All the cultivars which are commercially grown in the country have been introduced from other countries mainly from Europe and America. The principal cultivars grown are; Money Maker, Roma, Riogrande.
Province-wise nursery sowing, transplanting and harvesting times of tomatoes are given below
Tomato is very sensitive to cold. In most cultivars, flowering does not develop normally below 15oC or above 35oC. The optimum range lies between 21oC and 24oC. Seed germination does not occur in soil temperature below 10oC or beyond 35oC. The optimum range for germination occurs between mean soils temperatures of 15.5oC and 29oC. In the plains, most difficult period of tomato production is from mid May to June when the day and night temperatures are very high and during monsoon season (July-August) when there is a rapid development of pests, diseases and weeds.
Tomato thrives best almost on all types of soils. A well fertile sandy loam soil is best suited to produce early crop. The loams and clay loams have greater water-holding capacity and are better suited to longer season of production. Soils rich in organic matter and mineral nutrients are suitable for higher yields. Soils ranging from pH 5.5 to 7.0 are best suited for tomato production.
Preparation of land is necessary for growing successful crops. Well rotten farm yard manure should be applied @ 10-12 tons per acre at least one month before planting the crop for maintaining proper physical conditions and fertility status of the soil. Five to six ploughings will be needed to prepare a good seed bed. The ploughed land must be disked well and should be thoroughly leveled for even distribution of water. Raised beds of 1.5 m breadth should be made.
As much as 120 to 150 g of seed is required to prepare nursery for one acre.
Transplants for open field can be raised in the plastic tunnel if they are to be grown in a season when climatic conditions outside would not be favourable for growth. Mixture of well rotten farm yard manure, sand and soil in the proportion of one part each is commonly used as medium for growing transplants.
Seedlings of 15-25 cm tall with 3-5 true leaves are most suitable for transplanting. Before transplanting, the seedlings should be hardened by gradually reducing the frequency of irrigation and exposing the seedlings to strong sunlight. The seedlings in the nursery beds should be watered on the day before transplanting. Transplanting of seedlings in the field should be done late in the afternoon to curtail transpiration of the seedlings. The soil around the roots of the shifted plants should be well pressed to ensure a good contact with the roots and the plants are irrigated immediately. The seedlings are transplanted on both sides of 1.5 meter wide raised beds with plant to plant distance of 50 cm.
General recommendation for chemical fertilizer to be applied is, 46 kg Nitrogen, 60 kg Phosphorus and 25 kg Potash per acre. For better results, full quantity of Phosphorus and half of Nitrogen and Potash should be applied before transplanting of seedlings. Remaining half of Nitrogen and Potash should be applied 6-8 weeks after transplanting.
Tomato is not resistant to drought. Yields decrease considerably after short periods of water deficiency. It is important to water the plants regularly, especially during flowering and fruit formation. The amount of water that is needed depends on the type of soil and on the weather (amount of rain, humidity and temperature). About 20 mm of water per week is needed under cool conditions, about 70 mm during hot and dry periods. Watering plays a major role in attaining uniform maturity and reducing the incidence of blossom end rot, a physiological disorder associated with irregular water supply and the resulting calcium deficiency in the fruit during its enlargement. The plants are irrigated just after transplanting. Irrigation with an interval of 7-8 days is recommended. The irrigation interval can be decreased from 5-6 days when weather is too hot. Irrigation water should be given in sufficient quantity but with care so that beds should not be submerged into water.