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Tomato is one of the most widely grown vegetables in the world. The popularity of tomato among consumers has made it an important source of vitamins A and C in diets.Climate and soil requirements.Tomatoes grow best in temperatures 20–27°C. Fruit setting is poor when average temperatures exceed 30°C or fall below 10°C. Tomatoes prefer welldrained soil because they are sensitive to waterlogging. Optimum soil pH is 6.0–7.0. Tomatoes benefit from crop rotation. Growing tomato after paddy rice, for example, reduces the incidence of disease and nematodes. Avoid planting tomato in a field planted the previous season with tomato, pepper, eggplant, or other solanaceous crop. These crops share some insect and disease problems.
Choosing a variety
Selecting the best variety is critical for success. There are many factors to consider: Fruit type. Tomato varieties are grouped into one of three market classes:
(1) fresh market—fruit are usually red but vary in color, shape, and size;
(2) cherry—a small-fruited (less than 30 g) fresh market type borne on long clusters; and
(3) processing—fruit have intense red color and high solids content suitable for making paste, catsup, or sauce. Plant habit. Tomato varieties are also classified according to plant habit: determinate, semi-determinate, or indeterminate. Determinate and semideterminate varieties produce stems that end with a flower cluster. Determinates are short and bushy while semi-determinate varieties grow slightly taller. Indeterminate varieties continually produce new leaves and flowers, and can grow very tall. Indeterminate varieties set fruit over a longer period. This longer harvest period is an advantage if market prices fluctuate, because income tends to even out. Indeterminate varieties should be staked and pruned and usually require more labor.
Disease resistance. Prevalent diseases vary according to location and environment, but bacterial wilt, bacterial spot, tomato yellow leaf curl virus, fusarium wilt, and gray leaf spot are common in the tropics and subtropics. Some varieties are resistant to many diseases. Information on a variety's disease resistance can often be found on the seed packet. Adaptation to season. Most tomato varieties are adapted to the dry season. Tomato varieties able to set fruit at temperatures greater than 30°C can be grown during the hot season to take advantage of higher market prices. AVRDC has developed tomato lines suited to the hot, wet season. However, successful wet season production requires a combination of a suitable variety and special management practices, such as use of fruit-set growth regulator, raised beds, grafting, or shelters to manage
Hybrid or inbred? Hybrid varieties are gaining popularity because they often produce higher yields and more uniform fruit compared to inbred lines. However, a hybrid is not always superior to an inbred variety. Hybrid seed is usually more expensive than inbred varieties, and seed cannot be harvested for future planting. Seeds of inbreds can be harvested and saved for future planting.
About 250 g of seed (approximately 70,000 seeds) are required to produce enough seedlings to plant one hectare of an indeterminate variety and 125 g of seed for a determinate variety. Sow seeds 0.5 cm deep.
Seedlings will emerge within 8 days at the optimal soil temperatures of 20–30°C. Seedlings grown in trays of individual containers are healthier and more vigorous compared to those grown in flats or beds. Seedlings grown in flats or beds suffer root damage when the plants are pulled apart for transplanting. At AVRDC we grow 33,333 plants/ha for indeterminate varieties (which are pruned), and 16,666 plants/ha for determinates (which are usually not pruned). Plan to sow twice as many seeds as are needed in order to make sure there are enough plants.
Seedling tray method. Fill the holes with a medium that drains well, such as peat moss, commercial potting soil, or a mixture of sand, compost, and burnt rice hulls. Place the trays on benches in a sheltered place. Sow 2 seeds per hole and thin the seedlings 2–3 days after the first true (noncotyledon) leaves appear. Seedbed method. Choose a well-drained area not recently cropped with a solanaceous crop. Burning a 3–4 cm layer of rice straw on the seedbed before sowing, and forming a raised seedbed of 15 cm or higher to improve drainage, can reduce soilborne disease problems. Sow the seeds in rows 6 cm apart at a rate of 750–900 seeds/m2. Cover the bed surface with a thin layer of compost or rice straw mulch. Do not allow the soil to dry and form a crust on the surface that might hinder seedling emergence. Water the seedbed regularly so that it is moist but not waterlogged. Thin the seedlings 2–3 days after the first true (non-cotyledon) leaves appear.
At the two-leaf stage, irrigate the seedlings once with a 0.5% ammonium sulfate solution (5 g ammonium sulfate dissolved in 1 liter of water), 0.25% urea solution (2.5 g urea dissolved in 1 liter of water), or 0.1% Nitrophoska solution (1 g dissolved in 1 liter of water). Do not over-apply nitrogen or the plants will grow tall and thin. Seedling death (damping-off) or poor growth can be due to fungal infection. Fungicides, such as Ridomil Gold (mefenoxam), can be applied to the seedbed at or before seeding to control pythium damping-off. Seed can be treated with broadspectrum fungicides, such as captan and/or thiram to reduce losses from damping-off.
Insects, such as whiteflies, thrips, and aphids, can transmit viruses to young tomato plants. Admire (imidacloprid) is effective as a seed, soil, or foliar treatment for these insects. If whiteflies are a problem in the nursery, we recommend that tomato seedlings be covered with a net, 60-mesh or finer, to prevent insect infestation.
Harden the seedlings by slightly reducing water and exposing them directly to sunlight 6–9 days before ransplanting. Thoroughly water the seedlings about 12 hours before transplanting to the field. A
good seedling is in the four- or five-leaf stage (about 4 weeks old), vigorous and stocky (Figure 2). Transplant in the late afternoon or on a cloudy day to minimize transplant shock. Insert the seedling in a hole so the cotyledons are above the surface. Tall, thin (spindly) seedlings should be buried deeper. Press soil firmly around the root, and water around the base of the plant to settle the soil. Irrigate the field as soon as possible after transplanting. Plant spacing depends upon cropping system, soil type, and plant habit. At AVRDC we establish two rows per 1-m-wide bed (60 cm between rows) and 40 cm between plants within the row for indeterminate varieties (pruned) for a plant density of 33,333 plants/ha. For determinate varieties (not pruned) we establish one row per bed with 40 cm between plants (16,666 plants/ha).
Figure 2. Spindly and healthy seedlings.
Shaping the land into beds and growing tomatoes on top of the bed facilitates furrow irrigation of the crop and drainage after heavy rain. Beds can be prepared in many ways. At AVRDC, beds are made with a mechanical bed shaper and are about 1 m wide with furrows (ditches) 50 cm wide. Bed height varies with the season: 20 cm in the dry season and 35 cm in the wet season. A mulch of rice straw, thin polyethylene plastic sheets, or other material is used to cover the soil surface. Mulches reduce fertilizer leaching, conserve moisture, and reduce weeds. If average air temperatures exceed 28°C, plastic mulch should be covered with rice straw to prevent it from getting too hot.
Tomato plants should be fertilized with organic (animal manure) and/or chemical fertilizers to produce high yields. The total N (kg/ha) required to achieve a target fruit yield is estimated by multiplying the target yield (t/ha) by 2.4. Requirements (kg/ha) of P205 and K2O are estimated by multiplying N uptake by 0.35 and 1.45, respectively. For example, for a potential tomato yield of 40 t/ha, you need 40 × 2.4 = 96 kg of N. For P2O5 and K2O, multiply the N requirement of 96 × 0.35 = 34 kg P2O5, and 96 × 1.45 = 140 kg K2O. The amount of NPK already in the soil can be estimated by a laboratory soil test. Addition of fertilizer is needed to make up the difference between the NPK requirement for the target yield and the NPK available in the soil. However, fertilizer uptake efficiency by a crop is highly variable and depends upon many factors, including fertilizer form and placement (surface versus incorporated versus banded), as well as irrigation and other management practices. In the tropics, common fertilizer application rates are 60–120 kg N/ha, 60–140 kg P2O5/ha, and 60– 120 kg K2O/ha. It is recommended that half of the fertilizer be applied as a basal dose and the remaining fertilizer be added at first fruit-set.
Source: This Research was Published on Horticulture International (http://hortintl.cals.ncsu.edu