Complete Guide to Open Field Tomato Farming

The tomato, once considered to be highly poisonous, is a widely used vegetable in cooking around the world. 

With consistent market demand, both for fresh tomatoes and processed tomato products, farming tomatoes can be a profitable venture. To achieve success, you will need to be well equipped to deal with the management, production, and marketing challenges that are faced by tomato farmers. 

In this comprehensive guide to tomato farming, we will take you through the required practices from tomato seedling to post-harvest handling of tomatoes. This will equip you to deal with the challenges and ensure your tomato farming enterprise is profitable. 

History of the Tomato

Native to Mexico, and introduced to Europe in the 16th century, the tomato traditionally had a mixed reputation. 

In Europe, when plates for rich people were made out of pewter (lead), the acid in tomatoes would react with the lead, resulting in lead poisoning and eventual death. This was not so for poor people, whose plates were made from wood. This made the tomato only a preserve of the poor. 

When it comes to tax avoidance, the tomato was classified as a fruit, so as to avoid the high taxes that were imposed on vegetables. It took a supreme court ruling to overturn this classification, to the much annoyance of botanists, who scientifically classify the tomato as a fruit. 

Talking about good coming from a bad family, the tomato belongs to the nightshade (Solanaceae) family of plants, where some members are known to be highly poisonous. 

Admired only for its beauty, the tomato was thought to be poisonous and was not consumed as food.  The tomato was rumoured as an essential item in witchcraft and as an aphrodisiac. You can see now why no one wanted to consume tomatoes as food. 

Tomatine, a poisonous substance is present in the leaves of tomato plants.  In the tomato fruit, tomatine is available in its non-toxic form. It would take huge amounts of tomatoes to actually poison someone, but the research of animals especially dogs shows negative effects in their nervous and digestive system. 

Therefore you can consume tomatoes without worrying about poisoning, witchcraft and it giving you an aphrodisiac high. 

The tomato in modern times has become one of the most famous ingredients in food. In Fact some food, for example, pizza, would not exist without tomatoes.   

The tomato is one of the most processed agricultural products in the world, with worldwide production exceeding 70 million metric tonnes.  

Health Benefits of Tomatoes

The tomato fruit widely accepted globally and often mistaken to be a vegetable has a multitude of health benefits. 

The bright red fruit once believed to be poisonous to humans is packed with nutrients, vitamins, and other compounds beneficial to human health. Some of these benefits tomatoes have to offer include;

• Tomatoes are an excellent source of lycopene antioxidant, which aids the human body to rid itself of toxins that are harmful to us. Lycopene is also known to prevent prostate cancer.
• The fruit is full of vitamins such as vitamins A, C, and K, which are good for skin and immune health. The vitamins in tomatoes also help maintain healthy blood pressure, promote good eye health, and aid in collagen production for healthy hair, skin, and nails.
• Tomatoes are also suitable for expectant women as it contains folate that protects babies from the development of neural tube defects.
• Tomatoes also have a mineral called chromium, which helps keep blood sugar levels in check. Such minerals make tomatoes a healthy fruit for people with diabetes.
• The fruit is also good for your heart health. As much as it won’t fix broken hearts, vitamin A, vitamin B, and potassium in tomatoes aids in reducing cholesterol levels in the bloodstream, which clogs up arteries.

Tomato Varieties and their yields

There are categories of tomato varieties, namely determinate and indeterminate. 

• Determinate tomato varieties grow to a standard height of about 1metre. They stop growing when fruit starts forming on the top bud. The fruit from the plant ripens at approximately the same period (usually 7-14days). They stand on their own hence do not require staking for support.
• Indeterminate tomatoes continue growing and producing fruits until it withers due to environmental factors such as drought and frost. This variety reaches heights of up to 2metres. Indeterminate will flower, set new fruit and ripen fruit all at the same time throughout the season. They require substantial staking for support.

Some of the common varieties of tomatoes grown in Kenya include;

• Rio Grande– This is a determinate variety that does very well in warm climates. It is a very popular tomato with rich deep red and sweet-tasting fruits. Some of the attributes Rio Grande variety holds include;

1. It can yield up to 18tonnes per acre
2. The Rio Grande matures in between 75–85 days. 
3. It is tolerant to verticillium and fusarium wilt.

• Assila F1- This is a determinate variety that produces red coloured fruits with an oval shape and is known to be sweet. Other characteristics attributed to Assila F1 include;

1. Assila F1 is an early maturing variety taking 75days to mature after transplanting.
2. It is tolerant to Tomato Yellow Leaf Curl Virus and nematodes.
3. This variety can yield up to 23tonnes per acre.
4. It can be stored well and transported without much damage.

• Kilele f1 – This is a determinate variety suitable for growing in the drier or humid regions. Some of its attributes include;

1. This variety is tolerant to diseases such as Tomato Yellow Leaf Curl Virus, Tomato Mosaic Virus, Verticillium, Fusarium Wilt, and Nematodes.
2. It matures in 75-85days after transplanting.
3. Kilele F1 can yield up to 35tonnes per acre.
4. Its fruit is firm and elongated. The fruit has a 21day shelf life, thereby giving you adequate time to seek its market.

• Cal j – this is a determinate variety that is open-pollinated. It produces red, blocky shaped fruits. Some of the other attributes of this variety include;

1. It matures in about 75–85 days after transplanting.
2. This variety has the potential to yield up to 12tonnes per acre 
3. Cal J is also known for its easy transportability to the market

• Anna F1- Anna F1 falls in the category of indeterminate. It does well in both greenhouses and the open field. Some outstanding attributes for this variety include;

1. This variety matures in 75days. 
2. Anna F1 has a yield of about 74tonnes per acre. It can yield up to 35kgs of tomatoes per plant
3. Anna f1’s fruit is deep red, firm, and has an oval shape. 
4. This variety has a high resistance to Alternaria stem canker, Verticillium, Fusarium wilt as well as nematodes. 

• Prostar F1 – Prostar F1 is a hybrid indeterminate variety that does well in warm climates. It can be grown both outdoors or in a greenhouse. Some of its attributes include;

1. It takes between 80-85days to mature.
2. It can yield up to 180tonnes per acre.
3. This variety is tolerant to Leaf Curl Virus and Bacterial Wilt.
4. It has a long harvesting period and excellent keeping quality.

The choice of the variety that you should plant should be based on several factors that include;

1. The variety’s disease resistance capability. Some varieties are resistant to diseases such as fusarium wilt and nematodes.
2. Whether the variety is hybrid or the open-pollinated one. Hybrid varieties give higher yields but are costly in terms of the cost of seeds.
3. Depending on your farm, you should also consider whether the variety is determinate, indeterminate, or semi-determinate. Indeterminate varieties will raise your costs of materials and labour as you will be required to build the supports for the plants.
4. Also, the fruit type in terms of shape, size, and colour. The fruit type is determined by market needs, whether it is processing or market buyers.  

Ecological Requirements (Climate, rainfall/water/temperature/soils)

Tomatoes can grow in a variety of climatic conditions and soil characteristics. For optimal growth, tomatoes will require;

• Deep, well-drained soils. Tomatoes do well in a variety of soil types ranging from sand, loam to clay-loam soils that have a high content of organic matter.
• An altitude of below 2000metres above sea level.
• A Temperature of about 20 – 250C and optimal night temperatures of 15 – 170C. Extended periods of cold temperatures below 120C may lead to chilling injury, while temperatures above 270C considerably affect growth and fruit set.
• Well distributed rainfall of 600mm throughout the growing season

Land Preparation for Tomato Farming

Proper land preparation in tomato farming is key to healthy tomato plants and optimal yields. You should follow the following guidelines while preparing your land for tomato farming;

• You should plough the field to a fine tilth by giving one to two ploughing. Ploughing will encourage good drainage to prevent flooding during irrigation. A fine tilth is also essential for proper root development. 
• You should then open furrows in the recommended spacing if you intend to grow tomatoes in the field. 
• Pre-soaking your field by irrigating it two days before transplanting. Pre-soaking will ensure seedlings do not suffer from water stress. 
• Depending on the variety, dig up holes of 30cm with recommended spacing for either determinate or indeterminate varieties in preparation for transplanting. 
• Incorporate well-composted manure into the field to promote proper root development.

Nursery preparation and transplanting

Tomatoes do well when transplanted from a seedbed nursery as opposed to sowing the seed directly in the field. You should prepare a good nursery seedbed to ensure proper plant establishment and vigorous early growth.

Preparing your nursery is simple. You raise the bed around 15cm high and leave spaces for paths of around 30cm or more between the beds. Your row spacing should be around 15cm.

You should then thoroughly till the soil to make it easier for the small seeds to break through as they germinate. Do not bury the seeds deep into the soil.

You can use a stick to draw the lines in which you will plant the seeds and cover just slightly with soil and mulch to maintain excellent levels of moisture. Easy peasy!

In about 8-10 days, your seeds should start sprouting. You should then regularly water the nursery until a week or two before transplanting. Reducing your watering sessions will help harden the seedlings. 

Your seedlings will take about one month before they are ready for transplanting.

It is essential to keep on checking for pests and diseases to curb the spread of pests and diseases before it affects the whole batch in the nursery.

Transplanting Tomatoes

Transplanting should be done when seedlings are about 30cm high. This will be about 30 to 45 days after seed sowing.

Clear the field of weeds before planting. If the previous crop was in the tomato family, e.g. potatoes and eggplants, treat the soil for soil-borne insect pests and soil fusarium wilt. 

You should then plant the tomato seedlings at a spacing of 45cm by 60cms. Ensure you dig the planting holes to a depth of 15cm.

Pull the seedlings from the nursery bed after watering well to soften the soil. Watering reduces the risk of damaging the seedling while pulling it from the seedbed. Keep them in a shaded place. 

Plant the seedlings in each hole and cover the roots with soil firming the soil around the roots. 

Tomato Fertilizer requirements

Fertilizer plays a vital role in the development of excellent and healthy tomato plants. 

Before fertilizer application, you must carry out a soil test analysis on your farm to know the nutrients that are insufficient for the optimal growth of tomatoes.

Before transplanting in the holes you have prepared, apply 10 grams of DSP to each hole. Ten grams is about two bottle tops of the used soda bottles you’re hoarding under your kitchen sink. Ten grams per plant will translate to about 80kg per acre. 

If available, you can also apply manure at the rate of 8tonnes per (about two handfuls per each hole). 

Top Dressing Tomatoes

Tomatoes are top dressed in two phases;

• The first phase of topdressing should occur four weeks after transplanting. You should apply 5 grams of CAN (that is one bottle top) per plant. Five grams will translate to about 40kg per acre.
• The second phase of topdressing should be done 8weeks after transplanting. You should apply 10 grams of CAN per every plant (80kgs per acre).

Take your time and apply the fertilizer in a circular band around the stem. Hum along to some music while you feed your tomato plants. 

Failure to topdress or inadequate top dressing physiologically torture your plants leading to hollow cavities and poor taste due to potassium deficiency and blossom-end rot due to imbalance between nitrogen, calcium, and soil moisture. 

Irrigation Requirements for Tomatoes

Tomatoes are susceptible to water stress in the following two stages;

1. Immediately after transplanting. 
2. Flowering and fruit development stages.

Drip irrigation is usually the best-preferred method to water your tomatoes as it delivers water directly to the roots. Irrigation methods such as overhead irrigation encourage the spread of diseases such as early blight.

Be careful not to flood your tomato fields as they deprive the roots of air, leading to the death of the tomato plants.

Diseases affecting tomatoes

Tomato diseases can result in considerable losses in terms of the quality and quantity of your produce.

It is crucial to quickly identify any disease attacks and mitigate them before the disease spreads all over your farm. Some of the diseases that attack tomatoes include;

1. Fusarium wilt– this is a fungal disease that is spread by infected seeds and soil. It can survive on the soil indefinitely and is most active at temperatures of between 25-320C. It is characterized by;

• The lower leaves of the plant usually change from green to yellowish and wither off.
• Smaller leaves on one side may be affected while those on the other side are without any symptoms.
• When affected stems are cut, they display a red to brown discolouration of the xylem.

You can control this disease by using varieties that are resistant to fusarium wilt. Also, you should use certified disease-free seeds. 

You should also increase the soil pH by adding lime or manure if the soil on your farm is acidic.

2. Blossom-end rot– this is a physiological condition caused by calcium nitrogen imbalance in the soil, especially when the moisture level in the soil is low. It is characterized by;

• The fruit rotting at the blossom-end of the fruit. 
• The surface of the fruit becomes dark brown and sunken.

To control this disease, you must maintain adequate soil moisture at the fruit development stages. 

Also, you can lime your soils in case of calcium deficiency. You can as well spray your crop with calcium chloride to boost calcium levels in your farm.

3. Tomato Mosaic virus– This is a viral disease transmitted by infected seed and plant debris in the soil. You can also unknowingly transmit this disease through contaminated farming tools. This disease is characterized by;

• The shape of young leaves become distorted
• The tomato fruits will start to brown internally when they get infected at the mature green stage.
• Leaves start to mottle with raised dark green areas.

To control this disease, you should use only certified-disease free seeds. If you are a tobacco smoker (you should stop by the way), avoid handling cigarettes while handling your tomato plants as the disease can spread even from processed tobacco.

4. Bacterial wilt– This is a bacterial disease that spreads through infected soil. It can be transmitted easily by runoff water from infested soil.  It is characterized by;

• Water with a dark appearance oozes when a cross-section of the stem of a wilted plant is cut open.
• The plant will rapidly wilt and die without the yellowing of the leaves.
• A greyish slime will ooze when you squeeze the stem of a wilted plant.

To control this disease, you should practice crop rotation with plants that are not part of the nightshade family. You can also do spot treatment of infected plants by spraying infected plants with sodium hypochlorite 10% (simply JIK) or use lime or ash. You can also use available chemicals such as Metam sodium to tame the spread.

Pests affecting Tomatoes

Pests cause a lot of losses in terms of quality and quantity of the crop. Tomatoes are attacked by a variety of pests the most common being;

Red spider mites

These appear as oval, reddish greenish with eight legs that infest tomato leaves. They spin silk threads that help anchor their eggs to the underside of the leaves. A red spider mite infestation  is characterized by; 

• Damages to the plant leaves, causing it to show white to yellow speckling, which later turns bronze. 
• Smaller and lighter fruits produced by the plant.

To control red spider mites, you should employ the use of pesticides such as Spiromesifen and Amitraz. Red spider mites quickly develop resistance to pesticides when used continuously. You should, therefore, use miticides with different modes of action and active ingredients and only use the recommended dosage.

African Bollworm

This is a type of moth that is yellow to brown that lays its eggs near or on the flowers or small fruits. 

The eggs hatch into larvae, which then causes damage to the fruit. An African Bollworm damage characterized by;

• Flower abortion by the plant and sunken necrotic spots.
• Attacks by bacteria and fungi from the holes left by the larvae, which lead to rotting of the fruit.

To control the African Bollworm, you should till and plough old tomato fields to expose pupa to desiccation and natural enemies. 

You can also plant trap crops such as Maize and African Marigold, which attract the pest before it attacks the tomatoes. You can also make use of selective pesticides, such as microbial control agents.

Thrips

These are slender winged insects whose both adult and nymph feed on the bottom side of the leaf, buds, flowers, and also the fruits. 

Thrips are also responsible for transmitting the Tomato Spotted Wilt virus disease. Damage from thrips is characterized by;

• Speckling and small necrotic patches on the leaves
• Premature dying and slowing in leaf development. Also, thrips cause distortion of young shoots.
• Flower abortion in cases where the thrips have attacked the buds.

To control thrips, you can employ the use of insecticides such as Lambda-Cyhalothrin. You can also plough and harrow the farm before transplanting to kill the pupa hiding in the soil.

Weed Control In Tomatoes

Weed control is vital in reducing competition for nutrients between weeds and tomato plants. 

Slash or uproot the weeds to control weeds on open land crops between rows of tomatoes. Ensure that you remove the cut weeds as they may be carriers of diseases such as bacterial wilt that may affect your crop

Slashing should be supplemented with manual weeding. You can also uproot the weeds by pulling them by hand. 

You should avoid weeding Tomato fields when the soil is wet as it can increase the spread of some diseases such as Bacterial wilt and Fusarium wilt.

Pruning Tomatoes

Pruning is a fundamental process, especially for an indeterminate variety of tomatoes. 

It involves the removal of extra flowers, side shoots, fruits, and diseased leaves weekly. Pruning leads to the early maturity of fruits and encourages fruits to increase in size and uniformity.

Also, Leaves closer to the soil should be removed to discourage entry of early or late blight.

Intercropping Tomatoes

Intercropping is essential in ensuring you maximize your returns from your farm. Choosing the right crop to intercrop with your tomatoes is crucial as it will affect the health of your tomatoes. 

In addition to maximizing your returns on your farm, some plants may be beneficial in controlling pest and disease attacks. 

Some plants you can intercrop with tomatoes include; amaranth, basil, beans, carrots, cucumber, garlic, lettuce, onion, parsley, peas, sage, and stinging nettle. Benefits of intercropping tomatoes with such crops include;

• Basil helps repel insects such as fruit flies and diseases. It also improves the growth of your tomatoes and its flavor. 
• Growing borage with tomatoes aids in improving the growth and taste of tomatoes. It also helps in repelling tomato worms.
• Bee balm, chives,  mint, and parsley better the health and flavor of your tomatoes. 
• Garlic helps repel red spider mites. You can also use garlic sprays to aid control late blight.

DO NOT intercrop tomatoes with plants such as eggplants and potatoes as they are in the same nightshade family, thus making it easier for diseases such as early and late blight to spread.

Tomato Harvesting and Post Harvest Handling

Depending on the variety and environmental conditions, your tomatoes will mature in between 3-4 months. 

Before you start thinking about your money, it will be very prudent of you to harvest your tomatoes in stages. 

Harvesting Tomatoes

The stage you will harvest your tomatoes in is dependent on your client’s desire and the distance from your farm to the market. The main four stages you can harvest your tomatoes in are;

1. Mature-green stage – this is when your fruit is mature but still green in colour. Harvesting while at this stage will give you adequate time to transport your tomatoes to the market. You should be careful not to harvest the tomatoes prematurely if you intend to harvest them while in this stage.
2. Breaker or turning stage – This is when up to 30% of the fruit surface has changed from green to yellow.
3. Pink to light red stage – This is when 30-90% of the fruit has a pink or red colour
4. Red stage – This is when the fruit is completely ripe and ready to be consumed. Harvesting during this stage means the fruit has a shorter storage time and should only do it when the market is ready to receive your produce.

You should try as much as possible to harvest your fruits early morning when the temperatures are still cold. 

The harvested fruits should be placed in a cool shaded, and ventilated area to prevent heat and ethylene buildup, which speeds up the ripening process.

Post-harvest Handling of Tomatoes

You should clean your harvested tomatoes using a clean damp cloth to remove any excess chemical residue and dirt that might be on the fruit. You should also separate damaged and diseased tomatoes to prevent the spread of infection to healthy tomato fruits.

In preparation to sell your products to the market, it is important to sort your tomatoes according to size and colour. This will divide your harvested produce into grades to reap maximum benefits.

Marketing Your Tomatoes

Tomatoes have a very huge market in Kenya. Given that almost all Kenyan homes use tomatoes as part of the ingredients of their daily meals, you are sure never to miss a market for your produce. 

To avoid the tomato glut that lowers the price of your farm produce, you should ensure that you schedule your growing and harvesting season to fall during the time that the demand is at the highest. In Kenya, tomato demand is usually highest between December and April during the onset of the long rains.

Farmers in Kenya produce an average of 283000 tonnes of tomatoes against a demand of 300000 tonnes. The shortfall has to be delivered from neighboring countries. The current market price for tomatoes stands at Ksh.130 per kilo. 

Some of the bulk buyers of tomatoes are companies that make tomato products such as juices, purees, tomato paste, and sauces.

Aside from tomato processing factories, other huge buyers of tomatoes include;

• Hospitals
• Primary and secondary boarding schools.
• Hotels and restaurants.

Processing your tomatoes can help shield you from losses in case you harvest your tomatoes when there is a glut in the market. Slicing and sun drying is a simple method you can use to lengthen the shelf life of your tomatoes.