| The bio-intensive approach to small-scale household food production |
|Seed and seedling management|
Seed comes from the flower. The flowering and seeding are affected by the health of the plant and its surroundings or environment. Seed quality is also affected by the parent plant.
I. Environmental Factors that Affect Seed Production
Photoperiodism refers to the flowering response of a plant to the length of day, or more precisely, the length of the light and dark periods.
1. Short-day plants flower and bear fruit juring the months where the nights are long and the days are short. In the Philippines, short-day periods occur during the months of. September to February.
Example: most soybean varieties, winged bean, hyacinth bean, lima bean, pigeon pea
2. Long-day plants flower and bear fruit during the months wherein the nights are short and the days are long. In the Philippines, long-day periods occur during the months of March to August.
Example: onion, sunflower
3. Day-neutral plants flower and bear fruit all year round.
Example: yardlong bean, ladyfinger, cowpea
Depending on the variety, some plants, like soybean, can either be short-day, long-day or dayneutral.
Temperature has a direct effect on flowering and seed production.
1. Tropical plants -- These are plants that flower and produce seeds in hot or tropical areas. Most of these plants flower and produce seeds in the Philippines.
Example: tomato, pepper, cowpea, ladyfinger
2. Temperate plants -- These are plants that flower and produce seeds in cold or temperate areas. Most of these plants flower and produce seeds in cold areas in the Philippines, like Baguio and Tagaytay.
Example: pea, cabbage, pechay, radish, onion, carrot, cauliflower
In areas where the temperature is not cold, temperate plants can be induced to flower and produce seeds if they are placed in cool conditions before planting. This method is called vernalization. Vernalization is done by soaking the seeds in water and placing them (after the radicle or rudimentary root has protruded) or their plant parts (example: onion bulb, tuber of carrot) in a cold (but not freezing) place like a refrigerator.
No. of days inside the refrigerator
30 - 90
40 - 50
tuber of carrot
14 - 56
4 - 8
5 - 7
5 - 7
The right amount of water is needed for the growth of the plant. Hard and continuous rain is not good for seed production since:
1. pollen is not transferred;
2. seeds do not develop from flowers;
3. the vegetative stage of the plant or the maturity of the fruit/seed is prolonged;
4. seeds germinate even if it is still not harvested from the plant;
5. harvesting becomes more laborious;
6. pests attack or infest the plants; and,
7. seed yield decreases.
To prevent seed production during the rainy periods, plants can be spaced at wider or longer distances so that all the plants can have enough sunlight.
On the other hand, lack of rain or water is not good for the plant since it will prevent the normal growth of the plant and the plant may not produce flowers and seeds. Even if flowering occurs, the quality of the seeds is not good and the the seed yield is low.
The strength and direction of the wind affect the pollination of flowers.
To produce good seeds, the soil must be healthy and fertile. The right pH (acidity of the soil) for a specific plant should also be obtained.
II. Cultural Practices
A. Timing of Planting
Plant seeds when the weather is good. Usually, seeds are planted during the rainy season in order to have continuous amount of water. It is good to transplant early in the morning or late in the afternoon.
B. Planting Distance and Rate of Planting
The distance between plants used for seed production is wider compared to that of plants used for other purposes (example: vegetable production, fodder production). More seeds need to be planted if the broadcast or sowing method is done. The distance of planting is also wider if the soil is not fertile and in the rainy season. Widening the distance will enable plants to receive enough sunlight.
C. Hastening Seed Germination
1. Seed Cleaning or Seed Washing -- Soak the seeds in a container of water and remove the seeds that float. Seeds which float have poor quality.
2. Use of Inoculants -- Some microorganisms help in good growth of seeds. Rhizobium (a kind of bacteria) gets nitrogen from air and gives the nitrogen to the plant and soil. This is usually used for legumes. Mychorrhiza (a kind of fungus) helps the root absorb elements like phosphorus from parts of the soil that cannot be reached by the root. This has been found effective in corn and different vegetables. The two inoculants can be used to Minimize the use of fertilizer.
3. Seed Scarification -- This method is appropriate to seeds (example: winged bean, bitter gourd, sponge gourd) that are hard and difficult for water and air to penetrate. This is done by (1) nicking off the seed coat with a knife or nailcutter, (2) puncturing the seed coat with a needle; and, (3) rubbing the seeds in sandpaper, file or any rough material. Care should be done so as not to injure the internal portion of the seeds, especially the radicle.
4. Hot Water Treatment -- Pour hot water (boiled and then cooled for about 10 - 15 minutes) into a container with seed (10 parts water to 1 part seed). Let stand for 3 -10 minutes or until water cools off. Seeds may be left soaking overnight. Old seeds are soaked for a shorter time than new seeds.
5. Soaking Seeds in Ordinary Water Overnight -- Soak seeds in tap water for 1248 hours (depending on the species). This method is not recommended for all seeds, especially seeds that quickly absorb water like most legumes.
D. Maintaining Seed Purity
The following methods are important to prevent contaminating other plant varieties from the variety that is being grown.
1. Planting distance -- The plant being grown should be kept at a distance from other varieties and also from plants that are of the same family. Varieties of cross-pollinated plants should be planted at greater distances from each other than self-pollinated plants. For self-pollinated plants, the planting distance should not be less than 10 meters. For cross-pollinated plants, the planting distance should not be less than 100 meters.
2. Planting timing -- Avoid planting at the same time plants from the same family or of different varieties of the same species. This ensures that they will not flower at the same time.
3. Use of Windbreaks -Choose an area where there are tall plants in between plants of the same family or species.
4. Border Rows -- Rows of plants of the same variety as the plants being used for seed production, planted on the edges of the plot. Seeds from the plants in the border rows are not used for planting.
5. Roguing -- Roguing is done by pulling out plants that are: (1) off-types (plants with different color, shape, etc.); (2) diseased or insect-damaged; and, (3) of different varieties. Failure to remove off-types results in poor quality seeds since off-types might cross-pollinate with good plants.
6. Bagging and Caging -- This prevents pollination of plants that are of different species and variety.
Proper care and the right nutrition should be given to the plant to have good and high seed-yield. Organic fertilizers are recommended.
The amount and frequency of watering should be adjusted for good seed-yield. Plants need less water after flowering than during the vegetative stage.
G. Pest and Disease Management
Pests and diseases affect the quality and quantity of seed yield. To prevent infestation of pests and diseases, cultural practices like intercropping, mixed or multiple cropping and crop rotation are recommended.
Botanical pesticides can also be used to prevent infestation of pests and diseases. If some plants already have disease, pull them out and burn or bury them underground to prevent contaminating other plants.
Use of good quality seeds (seeds with good germination percentage and without seedborne pests and diseases) can also prevent pest and disease infestation.
Another way of controlling pest and disease infestation is to use traditional seeds.