Tomato is propagated from seed. The seedlings are mainly raised in a nursery before transplanting. However, direct planting can be done at a rate of 500g/ha. The nursery would require 100g /ha pure germinating seed. Handling of the seeds and seedlings influences the growth and yield potential of the crop. The variety selected is dependent on the farmer requirements which include high yielding resistance to diseases, market preference, keeping quality after harvest, processing or fresh market, open field or greenhouse/high tunnel.
Tomatoes can be grown in a range of altitude from 0- 2000m a. s. l. The temperature range is between 18oC to 30oc but the preferred is 20-25oC. Rainfall/water requirements are such that it should have at least 600mm durum the growing period. The soils should be well drained with adequate organic matter and a pH of 6 – 6.5.
Site selection and land preparation: Land that has had no solanaceous crop grown for at least three consecutive seasons. The land should be prepared to fine tilth, early enough to allow for weeds and soil dwelling pests to die.
Plough a depth of about 16-20cm and remove all weeds or any crop debris that may carry over pests and diseases. This is the time that manure can be ploughed in at 40tons/ha.
Plough and raise beds at least 15cm above mixing the soil with well rotten manure at 5kg/m2 and basal planting fertilizer either SSP at 4 Kg/m2 or DSP/ DAP at 2Kg/m2.
The land should have no chemicals nor fertilizers applied. Instead double dig (30 -45 cm deep) and add manure at a rate of 60 tons /ha.
Open field varieties:
Rio Grande, Roma, Cal-J, Beauty, Money maker, Heinz M 82, Hundred set, Marglobe; Hybrids: Kentom F1, Zawadi F1, Eden F1, Fortune maker F1, Tanzanite F1, Unique F1, Monyala F1,
Green house varieties:
Eva, Anna F1, Tylka F1, Kilele F1, Bravo F1, Bingwa F1, Proster F1, Libra F1, Chonto, Milele F1
Note: one variety cannot satisfy all the farmers desires and hence the need for a compromise.
The seeds can be planted in seedling trays whose wells carry an appropriate media enriched with nutrients such as coco pit. These require planting within the three weeks’ mark after germination. Beyond this point the wells start limiting the root growth and hence the yield potential of the variety selected. The other alternative, is to select a site shaded or protected from direct sunlight, near a water source. The site should have soils that are well drained. The area should be ploughed and the nursery bed raised 15 cm high. The nursery should measure 1m wide and 6m long depending on the area that is to be planted. The soil should be mixed with manure at the rate of 5Kg/m2. Along the seed drill lines, a basal planting fertilizer should be applied at 40g/m length for SSP and 20g/m length of DSP or DAP. The seed drill line should be spaced 15 -20 cm apart. During seed drilling mix the seed with dry sand at a ratio at a ratio of 1:3. or literally place each seed about 4-5 cm apart for the high value seed, Cover with grass and water regularly. 1 week after germination remove the grass mulch and replace with a shade frame raised 1 m above the seedlings. This will protect the seed and will also regulated the amount and impact of water on seeds during the watering. The seedlings should be ready for planting at 3-4 weeks after germination at a height of 15- 20cm or when they have 3-5 true leaves. Harden the seedlings before transplanting by reducing the amount of water applied and removing the shade to expose to the sun.
Before transplanting the field or the beds should be thoroughly watered. Select the healthy and vigorous seedlings for planting to obtain a uniform stand. The seedlings should be placed at the same depth as they were in the nursery and the planting should be done late in the evening. The spacing is dependent on the purpose of growing the tomato (processing versus fresh market fruits) and where the crop is grown (open field versus high tunnel). For processing the spacing is 60 by 45-60 cm, for fresh market the spacing is 60-90 by 60 cm; and for greenhouse the spacing is 60 by 60 cm were the seedlings are alternated on the raised bed. (plant population should range from 18, 520 for wider spacing to 27, 778 plants /ha for closer spacing). After placing the seedlings in the planting holes, the field should be irrigated once more.
Fertilizers and manures:
Where these were not ploughed/incorporated into the soil during land preparation, during transplanting: Manure should be applied at 5 kg/ 1.2 m2 or 9 planting holes at 60 by 60 cm. The manure and fertilizer should be well mixed with the soil before placing the seedlings.
Fertilizers: Add 400 kg/Ha SSP (21% P2O5) or 14g/planting hole; or 200 Kg DSP or DAP or 7g/planting hole. Top dress with 100 Kg/ha of CAN (26% N) or 3-4 g/ plant when the seedlings are 25 cm high or 2-3 weeks after transplanting. Add another 200kg/ha of CAN or 7-8 g/plant 6 weeks after transplanting as the first flowers start appearing.
Apply enough water to recharge the rooting zone. In greenhouses drip irrigation is used and plants utilize 300 to 500 ml/plant/ day depending on the weather conditions or where the crop is grown.
Pinch the side shoots to leave one or two main stems. Continuously remove the side shoots and any leaves that may be touching the soils.
In the field use strong (1 -1.5-inch-thick) supporting sticks about 2 m high which will be used to train the plant or build a support structure with poles onto which wires a weaved and used to support the plants. When the plants produce 6-8 flowers, the growth point of the plant should be pinched to allow the fruits to grow into good size. In greenhouses, the hybrids are indeterminate hence will need a well erected supporting structure that will withstand the weight of the plant and its produce.
This should be done regularly to avoid competition or act as hosts of pests and diseases.
This is done to control soil temperature, conserve water, reduce weed pressure and to control pests such as mites which thrive in dry and dust areas, thrips and leaf miners that pupate in the soil.
Pests and diseases:
Tomato is prone to many pests and diseases that reduce the yield if not managed well. Integrated pest management offers an option where pesticide applications are reduced substantially. Hence the need to have some form of monitoring by use of traps yellow, blue and walking in the field or greenhouse to observe how the plants are doing.
Common pests and diseases:
Late blight, early blight, Fusarium wilt, Bacteria wilt, Bacteria canker, Root knot nematodes, viruses
Arthropods: Mites, whitefly, American leaf miner (Tuta), Bollworm, aphids, thrips and vegetable leaf miner
The crop matures from 3-4 months after germination. Fruits for processing should be harvested when fully ripe while those of the fresh market can be harvested from green ripe when they are starting to turn color to firm ripe. They should be harvested and kept in a cool /shaded area where they are sorted into small, medium and large, as well as firm green or ripe. Transport to market using wooden or plastic crates.