Crop Establishment

Plant Populations and Crop Spacing

A rule of thumb for soil and bag culture is that each plant needs 0.4 m² growing area and that total plant density should be 24,710 plants ha^-1. Generally, tomatoes in peat bag culture are set out in double rows, with centers about 1.2 m apart and 0.35-0.40 m between plants. Although closer cropping may increase yields per ha slightly, and are sometimes used in areas with very high light and on rockwool systems, yield per plant generally decreases, while diseases and pests, and labor per unit of fruit harvested increase.

Planting and Cropping Schedules
The tomato plant is a short-lived perennial and can be maintained for periods of a year or more in favorable environments. Long-season cropping allows markets to be served for most of the year. Whatever the cropping schedule, most production schedules allow at least a month between crops for clean-up and disinfection. The time chosen to be out of production is usually based on unfavorable prices or environmental conditions. Northern latitude growers may shut down or shift to other crops midwinter because of the high cost of heating and slow growth. Southern latitude growers may avoid mid-summer production because of the high costs of cooling, poor fruitset and fruit quality and competition from field tomatoes. In some cases, especially in the southeastern US, separate fall and spring crops are grown and production breaks occur both mid-winter and midsummer. Where both fall and spring crops are grown, a separate transplant production house reduces carry-over of pest and diseases. Additional advantages of a transplant house are the ability to maintain different temperatures, and add supplemental lighting or CO₂ enrichment. If only a single crop is grown, it usually starts either late summer or late fall and lasts until early summer.

There are many variations of cropping schedule, however. The plant grows most vigorously and is most productive in its first 6 months of growth, and pest, disease and other types of damage all increase as the plant ages. The Rutgers single truss tomato production system takes maximal advantage of high early-season productivity and maintains continuous production by replacing ‘old’ plants with new plants after a single cluster is harvested. This method is currently utilized in a 0.4 ha range in Burlington County, NJ, USA (Fig. 7). Labor and plant establishment costs are high with this system, however. Another cropping system is to remove leaves all the way up to 1.2 m from the top of existing plants and then raise the plant up to the wire. This greatly increases light penetration to the bottom of the canopy (Fig. 8). Young plants are then placed next to the existing plants in the row for the last month or so of a 6 month cropping cycle.