Introduction: Planting date is one of the most influential factors in determining sugar beet yield and quality. Due to its effect on the length of plant growth period, i.e. the number of growth days received by the plant, planting date has a significant impact on crop yield and is one of the most influential and decisive factors in agricultural production. The selection of the harvest date is one of the pillars of vintage quality and sugar yield in sugar beets. However, it is difficult to define the harvest date and, more precisely, the maturity date of beet roots in a precise and absolute manner. Indeed, there are various stages and degrees of maturity based on environmental and climatic conditions such as temperature, precipitation, latitude, and others. Because sugar beet lacks a distinct physiological ripening stage, similar to cereals. Due to the effect of farm management, particularly the application of planting and harvesting dates, on the yield and quality of sugar beet, it is necessary to plan carefully in order to determine the optimal planting and harvesting dates for this crop in each region. Due to the risk of autumn frost and the necessity of transport planning to the sugar factory, farm management is crucial. On the basis of this information, the first harvest date should be determined, which has a suitable and acceptable yield of white sugar, and the product should be harvested and transported to the sugar factory as soon as possible.
Materials and Methods: To determine the effect of planting and harvesting dates on root yield and certain quality characteristics of sugar beet in the Bardsir region of Kerman province, a split -plot randomized complete block experiment with four replications was conducted. The main factor was the sowing date, which was applied at two levels: The first sowing date was April 21 and the second was June 5. The sub-factor was the harvesting date, which began on August 23 and occurred in nine stages with a 15-day interval in the relevant plots.
Results and Discussion: The results revealed that the sixth, seventh, eighth, and ninth harvesting dates in the first sowing date produced the highest root yield, and only in these four treatments the root yield reached more than 50 tons per hectare. The treatments of three first, second, and third harvest dates on the first sowing date and three fifth, sixth, and seventh harvest dates on the second sowing date produced the most nitrogen in the roots. The greatest amount of root molasses sugar was found in the first and second harvest dates on the second sowing date; in these treatments, the amount of root molasses sugar exceeded 5.8%. Also, the greatest amount of gross sugar was assigned to the fifth, sixth, seventh, eighth, and ninth harvests on the date of first sowing, and the amount of gross sugar in these five treatments exceeded 18%. In addition, the sixth, seventh, eighth, and ninth harvest dates had the highest white sugar yield on the first planting date. Due to the risk of autumn frosts and, on the other hand, transport planning to the sugar factory and farm management, it is necessary to harvest immediately if the desired white sugar yield is achieved.
Conclusion: According to the findings of this study, delay in planting sugar beet increased root impurities and decreased root sugar yield and percentage. Also, with the delay in harvesting for both planting dates, root impurities decreased and the proportion of crude sugar increased, resulting in a greater disparity between molasses and crude sugar and an increase in pure sugar. Due to the risk of autumn frosts and the need to transport the crop to the sugar factory, it is recommended that beet growers in this region plant on May 1 and harvest on November 15.