The objective of the present study was to investigate the effect of potassium rock (from the Eastern Desert of Egypt) and K-spraying as alternative potassium sources for the common potassium fertilizer in the presence of boron on sugar beet yield and juice quality. Two field experiments were carried out at Sakha Agricultural Research Station Farm during two winter seasons of 2007/2008 and 2008/2009. Split plot design was used with four replicates. The main plots assigned with two boron treatments: (1) without boron fertilization, and (2) spraying with boron solution two times (2.4 kg boric acid ha-1). The sub-plots were assigned with six potassium treatments: (1) without potassium fertilization, (2) application of 115 kg K2O ha-1 as potassium sulphate 48%, (3) application of 57 kg K2O ha-1 as potassium sulphate, (4) application of 115 kg K2O ha-1 as K-rock (7.5% K2O), (5) application of 57 kg K2O ha-1 as K-rock and (6) spraying with potassium 40% K2O(4.8 Lha-1). The obtained results can be summarized as:
Boron fertilization led to increase root yield by 15.6 and 13.9% in the first and second season, respectively and increased top yield by 33.6 and 38.1%, increased white sugar by 16.2 and 15.2%, increased sodium%, potassium%, quality % in the root, nitrogen % and K% in the leaves. The response to boron was less under K-rock source. It also increased sugar beet root and top yields. The highest root and white sugar yields were obtained with the K-rock. K-spraying had the high top yield and root and sugar yields under boron fertilization.
Potassium fertilization increased N, P and K% in the leaves, N and K in the roots and decreased available N in the soil after harvesting.
The obtained results showed that K-rock was the best source of potassium are present in Egypt. K-spraying in the suitable stage (critical periods) is a good helpful tool in correcting K-insufficiency.