Review of agronomical calendar research on sugar beet in Iran

Sowing and harvesting date are the most important agronomic factors that we should pay attention to proper date selection for sowing date in order to achieve good crop establishment and to harvest date in order to achieve the best time for crop quantities and qualities ripening. Farmers intend to germinate sugar beet seed at minimum environmental temperature. Sowing date affects crop canopy development (leaf number, size and age) in relation to absorbed radiation during growing season. Sugar beet can get optimum leaf area and use solar radiation effectively and will have more yields if it is planted as soon as possible. Cold condition in spring sowing may limit germination and establishment and cause bolting. Wet soil in this sowing may prevent on time sowing and crop couldn’t use solar radiation properly in this way. Early sowing may also decrease sugar content in most regions. On the other hand, delayed sowing till May will decrease germination because of soil dehydration and crusting during seedbed preparation. So, attention to selection of proper sowing date is necessary. Results of spring sugar beet sowing experiments show that we can sow at first possible time after hard winter coldness when soil mean temperature is about 3-5 °C. Freezing damage risk will decrease in this case and also irrigation isn’t necessary because of soil moisture and first season rains but we should irrigate land for better crop establishment at the first possible time if raining doesn’t happen. Early sowing will also increase white sugar yield in most experiments and insect damages will decrease because crop is at a growth stage which is not affected by initial insect attack. Some diseases such as Curly top and Rhizomania will decrease in early sowing. Some researches showed maximum Curly top damage in early season, while white sugar yield was high. The best sowing time is between March and last April in different areas in order to achieve the highest root and white sugar yields. Sugar beet can be harvested 180-210 days after sowing in most areas of Iran. The best harvest time based on research is between last October and first November for maximum white sugar yield. The best sowing date is between September and first October for warm and autumn sowing areas in the country. In spite of bolting decrease in delayed sowing, white sugar yield decreases significantly. The best harvesting time is between May and first June in which root yield and sugar content are high but bolted varieties increase also. So, we can use bolting resistant varieties and sow them in October and harvest them at June in Khuzestan.