Effect of Boron, Potassium Sources and Rates on Soil Fertility, Sugar Beet Yield and Quality Cultivated in Saline Clay Soil in Egypt

Two field experiments were conducted at a private farm in El-QantaraSharq, Ismailia Governorate, Egypt, during the 2021/22 and 2022/23 winter growing seasons. The study aimed to assess the effect of boron and potassium sources and rates on sugar beet yield quality and soil fertility. The experiments were arranged in a split-split plot design. The main plots had foliar boron (B) application (without and with 4 g B/L), while the sub-main plots had potassium sources: K-sulfate, K-silicate, and K-humate. The sub-plots had potassium rates (0, 4, 8, and 12 g/L) applied as foliar spray at three intervals: 30, 45, and 75 days after planting. Results indicated that foliar boron application led to a 17.17% decrease in soil electrical conductivity (EC) compared to without boron spraying. However, there was no significant change in pH values. The study showed a significant increase in soil available N, P, K, Fe, Mn, Zn, and B with the application of 4 g/L of boron or K-humate at a rate of 12 g/L individually. Sugar beet yield, quality and root nutrients content were notably influenced by potassium sources in the following order: K-humate > K-silicate > K-sulfate. The interaction between boron spray and potassium sources and rates had a significant effect on various parameters, with the highest values for root length (cm), fresh root weight (kg/plant), root and top yield (t/ha), protein (%),sugar content (%) and sugar yield (t/ha) achieved by foliar application of boron combined with K-humate at a rate of 12 g/L.