Mellen Nyabuto
For most farmers, getting access to clean planting material (healthy seedlings) is a great challenge. The health state of the seedlings before transplanting is very key. A healthy seedling is highly likely to have a higher survival rate, produce more and be less affected by pest and diseases. For most farmers in Kenya they either develop their own seedlings or buy seedlings from seedling producers for crops that can be transplanted. Examples of crops that can be developed into seedlings for transplanting include: most vegetables such as the brassica family, spinach, onions, tomatoes, fruit trees such as paw paw, avocado, passion, mango e.tc.
The conventional way for seedling propagation in Kenya for most farmers is through soil seed bed (seed nurseries) propagation. This involves preparation of a small portion of the land in which the seeds can be sown for germination. For most crops, it takes about 3-4 weeks for the seedlings to develop. After the period the seedlings can then be transplanted to a bigger portion of land with the aim of attaining a harvest. Another common way of developing seedlings, is through the greenhouse seedling propagation method. In this case the seedlings are developed in controlled conditions i.e. temperature, water and nutrients. Contrary to the conventional way, this method uses soil-less media as the medium of growth. The soil-less media is put into sizeable planting trays and the seedlings are sowed singly and allowed to germinate under greenhouse conditions. The media provides an environment likened to that of soil for the seed to germinate and develop. During the seed developing period, watering and nutrient application is done. The trays provide space for each seedling root to grow and develop. These seedlings have an advantage since the root system is not interfered with during transplanting. The roots remain intact, shielding the plant from transplanting shock. Transplanting shock causes the growth and development of the seedlings to temporarily stagnate which will eventually affect the yield. Some of the examples of the soil-less medias that can be used include; peat moss, pumice, sawdust, vermiculite and coco peat. Some of this soil-less Media can be obtained in ready-made form from companies such as ocean agriculture or organic fertilizer companies. Depending on the choice of media some may require prior treatment to bring the electrical conductivity (E.C), the pH to the required level and also to remove unwanted salts. Electrical Conductivity is the ability of the media to allow the plant to absorb nutrients. The E.C values should be 1.6-2.0 while the required pH should be 5.5-6.5. Below are some of the merits of developing seedlings via soilless media.
Benefits of using soilless media include:
- The media provides a disease free environment for the seedlings to germinate
- Germination percentage is higher
- Reduces seedling mortality rate.
- Uniform germination rate
- Easy to carry out management practices.
- Root system of seedlings is robust and intact eliminating effects of transplanting shock.
Besides being a healthier way of seedling production, this kind of propagation can also be a lucrative source of income and employment. However this type of propagation system will require the farmer to have most preferably a greenhouse structure or good shed structure.
Below are the steps that can be followed in order to develop seedlings in soilless media in a greenhouse seedling propagation unit.
- Preparation of materials
This is the first stage in the seedling propagation unit and it involves assembling of all materials needed, details of seeds to be sowed and media treatment.
Materials that may be needed may include seedling trays, water, and calcium nitrate as treating agent for coco peat media .Coco Peat is the most preferred media since it’s affordable and easily accessible. However when purchasing this media the farmer should be keen to inquire whether it’s treated or not .Using untreated coco peat can result to poor germination, scorching effects, and stunting in plants leading to losses. Below is a step by step procedure a farmer can follow to
Treat untreated coco peat.
- Soak the coco peat in water.
Soaking the coco peat loosens it and hydrates it.This can be done up to for 15minutes.
- Adding calcium nitrate
For every five kilograms of coco peat one can use up to a spoonful of calcium nitrate. Stir the mixture well and leave for 24 hours. Calcium nitrate displaces the unwanted salts in the media.
- Wash the coco peat severally with clean water.
After the 24 hours, wash the coco peat draining the water .The mixture can be washed 6-7 times to remove any remains of unwanted salts.
- Measure the electrical conductivity (E.C) using an E.C meter and pH of the media using pH meter.
The E.C should be 1.6-2.0 and pH of 5.5-6.5.
- Loading the seedling trays with the media.
Put the media on the tray and make small holes for the sowing the seeds.
- Sowing on trays
Plant the seeds on media in the holes made in the media. Ensure to cover the seeds using the coco peat media.
- Labelling
Once you’ve sowed, remember to label your trays for easier identification. Information such as date of sowing, crop, variety, and quantity can be included in the labelling.
- Put them in germination Chamber/growth room.
Germination chambers are mostly used by growers to reduce germination time, enhance uniformity, and increase germination rate by providing conducive conditions. Conditions necessary for germination include moisture, light, temperature and Oxygen. The duration in the chamber will depend on the type of crop, some can take up to 3 days in the chamber .The trays can then be moved to the greenhouse set up.
- Greenhouse.
Transfer the seedling trays into the greenhouse set up. This is to allow the sprouted seedlings to germinate to maturity. Inside the screen house the trays should be placed on raised wood or mesh beds. The seedlings are maintained by watering daily and nutrient supply. This can be done using a simple watering can. When watering the pressure should be kept low to prevent disturbing and splashing of the media. This maintenance should be done until they are ready for transplanting.
- Crop protection in the greenhouse.
It’s is highly recommended that the greenhouse is kept free of diseases and pests. Most common encountered pests and diseases are thrips, white flies, and tutor, and bacterial wilt, viral and fungal diseases in the greenhouse. Use of tutor traps, yellow sticky traps and Blue sticky traps can be used to manage most of the pests. Bio pesticides and bio fungicides can be sprayed regularly to manage fungal and bacterial invasions. It’s important to observe and maintain sanitary rules while in the greenhouse to reduce the pests and disease occurrences.
Once the seedlings have matured, they can now be transferred to be transplanted in the soil. Most greenhouse seedling propagators raise the seedlings for commercial basis. They sell to farmers who then plant them. Farmers can easily access the seedlings from this propagators from their propagation units. For this commercial purposes, the propagation unit has to be registered and certified by the Kenya Plant Health Inspectorate Service (KEPHIS).
Mellen Nyaboke is a plant pathologist at International Institute of Tropical Agriculture.
Email: mellennya96@gmail.com