Tomato Agronomy Guide


Description

As a Solanaceae crop, tomatoes are related to peppers, eggplants, Irish potatoes and tobacco. Classified as a perennial, tomatoes can also be grown as an annual. Although tomatoes originate from South America, Mexico served as the first area to domesticate tomato varieties. In the U.S., tomatoes are grown more widely today than any other vegetable crop. Producers may sell tomatoes for fresh or processing uses. Tomatoes contain lycopene, which has antioxidant and anticarcinogenic properties. Additionally, they supply vitamins and minerals, such as vitamin C, vitamin A, B vitamins, potassium, iron and calcium.

Site Selection

To grow tomatoes, choose planting sites with deep, fertile upland soils or medium-textured bottomland soils. Tomatoes perform best in such areas. Sites with higher elevations may better handle earlier plantings because frost is more frequent in bottomlands. Ideally, the planting site would also have undergo previous cultivation or yearlong preparation. A well-prepared planting area will have limited competition from perennial grasses, weeds and woody vegetation. Soil pH level should range from 6.4 to 6.8. If pH ranges from 6.0 to 7.0, then blossom end rot would present a lower risk. Plant growth, nutrient availability and soil microorganism activity vary with different soil pH levels. The selected planting site needs to have not grown tomatoes for at least three years.

If planting tomatoes early, then the planting site may benefit from a windbreak that blunts damage caused by cold spring winds and enables plants to mature more quickly. With windbreaks, soil moisture is also conserved. Possible windbreaks include a hillside, tree row and rye strips planted in the field. Position tomato plantings near windbreaks to benefit most from the windbreak and realize the intended effects related to creating a microclimate. If using a windbreak crop, then insect control can present a problem if the crop hasn’t been killed before it would start dying back.

Tomatoes grow best when temperatures range from 60 degrees F to 90 degrees F. Growth, pollination and maturation may suffer when temperatures exceed 90 degrees F or drop lower than 55 degrees F. Designing raised beds will enable soil temperatures to increase more quickly. Raised beds also improve drainage but can be susceptible to water stress during dry periods. Typically, raised beds are constructed to be 3 inches to 8 inches tall.

Growers can also produce tomatoes in high tunnels, which are plastic-covered greenhouses that use solar heat and lack electrical or automated ventilation. High tunnels can elevate temperatures by 10 degrees F to 15 degrees F and lengthen the growing season. For example, using a high tunnel in central Missouri could enable planting tomatoes in March and maintaining tomato production until October. Some varieties may be removed from the high tunnel in July, but the high tunnel would still have use as a space for growing fall-crop peppers, cucumbers or beans. When choosing a high tunnel site, the area should be level and accessible, and it must drain well. Creating raised beds within the high tunnel can support drainage and warm the soil. Other possible elements used in high tunnel production include plastic mulch to warm the soil, drip irrigation to provide water and fertilizer, row covers to prevent frost damage and staking or caging. High tunnel size can vary. Dimensions can be as small as 10 feet wide, 9 feet high and 96 feet long or as large as 30 feet wide, 12 feet high and 100 feet long.

Fertility

Given that plant nutrition can affect fruit development, growers should conduct a soil test to determine fertilizer needs. Per acre, pre-planting fertilization needs are roughly 20 pounds of nitrogen, 40 pounds of phosphorus and 40 pounds of potassium. If using row beds or ridges, then apply fertilizer before the row bedding or ridging, and place it in the row about six inches deep. For level surfaces, fertilizer placement should occur from one week to two weeks after transplanting. Apply it about four inches deep and four inches to the side of the row. The soil should also contain at least 2.5 percent organic matter.

Later, sidedress nitrogen applications in a band that extends just past the plant foliage spread, or provide nitrogen using the irrigation system. When choosing nitrogen sources, calcium nitrate or ammonium nitrate are preferable. If sidedressing nitrogen, then apply 30 pounds per acre. The first sidedress application should occur when the first fruits measure 2-inch diameters. At three- to four-week intervals, continue the sidedress applications when foliage and vines appear healthy and productive. To know specific nutrient needs during the growing season, take tissue samples when plants begin to flower and green fruit begins to form, and analyze the results.

Variety Selection

When choosing tomato varieties, select those that don’t bear fruit that is too large, has green shoulders, cracks, matures late or can’t tolerate disease well. Other variety selection criteria include marketable yield potential, market acceptability, adaptability, maturity, shape, color, firmness and shipping quality.

University of Missouri Extension recommends the following hybrid tomato varieties for Missouri growers. These varieties are considered indeterminate and tend to not crack. They would require staking and trellising. Many other commercial tomato varieties, however, have the determinate characteristic, meaning that they grow like bushes and flower and bear fruit during a specific time period. Indeterminate varieties flower and bear fruit throughout their lives.

Recommended Tomato Varieties in Missouri

Name

Days to Maturity

Fruit Color

Fruit Size

Firmness

Avalanche

70

Red

Medium-large

Firm

Better Boy

70

Red

Medium-large

Firm

Conquest

70

Red

Medium +

Firm

Jet Star

72

Red

Medium

Firm

Pink Delight

70

Pink

Medium +

Firm

Show Me

70

Red

Medium-large

Very firm

Planting

Tomato production starts with transplants. Producers may grow transplants in house, but purchasing them from a reputable grower is an option for operations that lack the experience or facilities necessary for starting tomato plants. From an economic perspective, producers sourcing transplants from a commercial grower may have more viability than them growing their own transplants. Transplants available in containers tend to perform better than bare-root transplants. The best transplants have a sturdy, compact structure. When starting tomato transplants, plant seeds about 42 days to 56 days before transplanting.

Operators can adopt several strategies to reduce transplanting shock. Those include watering the plants shortly before transplanting; limiting plant exposure to direct sun and wind before planting; providing plants with about a half pint of a high-phosphate, water-soluble starter fertilizer at planting; firming the soil that surrounds tomato roots; and planting tomatoes at the correct depth.

Time the transplanting to occur when soil 3 inches deep has warmed to 60 degrees F. To plant tomatoes, make rows that have four- to five-foot spacing. Within a row, plant spacing should range from 18 inches to 36 inches. Plant populations per acre may typically range from 2,500 plants to 5,000 plants. However, if using double rows in plastic-covered beds, then the plant population may reach 10,000 plants per acre. Plant population and spacing needs may be different depending on the variety. For example, indeterminate varieties need more space because the plants grow larger. Because tomato plants will generate roots along stem surface buried below the soil surface, they can be planted deeper than they had grown in the container.

Cultural Management

To train tomatoes, possibilities include staking, constructing a wire-string trellis, developing a cage system or using the down or non-supportive system. Staking and trellising tend to be most popular. By stalking tomatoes or designing a string trellis, tomato plant foliage can remain upright, and fruit is less likely to touch the ground. If producers prefer staking, then insert wood or steel stakes to 10-inch depths and four inches to the tomato plant sides. To affix tomato vines to the stakes, choose a jute tomato twine, soft cord or other twine, and provide the plant with about 1 inch of give. Blossom clusters shouldn’t face the stake. Install the staking system two weeks to three weeks after transplanting. Staked tomatoes should be thinned to a single stem.

If training tomato vines with a trellis, then install 3- to 4-inch posts every 12 feet to 14 feet, and hang a 12-gauge wire across the top of the posts. Each post should have about five feet exposed. Use a 28-inch plant spacing when planting tomatoes in a wire-string trellis system. Attach a sturdy string from the tomato plant base to the wire string to form a V from the ground to the wire string. Thin the tomato plant to two stems, which will train on the twine.

Some varieties may need additional pruning. Determinate varieties, for example, may need plant suckers removed. With pruning, plants focus more resources on producing fruit. Producers should avoid pruning too heavily, however. With overpruning, tomato plants may record lower yields, and they may be susceptible to sunburn, blossom end rot and catfacing.

Water Management

Water needs vary throughout the tomato growing season. In May, tomatoes require 1 inch of water each week. Weekly water needs increase to 1.5 inches during June and September, and in July and August, water needs reach a maximum 2 inches per week. Using an irrigation system can ensure that water needs are met. Avoid administering too much water to tomatoes. When they have too much moisture available, tomatoes may have an increased cracking risk. Too much water during fruit set is especially problematic.

Weed Control

To control weeds, use cultivation, or apply herbicides. Other options include laying plastic mulch and adopting a crop rotation. Early cultivation may address mild weed infestations. If using cultivation, avoid disturbing the soil too deeply because root damage could result. Cultivating between tomato rows becomes more difficult when plants have grown large, and growing areas have had support structures installed. Pre-emergence herbicide applications can offer an alternative to cultivation at that point and limit hand labor requirements. Before planting, applying a pre-plant herbicide is an option. Herbicide use may be beneficial in growing areas not suitable for cultivation because of wet weather.

Insects and Diseases

Insects most likely to inflict damage in tomato crops are aphids, cutworms, flea beetles, hornworms, stink bugs, tomato fruit worms and spider mites. One week after transplanting, apply insecticides to manage these problematic pests. Later, apply insecticides as needed. Control tends to be effective with malathion and methoxychlor or carbaryl applications or diazinon applications. Producers should regularly scout fields to help plan insecticide application frequency and timing.

Three types of diseases can affect tomatoes: systemic diseases, foliar diseases and fruit diseases. Systemic diseases originate in the soil and later spread to harm the whole plant. Foliar diseases inhibit photosynthesis, and fruit diseases specifically target tomato fruit. Possible disease-related concerns for tomatoes include fusarium wilt, verticillium wilt, early blight, septoria leaf spot, gray leaf spot, anthracnose, tobacco (tomato) mosaic virus and nematodes. To control these issues, consider scheduling sprays at the appropriate time, eliminating weeds and maintaining good sanitation standards.

Fungicides can control disease risk. Within one week of transplanting, spray the fungicides for the first time. From that point, apply fungicides about weekly, and at least until harvesting the first tomatoes, continue those applications. Other disease control options include choosing resistant varieties, selecting an appropriate growing site and maintaining good transplanting and plant training practices.

Tomatoes are also susceptible to developing physiological disorders. Attributed to nutrition, water or environmental stresses, physiological disorders that may affect tomatoes include catfacing, leaf roll, flower drop and chemical injury. Blossom end rot is another tomato physiological disorder. Characterized as depressed, brown and somewhat dry rot, blossom end rot appears at the bottom, blossom end of a tomato, but it can be related to secondary infections that lead to total fruit rot. To control blossom end rot, address calcium deficiencies by using calcium nitrate if applying nitrogen. Also, supply even moisture to plants.

Harvest and Storage

When selling tomatoes locally, harvest when the fruit has turned pink or has entered the early red stage. To handle well yet still attract buyers, the fruit requires firmness and adequate color. If growing very firm tomatoes, then producers may delay harvest until the fruit has fully changed color. If selling tomatoes to wholesalers, then producers may need to harvest tomatoes when they’ve entered the mature-green to breaker stages. Cutting into a mature-green tomato will expose a jelly-like matrix and sufficiently developed seeds that don’t split from a sharp knife. At the breaker stage, the tomato’s blossom end has started turning pink.

For producers who choose to harvest tomatoes at the mature-green stage, they’ll only need to harvest fruit three or four times. For vine-ripened tomatoes, harvests are more frequent. As many as two harvests a week may be required.

Post-harvest work in tomato production can be significant and involve grading, cooling and packing tomatoes. When harvesting tomatoes, harvest and handling practices should avoid bruising the fruit. Ripe tomatoes would be more likely to bruise. Other possible mechanical damage to tomatoes includes cuts, punctures, scars, scuff marks and discoloration. To avoid damaging other tomatoes during packing and transportation, some producers remove the tomato stem after harvest.

Storage conditions will vary depending on the extent to which the fruit has matured and changed color. For tomatoes at the mature-green stage, they require storage temperatures that range from 55 degrees F to 60 degrees F. To optimize quality, storage life at 55 degrees F should be roughly two weeks because decay risk increases after that point. Light red tomatoes would ideally be stored at 50 degrees F to 55 degrees F. Firm-ripe tomato storage temperatures should range from 44 degrees F to 50 degrees F. When storing tomatoes, provide relative humidity levels from 90 percent to 95 percent. The high humidity helps to promote quality and minimize water loss. To encourage ripening, expose mature-green tomatoes to exogenous ethylene, which may have reduced effectiveness if carbon dioxide levels are too high. For cooling tomatoes, “forced air” units are preferred.

Sources

Coolong, Tim and George E. Boyhan. 2014. Commercial Tomato Production Handbook. University of Georgia. Athens, GA 30602.

Gaus, Arthur E., Henry F. DiCarlo and Chuck DeCourley. 1993. Fresh Market Tomatoes . University of Missouri Extension. Columbia, MO 65201.

Harper, Jayson and Michael Orzolek. 2006. Tomato Production. Penn State Extension. University Park, PA 16802.

Jett, Lewis W., David Coltrain, Jay Chism, James Quinn and Andrew Read. 2004. High Tunnel Tomato Production. University of Missouri. Columbia, MO 65201.

Kaiser, Cheryl and Matt Ernst. 2014. Field-grown Tomatoes. University of Kentucky. Lexington, KY40506.

Suslow, Trevor V. and Marita Cantwell. 2013. Tomato: Recommendations for Maintaining Postharvest Quality. University of California Davis. Davis, CA 95616.

Velandia, Margarita, Annette Wszelaki, Steve Bost, Frank A. Hale, Matthew Johnson and Becky Bowling. 2015. Sample Budget for Small-Scale Commercial Tomato Operations . University of Tennessee. Knoxville, TN 37996.