On the contrary, more seeds are required when using impure or mixed seeds.
Germination percentage.
Less seed is used when its germination percentage is higher. Seed of lower germination percentage is required in large amounts.
Spacing.
At closer spacing, more seeds are used than in a wider spacing.
Number of seeds per hole.
When two or more seeds are planted per hole, higher seed rate is required than when only one seed is planted per hole.
The purpose of the crop.
A crop to be used for silage making is spaced more closely than one meant for grain production. This would require use of more seeds. Maize to be used for silage making, for example, requires more seeds than that meant for production of grain.
Depth of planting.
This is the distance from the soil surface to where the seed is placed. The correct depth of planting is determined by:
Soil type: seeds will emerge from grater depths in sandy soil that are lighter than in clay soils.
Soil moisture content: it is recommended that one plants deep in dry soils in order to place the seeds in a zone with moist soil.
Size of the seed: Larger seeds are planted deeper in the soil because they have enough food reserves to make them shoot and emerge through the soil to the surface.
Type of germination: seeds with epigeal type of germination (carry cotyledons above the soil surface) such as beans, should be planted shallower than those with hypogeal type of germination (leave cotyledons under the soil) such as maize.
Suggested activities.
- Learners to carry out planting using broadcasting method and planting rows.
- Learners to identify different vegetative propagation materials displayed by the teacher.
- Learners to determine the correct plant population for a given area by mathematical calculations.
- Learners to collect samples of different tree seeds and prepare them for planting by various methods of breaking seed dormancy.
- 5. Learners to determine the germination percentage of different samples of cereals and legume seeds
See also
CLASSIFICATION OF ANIMAL FEEDS