Complete guide to open field tomato farming

Varieties and their yields

There are categories of tomato varieties, namely determinate and indeterminate. 
Determinate tomato varieties grow to a standard height of about one metre. 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 two metres. Indeterminate will flower, set new fruit and ripen fruit all at the same time throughout the season. They require substantial staking for support.

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;
It can yield up to 18tonnes per acre.

The Rio Grande matures in between 75–85 days. 
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;
Assila F1 is an early maturing variety taking 75days to mature after transplanting.
It is tolerant to Tomato Yellow Leaf Curl Virus and nematodes.

This variety can yield up to 23tonnes per acre.
It can be stored well and transported without much damage.

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. 

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

Fertiliser 
Fertiliser plays a vital role in the development of excellent and healthy tomato plants. Before fertiliser 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 grammes of DSP to each hole. Ten grammes 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 80 kilogramme per acre. 
If available, you can also apply manure at the rate of eight tonnes per (about two handfuls per each hole).

Irrigation 
Tomatoes are susceptible to water stress in the following two stages;
Immediately after transplanting. 
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.

Weed control 
Weed control is vital in reducing competition for nutrients between weeds and tomato plants. 
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. You can also uproot the weeds by pulling them by hand. 

Pruning 
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.

Diseases 
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; Fusarium wilt, Blossom-end rot, Tomato Mosaic virus and bacterial wilt among others.

You can control these diseases by using resistant varieties. 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. You can as well spray your crop with calcium chloride to boost calcium levels in your farm.

You can also do spot treatment of infected plants by spraying infected plants with sodium hypochlorite 10 percent (simply JIK) or use lime or ash.

Pests 
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 characterised 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 characterised 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. 

Harvesting
Depending on the variety and environmental conditions, your tomatoes will mature in between three and four months. 
Before you start thinking about your money, it will be very prudent of you to harvest your tomatoes in stages. 
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;

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.

Breaker or turning stage - This is when up to 30 percent of the fruit surface has changed from green to yellow.
Pink to light red stage - This is when 30-90 percent of the fruit has a pink or red colour.

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 build-up, which speeds up the ripening process.

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.

Weed control 
Weed control is vital in reducing competition for nutrients between weeds and tomato plants. Uproot the weeds to control weeds on open land crops between rows of tomatoes.

Harvesting 
Depending on the variety and environmental conditions, your tomatoes will mature in between three and four months.  Before you start thinking about your money, it will be very prudent of you to harvest your tomatoes in stages.

- Adopted from: value.co.ke