Effect of potassium source and application rate on qualitative characteristics of sugar beet (Beta vulgaris L. cv. Aras) under full and deficit irrigation

To study the effect of potassium source and application rate on qualitative characteristics of sugar beet, a field experiment was conducted at county of Jovein, Khorasan Razavi, during 2010-2011. Experiment was carried out as split factorial in a randomized complete block design with three replications. Experimental factors included two irrigation regimes (full and deficit irrigation), two potassium sources (potassium sulfate and potassium chloride) and three potassium application rates (0, 50 and 100 kg K2O ha-1). Results showed that deficit irrigation increased sodium content of root by 16.8 percent compared with full irrigation. However, other qualitative characteristics of sugar beet were not influenced by irrigation treatments. Application of potassium chloride, increased root dry matter percent and decreased root nitrogen content compared with potassium sulfate. The sugar percent, white sugar percent, sugar purity and root alkalinity increased and molasses sugar percent, root potassium, sodium and nitrogen content decreased with increasing potassium application rate. The highest sugar percent (19.92), white sugar percent (17.96), sugar purity (90.70%) and root alkalinity (2.77) and also the lowest molasses sugar percent (1.82), root potassium (5.03 meq/100 g root) , sodium (1.35 meq/100 g root) and nitrogen content (2.39 meq/100 g root) were observed in 100 kg K2O ha-1 treatment. According to the results, in similar climatic conditions, the use of large amounts of potassium, particularly in the form of potassium chloride, is recommended for improving the qualitative characteristics of sugar beet under full and deficit irrigation conditions.