Sugarbeet (Beta vulgaris) provides about 16 percent of the world's sugar production. Present world production is about 234 million tons of beets from about 5.9 million ha.(FAOSTAT, 2001).
The crop is believed to originate from Asia. Sugarbeet is a biennial crop but for sugar production beets are harvested in the first year. Flowering occurs during the second year. The crop is grown under rainfed conditions but also widely under irrigation in the subtropics where the crop is known for its high tolerance to saline and alkali soils.
The crop needs a relatively long growing period, normally from 140 to 160 up to 200 days. Large amounts of sugar are formed in the leaves. The greater part is used for growth processes during the vegetative period, while in the late growing period when vegetative growth slows down a large part is stored in the roots. However, sugar yield is determined by both root size and sugar concentration. With rapid growth of the storage root the sugar concentration reaches a steady value which is principally determined by climate, water supply and nitrogen level in the soil and is influenced to some extent by variety and plant spacing. Sugar percentage in the root is often greater than 15 percent of the fresh root weight. The crop is harvested toward the end of the first season's growth, when the roots contain maximum amount of sugar.
The crop is grown in different climates. Seed germination is possible at 5°C but the effective minimum is considered to be 7 to 10°C. Higher temperatures during vegetative growth are preferred, but high sugar yields are obtained when night temperatures are between 15 and 20°C and day temperatures between 20 and 25°C during the latter part of the growing period. During this period temperatures greater than 30°C greatly decrease sugar yields. For high sugar yields and low vegetative growth in the latter part of the growing period, progressively cooler nights should be accompanied by an exhaustion of available soil nitrogen and soil water.
When the crop is grown for seed, several weeks at low temperatures, near 4°C, are required to induce flowering, which tends to be accelerated by long days.
The crop can be grown on a wide range of soils with medium to slightly heavy textured, well-drained soils preferred. Restricted deep root growth in the early part of the growing period due to soil compaction may result in formation of forked and sprangled roots with reduced yields. Soil pH smaller than 5.5 is unfavourable to growth. Crust forming at the soil surface at the time of germination can lead to poor crop stand.
Adequate nitrogen is required to ensure early maximum vegetative growth. Nitrogen is often given in split applications, a small amount at planting and the rest after thinning. Nitrogen either in an excessive amount or when applied late during the growing season reduces sugar content. Fertilizer applications may be up to 150kg/ha N, 50 to 70kg/ha P at planting and 100 to 160kg/ha K.
A deep, well-prepared seedbed is advantageous. Seeds are planted 1 to 2 cm deep in single or double rows, with width between single rows 0.5 to 0.7m and double rows about 1m. When the plant has 4 to 8 leaves, thinning, by hand or by machine, is frequently needed to space 3 to 6 beets per metre row. Seed rates vary between 12 and 30kg/ha. Plant densities under commercial production vary from 40 000 up to 100 000 plants/ha.
Except during the early stages, after crop establishment, the crop is tolerant to salinity. Yield decrease is 0% at ECe 7, 10% at 8.7, 25% at 11, 50% at 15 and 100% at ECe 24 mmhos/cm. During early growth ECe should not exceed 3 mmhos/cm.
The graph below depicts the crop stages of sugarbeet, and the table summarises the main crop coefficients used for water management.