Increase tomato production by pruning and trellising

Increase tomato production

by pruning and trellising

Pruning and trellising tomato plants can be done by plants with indeterminate growth habit. This will shape them for better production and enhance air circulation and ventilation, optimize space and sunlight, improve growth balance between roots, leaves and fruit, and enhance the working space.

ADVANTAGES OF TRELLISING

1. Reduces the incidence of physiological disorders e.g. fruit cracking and the uneven ripening of fruit due to exposure to high solar radiation and high temperature 2. Reduces the incidence of fruit rot and soil-borne diseases 3. Maximizes the efficiency of photosynthesis 4. The upright plants have fewer disease problems with leaf spots and fruit rots because their leaves stay drier and are not in contact with pathogen laden soil

POSSIBLE DISADVANTAGES

1. Requires expertise (good management and skilled workers) 2. Trellising and pruning need to be done regularly – labour intensive 3. Plants can be damaged during training and harvesting

Pruning

Pruning is simply the removal of the side shoots or suckers which develop between the main stem and the leaf. It helps to maintain a balance between vegetative and reproductive growth. Generally, if you do not prune or prune few side shoots, your plant will show excessive vegetative growth which may result in smaller fruit size. Care should be taken not to prune the growing point of the main stem otherwise your plant will stop growing and bearing fruit.

Removal of sucker/side-shoot with the thumb and forefinger

Suckers can be removed with thumb and forefinger by pulling outwards. They are removed while they are young and succulent (2 to 5 cm long) when they heal faster. Large suckers are not easily removed and can create a larger wound, which takes time to heal and can be an entry point for pathogens. Experimental evidence has shown that there is a high reduction in yield when side shoots are allowed to develop 15-20 cm in length because they use nutrients which should go into fruit development. When working with big-suckers, it is important to remove the growing point of the sucker, causing less shock to the plant. Removing big suckers may necessitate using a knife, shears or scissors. It is important to disinfect the instrument after cutting to prevent diseases being spread from one plant to another. Pruning of suckers is known to increase the size of the fruit and promotes early harvesting. Determinate cultivars are not supposed to be pruned, but the leaves below the

Sucker/side-shoot Growing-point

Side-shoots

iNcREAsE TomATo PRoDUcTioN BY PRUNiNG AND TREllisiNG 4

first truss can be removed to enhance air circulation. Pruning does not affect the fruit size or the vegetative growth of determinate cultivars if pruning is done below the first truss. Pruning of suckers above the first truss will result in lower yield. When the plant matures, especially when the first two trusses have been harvested, lower leaves turn yellow. Generally, remove yellow leaves below the ripening fruit clusters. These yellow leaves should be snapped off with fingers and removed as they are not actively photosynthesizing. In addition, this will enhance air circulation around the base of the plant, and will help to reduce fungal and bacterial disease build-up. This can be done by holding the main stem with one hand and snapping off the leaf where it is attached to the main stem using the other hand. It is important not to remove the green leaves since they function as a source of food supply to the fruits. The figure below shows how a plant should look after removing the old leaves. Old leaves should be removed far from the production area and destroyed to prevent the spreading or build-up of diseases. Removal of the older leaves results in trusses facing towards the walkway, which makes easy to 7

Removal of the older leaves results in trusses facing towards the walkway, which makes easy to harvest.

Trellising shows the stem twisted around the twine, which is attached to the stay wire.

TomATo PRoDUcTioN iN A GREENhoUsE is A DEVoTED TRADE 4

These increases in climatic energy levels equate to increased water use by plants, mainly for evaporative cooling. In the case of indeterminate growers like tomatoes (that were transplanted for the summer production), a further complicating factor is the exponential plant development associated with the first rapid plant growth until roughly the onset of the harvest period. During winter, fertigation EC’s are maintained at a relatively high level in an attempt to “force” as much nutrition into the plants during these periods of lower water usage. Inversely, the EC should be gradually reduced as the warmer season progresses due to the higher water usage. If the Ec is not reduced in time, plants may reach a “salt saturation point” and “shut down” transpiration temporarily. This is to protect the cells from damage due to excessive salt build-up in the plant. Typical wilting during the midday period can be ascribed to this “shutdown”. Blossom end rot often results from this periodic wilting. At the same time as reducing EC, the water volume will have to be increased to match the transpiration of the plants. The plants’ water volume requirement will have to be upgraded daily due to the warmer weather as well as the expected rapid growth of young pre-harvest plants. This increasing need for water is echoed by the growing need for minerals as the plants need more and more nutrients to fuel the rapid growth. The relative nutrient balances must be maintained over the growth period, with careful attention for the need in Potassium during and after flowering – especially in fruiting vegetables like tomatoes. With high radiation conditions, excessive root EC or salt build-up is one of the main factors resulting in production losses. For example, Tomato plants with thick stems, compacted internodes, deformed growth points and poor or no fruit set are examples of a too high salt load on the plant. As a broad generalization, growers tend to over-fertilize in an attempt to boost growth. Sometimes high root zone salinity can also be ascribed to a watering regime not suited to climate, or simply, inadequate water volume to facilitate sufficient flushing of the root zone (run-off % too low). EC levels should be low to maintain good growth and allow plants to continue transpiration throughout the day. Fertilizer mixtures containing significant levels of Chlorides (often in an attempt to lower the cost of fertigation) increase the relative EC of the mixture. Programs with no or very low Chloride levels, especially for summer, will help in reducing the ion load on the root system – allowing easier uptake of beneficial minerals and further aiding the prevention of salt build-up in the roots. Successful warm weather fertigation can be “summarized” as: a program which allows the plant to optimally utilize water for evaporative cooling, transport of sufficient and balanced nutrients plus enough oxygen for healthy root function & growth. Source: P de Vries (abridged version)

iNcREAsE TomATo PRoDUcTioN BY PRUNiNG AND TREllisiNG 6

harvest. Indeterminate cultivars grow very tall, and with time the yield and fruit size become progressively smaller. Removing the growing points of a plant will stop growth and enhance fruit ripening. With approaching low temperatures (frost), it is important to prune the growing points of all the plants. This is because tomato is sensitive to low temperatures, so by removing the growing points will stop fruit bearing and ripening of fruits will be enhanced.

Trellising

Trellising is done by tying twine from the bag to the stay wire above the plant. The stem is then twisted around the twine to give support. Trellising should be done two weeks after transplanting. If transplants are not trellised at early stage, they become crooked and trellising then will result in breaking or damaging the plant. Normally a tomato plant may grow approximately 5 – 6 m in a 6 month growing season. It is therefore important that the stay wires are strong enough to carry the mass of a whole row of plants with fruit. The total mass of the plants and fruit in a 45 m row is more than 1 ton. Therefore, considerable damage to plants will result if the stay wire breaks at the height of the production season. By: Martin Maboko

The growing habit of the scion changes during the different seasons – it grows more generative during summer and more vegetative during the winter. Planting the right rootstock in the right season will help your plant overcome the difficulties. The De Ruiter brands; Maxifort is a good option for summer, while a more generative rootstock like Beaufort is more suitable for winter. However, there are companies like Histhil and Eza Zaden that are also producing excellent rootstock for various greenhouse plants. Disease pressure can be another reason to graft. The main problem in SA is with Fusarium and Verticillium. The common rootstocks will provide resistance to these diseases and in combination with the stronger vigour the plant will be less susceptible to secondary diseases like bacterial wilt and bacterial canker. The regulations regarding the use of agrochemicals play a role in the selection of the correct variety and rootstock. Rootstocks with resistance to bacterial wilt are on the market as well. Several seed companies have concluded successful trials in the RSA. GRAFTinG AnD FRuiT quAliTy Fruit is the genetic result of the scion and not a direct result of the grafting. indirect effects such as water and nutrient availability or carbohydrate metabolism, can alter the quality and all these factors may be highly variable based on the rootstock genotype. CoST oF GRAFTinG Additional labour, grafting clips and rootstock seed add to the cost of a seedling. on commercial specialty types of tomato only 250gm more fruit per plant pays for the grafting. in various super-chain trials, growers are already picking more fruit per plant on their grafted seedlings. For the standard round-type of tomato grafting offers the benefit of a longer picking time and therefore more trusses per plant. With growers increasing their yields from 180 to 220 tons per hectare, grafting is not costly, but a financial survival tool. important to understand though, is that whatever scion you will grow on any rootstock, the key to success depends on plant balance! (R Gillies)

A tomato scion grafted on rootstock to increase production and free the plant from root diseases. Pic: JS