TOMATO AGRONOMY PRACTICE

Introduction

Tomato is a warm season crop, it requires warm and cool climate. The plants cannot withstand frost and high humidity. Also light intensity affects pigmentation, fruit colour, fruit set. The plant is highly affected by adverse climatic conditions. It requires different climatic range for seed germination, seedling growth, flower and fruit set, and fruit quality. Temperature below 10 C and above 38 C adversely affects plant tissues thereby slow down physiological activities. It thrives well in temperature 10 ℃ to plant tissues thereby slow down physiological activities. It thrives well in temperature 10 ℃ to 30 ℃ with optimum range of temperature is 21-24 ℃. The mean temperature below 16 ℃ and above 27 ℃ are not desirable. The plant doesn’t withstand frost, it requires low to medium rainfall, and does well under average monthly temperature of 21 to 23 ℃. Avoid water stress and long dry period as it causes cracking of fruits. Bright sunshine at the time of fruit set helps to develop dark red coloured fruits.

Suitable Soil

Tomatoes do very well on most mineral soils, but they prefer deep, well drained sandy loams.Upper layer of soil should be porous with little sand and good clay in the subsoil. Soil depth 15 to 20cm proves to be good for healthy crop. Deep tillage can allow for adequate root penetration in heavy clay type soils, which allows for production in these soil types. Tomato is a moderately tolerant crop to a wide pH range. A pH of 5.5- 6.8 is preferred. Though tomato plants will do well in more acidic soils with adequate nutrient supply and availability. Tomato is moderately tolerant to acid an soil that is pH of 5.5. The soils with proper water holding capacity, aeration, free from salts are selected for tomato cultivation. Soils extremely high in organic matter are not recommended due to the high moisture content of this media and nutrient deficiencies. But, as always, the addition of organic matter to mineral soils will increase yield.

land preparations

The ideal seedbed should be 60cm wide, 5-6cm long and 20-25cm high. Clods and stubbles should be removed from the seedbed. Add sieved FYM and fine sand on the seedbed. Bring them to fine tilth. Drench the bed with Fytolon/Dithane M-45 @ 2-2.5 g/lit of water. Draw the lines 10 to 15cm apart throughout the length of the seedbed. Sow the seeds thinly spaced in lines, press gently, cover with fine sand and then cover the bed with straw. Irrigate with rose can. Irrigate the seedbed twice a day till the seeds germinate. Remove the straw after the seeds germinate. Apply a little Thimet at 4-5 leaf stage. Spray the seedlings with Metasystox/Thiodan @ 2-2.5 ml/lit water and Dithane M-45 @ 2-2.5 g/lit water.

Sowing Time

1. Tomato is a day neutral plant so wildly it found grown in any season.
2. In the northern plains three crops are taken but in frost affected area rabi crop is not fruitful. The kharif crop is transplanted in July, rabi crop in October – November and zaid crop in February months.
3. In the southern plains where there is no danger of frost, The first transplanting is done in December-January, Second June-July Third in September-October depending on the irrigation facilities available.

Method of Sowing

Tomato is generally cultivated by transplanting seedlings on ridges and furrows. At the time of transplanting seedlings are harder by exposing to open weather or by withholding irrigation. A seed rate of 400 to 500g/ha is required. Seeds are treated with Thiram @ 3g/kg of seed to protect from seed born diseases. Seed treatment with B. naphthoxyacetic acid (BNOA) at 25 and 50 ppm, gibberllic acid (GA3) at 5- 20 ppm and chlorophenoxy acetic at 10 and 20 ppm was found to improve the growth and yield of tomato. Seeds are sown in June July for autumn winter crop and for spring summer crop seeds are sown in November. In the hills seed is sown in March April. The spacing recommended for the autumn winter crop is 75 x 60cm and for spring summer crop 75 x 45cm.

Spacing for tomato cultivation

The spacing recommended for the autumn-winter crop is 75 x 60 cm and for the springsummer crop 75 x 45 cm.

Transplanting for tomato cultivation

1. The transplanting is done in small flat beds or in shallow furrow depending upon the availability of irrigation.
2. In heavy soil it is usually transplanted on ridges and during the rains also it is advantageous to plant the seedlings on ridges.
3. For indeterminate varieties/hybrids, the seedlings have to be staked using bamboosticks of two meter length or planted in broad ridge of 90 cm width and 15 cm height. The seedlings are planted in the furrows at a spacing of 30 cm and the plant is allowed to spread on the broad ridge.

Application of manures and fertilizers

Apply well rotten farm yard manure / compost @ 20-25 t/ha at the time of land preparation and mix well with the soil. A fertilizer dose of 75:40:25 kg N:P O :K O / ha may be given. Half the dose of nitrogen, full phosphorus and half of potash may be applied as basal before transplanting. One fourth of nitrogen and half of potash may be applied 20-30 days after planting. The remaining quantity may be applied two months after planting.

As the fruit production and quality depends upon nutrient availability and fertilizer application so balance fertilizer are applied as per requirement. The nitrogen in adequate quantity increases fruit quality, fruit size, color and taste. It also helps in increasing desirable acidic flavor. Adequate amount of potassium is also required for growth, yield and quality. Mono Ammonium Phosphate (MAP) may be used as a starter fertilizer to supply adequate phosphorus during germination and seedling stages. Calcium availability is also very important to control soil pH and nutrient availability. Sandy soils will require a higher rate of fertilizer, and more frequent applications of these fertilizers due to increased leaching of essential nutrients. The seedlings are sprayed with starter solution of micronutrient. Before planting farm yard manure @ 50 ton per hectares should be incorporated. Normally tomato crop requires 120kg Nitrogen (N), 50kg Phosphorus (P O ), and 50kg Potash (K O). Nitrogen should be given in split doses. Half nitrogen and full P O is given at the time of transplanting and remaining nitrogen is given after 30 days and 60 days of transplanting

Wilts & Blights

1. 1. Fusarium Wilt (Fusarium oxysporum f.sp. lycopersici)

Wilt diseases are caused by pathogens that invade the vascular system (xylem tissue) and disrupt water flow through the plant. Fusarium wilt is the major wilt disease of tomato in Oklahoma. Verticillium wilt is easily confused with Fusarium wilt, but has not yet been reported in Oklahoma. The first symptom is usually a yellowing of the lower leaves, which gradually wilt and die. Symptoms may first occur on only one side of the plant (Figure). The disease progresses up the stem until all of the foliage is killed and the plant dies. If stems or petioles from wilted areas of diseased plants are cut, a reddish-brown discoloration can be seen between the pith (center of the stem) and the outer green part of the stem (Figure). The fungus survives and persists indefinitely in field soil. The fungus is also seedborne and is thought to spread long distances in this manner. The disease is most serious in sandy soils and at temperatures between 26-32 ℃. Soils become infested by planting infected transplants and from movement of infested soil by wind and water erosion or on farm implements.

Control: Growing tomato varieties resistant to Fusarium wilt is the most effective means of control. Improved varieties and hybrids are available that have resistance to races 1 and 2; and 1,2 and 3. Resistant varieties can become susceptible to Fusarium wilt through time when they are intensively cropped on the same site. For example race 3 has been reported in other states where tomatoes are intensively grown. Crop rotation should be used in conjunction with varietal resistance to maintain sustainable control and limit the development of new races.

1. 1. Southern Blight (Sclerotium rolfsii)

Southern blight can be a devastating disease of tomatoes in Oklahoma. The southern blight fungus has a wide host range attacking more than 200 species of plants that include common weeds and crop plants. The initial symptom of southern blight is a rapid wilting of the entire plant. A water-soaked lesion on the stem near the soil line rapidly expands, turns brown and girdles the stem. A white mold (mycelium) eventually covers the stem lesion and surrounding moist soil. Small, uniformly round structures about 1/16 inch in diameter (called sclerotia) form on the mycelium. Sclerotia are first white, later becoming brown, and resemble mustard seeds. The presence of the white mycelium and sclerotia at stem base of affected plants are very useful characteristics for identifying southern blight (Figure 3). The fungus survives in the soil as sclerotia, which may build to high numbers when susceptible plants are cropped repeatedly. After sclerotia germinate, the fungus must first colonize organic debris near the soil surface before the fungus can cause infection. The disease is favored by high humidity and soil moisture and warm to hot temperatures (29-35 ℃).

Control: Southern blight is difficult to control when conditions favor the disease and numbers of sclerotia in the soil are high. Crop rotation with a non-susceptible grass crop, such as corn, is the most effective means of reducing numbers of sclerotia and resulting incidence of southern blight. Avoid planting tomato following a very susceptible crop such as cantaloupe or watermelon. Plant residues should be thoroughly incorporated into the soil prior to transplanting so their presence on the soil surface does not encourage southern blight development. A fungicide program for southern blight may be beneficial.

Foliar Diseases

1. 1. Early Blight (Alternaria solani)

Early blight is a common leaf-spotting fungal disease of tomato. Extensive defoliation from early blight exposes fruit to sunscald and increases fruit rot. Early blight also attacks stems and fruit. Foliar diseases are most severe in eastern Oklahoma where rainfall and relative humidity levels support disease development, or wherever sprinkler irrigation is used. Dark brown cankers may develop on stems and girdle stems of seedlings at the soil line. Stem lesions on older plants usually remain confined to one side of the stem. Leaf symptoms appear on older leaves first and are characteristic of the disease. Infected leaves show circular spots (lesions) up to 1/2 inch in diameter that are brown and have a pattern of concentric rings imparting a “target-like” appearance to the spot (Figure). The leaf area surrounding these spots may turn yellow. Infected leaves eventually turn brown and drop from the plant. Defoliation progresses upward from the lower plant. Sunken, dry lesions occur most frequently on the stem end of the fruit and also have a zonate or “target-like” appearance. The fungus survives in the soil by forming resistant spores in association with diseased tomato debris capable of persisting for one year or more. Infection occurs rapidly under warm, humid conditions. Thousands of spores are produced in spots of infected leaves and are capable of causing more infections. Plants under stress from nitrogen deficiency, heavy fruit load or other factors are most susceptible to the disease.

Control: Crop rotation with crops other than eggplant, potato and pepper should be practiced to reduce and delay early blight development. Avoid prolonged wetting of leaves from irrigation or use drip irrigation. Maintain adequate, but not excessive, soil fertility. A spray program using a recommended fungicide beginning at fruit set and continuing on a 7- to 14-day schedule should be maintained where early blight problems are anticipated.

1. 1. Septoria Leaf Spot (Septoria lycopersici)

Septoria is a very common foliage disease in Oklahoma that may also attack stems, but not fruit. The disease first appears on the lower leaves after the plant has set fruit. Leaf spots begin as yellow areas that later become circular with gray centers and dark borders (Figure). Spots may reach 1/8 inch in diameter and be surrounded by a yellow halo. Tiny black specks may develop in the center of these spots. These are fruiting structures that release spores. Severely infected leaves fall off. Defoliation progresses from the base of the plant upwards and resembles early blight from a distance. However, the larger dark leaf spots with concentric rings of early blight are clearly different from smaller Septoria leaf spots. Loss of foliage may cause fruits to become sunscalded. Most infection early in the season probably arises from infested plant debris remaining in the soil from a previous tomato crop. Spores of the fungus are spread by splashing rain. The disease is favored by moderate temperatures and extended periods of high relative humidity.

Control: Crop rotation and thorough shredding and incorporation of infested plant residue soon after harvest are recommended to reduce Septoria leaf spot. Weed control should be maintained because jimsonweed, horse nettle and nightshade are also sources of infection. Drip is recommended to reduce periods of leaf wetness and water splashing. Sprinkler irrigation should not be used. Avoid working plants while foliage is wet. A fungicide spray program for early blight will also be effective for control of Septoria leaf spot.

1. 1. Gray Leaf Spot (Stemphyllium solani)

This is a disease confined entirely to the leaves of tomato. The oldest leaves are affected first. Symptoms first appear as small brownish-black flecks that extend to both sides of the leaf. Spots may be bordered by a narrow yellow halo. As the spots enlarge, the central portion becomes gray, cracks and falls out imparting a shot-hole appearance to affected leaves. The disease closely resembles Septoria leaf spot. Leaves with numerous spots turn yellow and drop to the ground. The fungus overwinters on infected plant residue. The disease is favored by warm temperatures, high humidity, heavy fruit loads and adequate levels of soil fertility.

Control: Many of the newer tomato varieties recommended for growth in Oklahoma are resistant to gray leaf spot. If a susceptible variety is grown, cultural and chemical controls are similar to those for early blight and Septoria leaf spot.

1. 1. Late Blight (Phytophthora infestans)

Late blight, an important potato disease, can also occur on tomato. The warm to hot temperatures prevailing in Oklahoma during periods of tomato production make the occurrence of this disease unlikely. However, the disease could be a potential problem during unseasonably cool and wet conditions on early-planted or fall-cropped tomatoes. All parts of the plant are affected and fruit decay can be severe. Symptoms appear on the upper surface of leaves as greasy, gray spots that expand rapidly when leaves are wet or humidity is high (Figure). White mold usually develops at the margins of affected areas. If stems and petioles are infected, areas above these infections wilt and die. Entire plants may be rapidly defoliated when conditions favor the disease. Fruit infections begin as brown, greasy spots that rapidly expand to rot the entire fruit. The fungus is a wet weather disease favored by cool nights and warm days. Temperatures above 30 ℃ are considered unfavorable for late blight development. The fungus survives mainly in potato seed tubers and in infected tomato transplants. Some survival may also occur in dead potato and tomato vines. The disease often begins in potato plants, from which spores of the fungus are blown by wind to infect tomatoes in favorable conditions. Disease development is rapid with extended periods of favorable conditions and ceases when weather becomes hot and dry.

Control: Late blight control centers on use of disease-free transplants and certified disease-free potato seed to avoid introduction of the disease. Tomatoes should be planted as far as possible from potatoes and potato cull piles. Dead vines from previous crops should be removed from the vicinity of new plantings or destroyed. Avoid use of sprinkler irrigation where possible. A fungicide spray program is required to control late blight.

Fruit Rots

1. 1. Anthracnose (Colletotrichum phomoides)

Anthracnose is a common and widespread rot of ripe or overripe tomato fruit. Symptoms are rare on green fruit. Symptoms on ripe fruit are small, sunken, circular spots that may increase in size up to 1/2 inch in diameter. The center of older spots later become blackish (Figure). Spots may become numerous in severe cases, and secondary rotting organisms may invade anthracnose lesions to completely rot infected fruit. The fungus forms small, dark survival structures called sclerotia in the centers of fruit spots. These sclerotia survive in soil for up to three years, and cause infections either directly or by producing secondary spores. Green fruit are infected but do not show symptoms until ripening. The fungus then spreads from infected to healthy fruit as spores are splashed by rain or overhead irrigation, or by pickers working wet plants. Anthracnose is favored by warm rainy weather, overhead irrigation and heavy defoliation from foliar disease.

Control: Harvest fruit as soon as possible after ripening. Avoid excessive overhead irrigation or use drip irrigation to reduce moisture levels on fruit and humidity in the plant canopy. Fungicide sprays used to control leaf diseases reduce losses from anthracnose when applied on a regular schedule and in a manner to achieve thorough fruit coverage. A three-year rotation may also reduce chances for infection.

Soil Rots

Soil rots are caused by several fungi which reside in soil and infect fruit in direct contact with the soil or are splashed into lower fruit near the soil. Warm, wet conditions and growth of tomatoes in poorly drained areas favor soil rot development. Ripe fruit is generally most vulnerable to soil rot development, however green fruit may also be affected.

1. 1. Buckeye rot (Phytophthora nicotinae)

Buckeye rot is a destructive fruit rot of green or ripe fruit. The first symptoms are grayish-green or brownish, watersoaked spots developing where fruit contact the soil or where soil frequently splashes onto fruit. When temperatures are warm (>26 ℃) the spot rapidly enlarges to cover up to half of the fruit diameter. The rot then appears brown with concentric rings that resemble the markings of a buckeye chestnut (Figure 8). The disease is most severe in poorly drained areas.

1. 1. Southern blight (Sclerotium rolfsii)

The southern blight fungus causes a sunken, yellowish lesion to develop where ripe fruit contact the surface of infested soil. The lesion enlarges to become star-shaped and watersoaked. The entire fruit collapses within 3 days to 4 days. A mass of white mold and developing sclerotia become evident on the lower side of rotted fruit.

1. 1. Pythium rot (Pythium spp.)

Pythium rot begins as a small water-soaked spot where the fruit contacts the soil. Within 72 hours, the entire fruit becomes rotted, the skin ruptures and the watery contents of the fruit spill out. A white, cottony growth may be observed within rotted areas of the fruit under humid conditions.

1. 1. Rhizoctonia soil rot (Rhizoctonia solani)

Rhizoctonia causes a brown rot with alternating light- and dark-colored zonate bands and sharply defined margins in areas where fruit contact soil. The rot may be firm at first, but later, affected fruit becomes mushy. Control: Tomatoes should be staked or otherwise held upright to minimize fruit contact with soil. Avoid planting tomatoes in poorly drained soils or in low areas of a field. Mulching with plastic film or with organic matter to keep fruit from contacting the soil and/or to reduce soil splashing onto fruit will reduce the chance of soil rot infection. A fungicide spray schedule for foliar disease control may also help reduce infection, provided coverage of the fruit is achieved.

Weed control

• There is need of light hoeing during first four weeks in the field which encourage the growth but also remove the weeds from the field. The surface soil is loosened by hand hoeing as soon as it is dry enough after every irrigation or shower. All weeds should also be removed in this process.
• Mulching with straw, black polythene and many other materials has been found beneficial in moisture conservation, in controlling weeds and some diseases.