Boron deficiency in olive trees in Greece in relation to soil boron concentration

A survey was made in the areas of Greece where boron (B) deficiency has been recorded. Soil samples from various sites of Lesvos island, Attika, Messologi, Thesprotia, Preveza, Larissa, and Fthiotida were analysed for B by a number of methods currently in use. Boron content was also determined in olive leaf samples taken from the same sites and was correlated with the appearance or not of B deficiency symptoms as well as to soil B concentration. The results showed that B deficiency was localised in various places in Lesvos island and areas of Attika and Larissa. Typical B deficiency symptoms were observed, when leaf B concentration dropped below 15 mg kg(-1) dry matter. In many cases B deficiency in olive trees was not related with soil B concentration, but rather with soil depth. Boron concentration extracted by hot water, cold water, 0.01 M HCl, 0.05 M mannitol in 0.01 M CaCl2, hydroxylamine hydroxide, and ammonium oxalate was significantly correlated (P<0.001) with leaf B concentration. Critical B concentrations determined by these methods corresponding to deficient leaf B concentration were found to be 0.33, 0.17, 0.05, 0.41, and 0.14 mg kg(-1) soil for the methods using hot water, HCl, mannitol, hydroxylamine hydrochloride, and ammonium oxalate, respectively.