Optical sorters for tomato harvesting
Protect’s history is rooted in the self-propelled tomato harvesters designed by Luigi Sandei, its Founder. Thanks to our history and the continuing investment in skills and technology, we can apply a wide knowledge in cultivation techniques to our industrial project. This allows us to develop leading edge technology sorters that can be installed on any model of self-propelled tomato harvester.
Quality is our goal: use our experience for your product
The staff of Protec Sorting Equipment has in-depth knowledge of the tomato growing processes. We support our customers along each production step in their agri-food projects. Our sorters are engaged in the final phase of the harvest, but we support each cultivation step to ensure the high quality of the finished product, a tomato crop fit for the processing industry.
Cultivation technique – Sequence in crop rotation
Tomato is a typical rotation crop in open-field cultivation. It is therefore not advisable to repeat cultivation on the same field within too short intervals. To prevent the pathogens loads of parasitic fungi and nematodes from increasing, a pause of at least 3-4 years must be observed. During this period, the soil cannot host other Solanaceae (tobacco, bell pepper, aubergine, potato) that suffer from the same problems in terms of parasites. In greenhouse cultivation is more difficult to respect crop rotation rules, and often disinfection with fumigants as well as soil sterilant are employed to eliminate pathogens present in the soil.
Soil preparation for tomato cultivation must be accurate, especially where planting is carried out with in-field sowing.
The sequence of operations generally includes deep tillage (40-50 cm) in the previous summer and supplementary works during fall and winter, such as shaping the rows and improving soil particle size. To obtain the perfect soil conditions required by the seeds’ small size, in clay terrain is better to carry out advanced preparation of the seedbed by vigorous harrowing that breaks the ground structural layer.
In some cases, tomato crops are not planted on levelled surface, but on shaped terrain, in narrow stripes separated by ruts that are used for lateral infiltration irrigation. In these cases, the soil needs to be suitably prepared before sowing or transplanting.
Tomato must have adequate supply of needed nutrients such as mineral fertilizers even in cases, increasingly less frequent, where manure or some other organic fertilizers are available.
The amount of fertilizer needs to be measured to the soil productivity and the macronutrients already present in the soil itself.
In very intensive greenhouse cultivations with high-yield (120-150 t/ha and more), fertilizers are recommended in the following quantities: 100-150 Kg/ha of P2O5, 200-250 Kg/ha of K2O, 250-300 Kg/ha of nitrogen. In case of open-field cultivations, the yield is lower than in greenhouses, however, we need to make a distinction between dry and irrigated farming.
In irrigated farming, desirable yields range between 80-100 t/ha and the quantity of fertilisers ought to be: 100-120 Kg/ha of P2O5, 150-200 Kg/ha of K2O and 180-200 Kg/ha of nitrogen; in dry farming with yields around 20-30 t/ha the quantities of fertilisers ought to be reduced. Phosphorus and potassium fertilisers are placed below surface during soil preparation, while nitrogen fertilisers need to be placed partly during sowing or transplanting (1/2-1/3 of the total, such as urea) and partly topdressing (such as urea or ammonium nitrate).
Tomato crop can be planted by in-field sowing or transplanting.
Transplanting requires growing seedlings in a seedbed, generally enclosed, to ensure temperature suitable for germination. It can be done by broadcast sowing on the seedbed, or placing single seed in containers (cell flats, biodegradable pots) or blocks of potting soil; in the first case the plants are transplanted with bare root, in the other cases together with the ball of soil.
Sowing in a seedbed guarantees various advantages: time-saving, faster growth, greater evenness, less seeds used.
Seedbed sowing is done at various periods according to the type of crop desired: autumn-begin of winter for greenhouse cultivations; winter for early maturing crops, temporarily protected; end of winter (February-March) for open air crops in full season; summer for cultivations on a late maturing cycle.
1 square metre of seedbed can produce 500-600 seedlings suitable for transplant, which are obtained from sowing 2-3 grams of seeds corresponding to 600-900 seeds per square metre. Each hectare of crop requires 60-80 square metres of seedbed, with placement density of 3500-4500 seedlings per hectare.
40-60 days after seed sowing the tomato seedlings reach the stage of having 4-5 leaves and the height of 100-150 mm: this is the best time for transplanting.
Transplant of processing tomato in open-field cultivations takes place from mid-April to mid-May. In open-field, double row planting is widely used and we will discuss it later in reference to direct seeding.
The transplant is done either by hand or with a machine; seedlings grown in cell flats with their ball of soil adapt well to the latter method.
Direct Seeding is expanding in open-field cultivation because of its benefit in reducing planting costs and yielding strong plants, especially in the root system, as they do not need to overcome the stress of transplant. Negative aspects are: higher quantities of seeds are used, the seedbed requires accurate preparation, a certain amount of thinning may be required, sowing cannot be done before the air temperature reaches the minimum level needed (about 12 °C) to ensure germination and reasonably quick sprouting.
Tomato can be sowed with extra seeds (1-1.5 Kg/ha) postponing the elimination of the plants in excess until the thinning out process; or 0.4-0.5 Kg/ha of seeds can be sowed using a precision seed driller, in which case thinning out can be omitted.
Placement of the plants, therefore the seeds, in the soil can be done in simple rows spaced at 1-1.5 m distance, but it is mostly done in double rows having 0.30-0.40 m between each rows and 1.3-1.5 m between the double row.
The double row presents various advantages:
- The leaves provide better shading for the berries;
- Less side-shoots and better simultaneous ripeness due to the strong competition among the plants in the double row;
- Lower cost for drip irrigation (quite common) due to the reduced length of driplines;
- Easier mechanical harvesting.
The investment varies from 3 plants every 2 m for simple row crops to 6-8 in case of double row.
Seeding depth cannot exceed 20-30mm given the small size of the seeds.
Use of the precision seed driller with pelleted seeds favours uniform sowing, as the seeds’ rough surface otherwise would tend to make them stick together.
Open-field tomato seeding is done in the spring: towards March in more mild Southern regions, and in April in the Central-Northern regions.
Transplanting always needs additional irrigation to ensure rooting. After seeding, soil rolling can enhance seeds moisture and germination.
Hoeing is recommended not only to control weeds, but also to air the soil and reduce evaporation.
In many cases, mulching with black plastic film is practised: in general associated with double row planting and drip irrigation. The dripline is placed at the centre of the double row, below the mulch sheeting. High costs are offset by great advantages in terms of agronomics and quality (clean products).
Installation of supports is needed for the greenhouse varieties or other open-air varieties (San Marzano) having undetermined growth. For these varieties certain special operations are performed, such as: pruning to eliminate axillary shoots and keep a single stem plant; topping, i.e. trimming the plant by leaving 3-6 trusses to enhance maturation of the fruit on the trusses left in place; treatments with growth regulators that in greenhouse cultivations favour fruit set and development of parthenocarpic fruit.
Irrigating increases and stabilises yields even though it does not always enhance the quality of the fruits. For salad tomatoes frequent and light irrigation is preferable; whereas less frequent and more abundant irrigations are more advisable for processing tomatoes, making sure to water well in advance of the harvest. In case of limited availability of water resources, some water savings can be achieved during the vegetative phase and during ripening, but water should not be lacking during the flowering phase. Poor water management can create damages in sensitive varieties such as blossom end rot, fruit cracking and scorching.
The sprinkler irrigation method is not free from drawbacks (it promotes fungal diseases and bacterial canker); the lateral infiltration method is one of the most frequently used, and drip irrigation is more and more used: both methods have the advantage of not wetting the plants.
If seeding is done on a substrate poor in nutrients, such as vermiculite, fertigation products must be used at a very early stage just after germination, with a nutrient solution containing from 1 to 2 gr/litre of fertilizer rich in phosphate (Monoammonium phosphate or a complete NPK).
Basal dressing includes phosphorus and potassium. It is recommended to distribute nitrogen partly before transplanting, using prolonged action types of nitrogen (ammoniacal or slow release), especially in light soil, and the remaining part as topdressing.
It is better to transplant in soil already fertilized, should that not be possible, a nutrient solution of 1.5-2 gr/litre of fertilizer can be used and the following procedure should be adopted: moist the substrate with a nutrient solution before the transplant, followed by watering with the solution prepared. A complete NPK fertilizer can be used to prepare the solution, using a ratio close to 1-1-2.
If the transplant is done in well-nourished soil, fertigation starts at the third leaf level.
Topdressing fertilizing will distribute the remaining portion of nitrogen, according to the development of the crop, the seasonal weather and the technique of application, using quick-acting fertilizers, such as calcium nitrate, ammonium nitrate and potassium nitrate.
The distribution method is dependent on the plant’s rate of absorption of the nutrient.
Tomato has high water requirements, in particular during the phase of fruit setting.
In water-stress condition, the fruits become more subject to blossom-end rot (B.E.R.).
It is difficult to quantify precisely tomato’s water requirements, as fruit production varies.
Water needs can change according to areas of cultivation, time of planting, and the crop’s early growth. Generally, frequent actions are necessary, at least on a weekly basis, with water volumes ranging around 300-450 m3/ha/weekly.
The first watering should take place when the residual moisture content in the top 50 cm of soil is about 60%, measured with the tensiometer, or with water balance estimation.
Planning the irrigation and fertigation system is certainly among some of the most neglected aspects of irrigation management. Use of non-suitable materials can almost nullify the effectiveness of fertigation activities or cause considerable damages to the crop and the environment.
Traditional drip tape, for example, is not suitable for effective fertigation, due to a well-known uneven distribution of water. Nowadays new self-adjusting driplines are available. They allow even distribution of water from the drippers, also in very long drip irrigation systems or on sloping terrains.
On average, tomato plant can be considered tolerant to salinity; therefore, water with moderate salt content, 1-1.5 per thousands, can be used.