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Tomatoes: compost, manure and a disease-wise plan.
Tomatoes are a high-value crop and a hungry one. Well-made manure and compost give them steady food and better soil, but tomatoes are also prone to bacterial wilt, blight and blossom-end rot. Most of what protects the crop is rotation, clean seedlings, steady watering and hygiene.
The numbers that matter
These figures come from the Ministry of Agriculture’s SHEP PLUS tomato production guide. Rates are per acre, as farmers use them.
Start with the right place and clean seedlings
Site and soil
- Tomatoes grow from sea level to about 2,000 m, where rainfall is above 600 mm a year.
- They like day temperatures of 20 to 25°C and night temperatures of 15 to 17°C.
- Choose well-drained sandy, loam or clay loam soil with a pH of 6.0 to 7.5.
- Have the soil tested. The guide says fertiliser type and amount depend on the results.
Nursery
- Use about 40 to 75 g of seed per acre.
- Pick a well-drained plot that has had no Solanaceae crops for three years.
- Make beds 1 m wide with drills 10 to 20 cm apart. Sow thinly and cover lightly.
- Harden seedlings for 1 to 2 weeks by easing off watering and exposing them to sun.
- Protect against whiteflies, which spread viruses, with insect-proof netting.
Transplanting and spacing
Transplant 30 to 45 days after sowing, in the early morning or late evening. Space rows 75 to 100 cm apart and plants 40 to 60 cm apart, depending on variety. That is roughly 6,700 to 13,300 plants per acre.
SOURCE: MOALF/SHEP PLUS, TOMATO PRODUCTION GUIDE
Manure, compost and fertiliser
- In the planting holePut two to three handfuls of well-decomposed manure or compost in each hole. The guide equates this to about 8 tonnes per acre (roughly 20 t per hectare, our conversion). It gives no separate rate or timing for compost.
- Basal phosphorusAdd 10 g of TSP (two bottle tops) to each hole. That works out to about 80 kg per acre.
- First top dressingFour weeks after transplanting, apply 40 kg per acre of CAN as a circular band around each stem.
- Second top dressingFour weeks later (eight weeks after transplanting), apply 80 kg per acre of CAN in the same way.
Potassium and calcium.
The guide mentions MOP for potassium and calcium products, such as lime on calcium-poor soil, but gives no rates for either. A soil test is the way to decide. We have not invented figures.
SOURCE: MOALF/SHEP PLUS, TOMATO PRODUCTION GUIDE. HECTARE FIGURE CONVERTED FROM ACRES.
Water, staking and hygiene
- Water carefully. Water matters most right after transplanting and during flowering and fruiting. Furrow or drip irrigation is preferred, and overhead irrigation spreads disease. Drain a waterlogged field within one to three days.
- Stake tall varieties. Indeterminate varieties need staking or training and pruning of side shoots. Determinate varieties need no staking, though staking or mulching helps in the wet season.
- Sterilise your blades. Dip pruning knives in a 1:1 mix of chlorine bleach and water to avoid spreading mosaic virus and bacterial wilt.
SOURCE: MOALF/SHEP PLUS, TOMATO PRODUCTION GUIDE
Common problems and what the guide advises
| Problem | What to do |
|---|---|
| Bacterial wilt | Remove wilted plants together with the soil around the roots and destroy them. Rotate with cereals, solarise beds and sterilise tools. |
| Late blight | Rotate crops, remove volunteer plants, and prune and stake for airflow. Use registered fungicides, and check the current list with the Pest Control Products Board. |
| Blossom-end rot (dark, sunken patches at the base of the fruit) | Keep soil moisture steady while fruit develops, lime calcium-poor soil, avoid excess nitrogen, mulch, and consider a calcium spray. |
| Fusarium wilt | Use resistant varieties and certified seed. Avoid seedbeds on infected land. On acid soil, raise the pH with lime or farmyard manure, and avoid too much nitrogen. |
Keep diseased plants out of the compost heap.
The guide says to destroy wilted plants, not to compost them. Follow that, and rotate with cereals.
Can manure and compost help against wilt?
An Ethiopian study mixed amendments into topsoil at 1, 5 and 10 percent and then added the wilt bacterium. Farmyard manure compost at 5 and 10 percent suppressed the bacterium completely, and 10 percent gave the best growth. One green compost treatment did worse than doing nothing, so not every compost helps. The abstract did not report exact incidence figures or say whether the work was done in pots or in the field, so treat it as encouraging rather than proven for your farm.
SOURCES: MOALF/SHEP PLUS, TOMATO PRODUCTION GUIDE; “EFFECTS OF DIFFERENT SOIL AMENDMENTS ON BACTERIAL WILT CAUSED BY RALSTONIA SOLANACEARUM AND ON THE YIELD OF TOMATO” (ETHIOPIA), SIPAV ARCHIVE
Picking and handling
Pick in the early morning, keep the fruit cool and shaded, and grade it by ripeness. Time to harvest depends on the variety and conditions. The guide’s variety tables give about 75 days after transplanting, while its harvest section says three to four months, so check the variety you plant.
SOURCE: MOALF/SHEP PLUS, TOMATO PRODUCTION GUIDE
Questions people ask
Is compost enough for tomatoes?
The Ministry’s guide recommends manure in the hole together with TSP and two CAN top dressings. It does not give an all-organic programme. Compost improves the soil, but check with an extension officer before dropping fertiliser entirely.
Can I use fresh manure?
Use well-decomposed manure or compost. Fresh manure can carry pathogens. See the food-safety rules.
What should I plant after tomatoes?
Cereals such as maize, according to the guide’s advice for bacterial wilt. Avoid potatoes, peppers, chillies and eggplant, which share the same diseases.
Why do my fruits have black patches at the base?
That is blossom-end rot, linked to calcium and uneven watering. Water steadily, mulch, avoid too much nitrogen and test whether the soil needs lime.
Should I grow tomatoes after potatoes?
Not if you can help it. They are in the same family and share bacterial wilt and blight. Follow the rotation rules above.
Growing tomatoes for the market?
We help growers build soil, set up composting and plan rotations that cut disease losses.