Correction of Manganese and Zinc Deficiencies, in Orange Trees

Bruno Razeto M.1, José Longueira M.1, Sylvia Rojas Z.1 y Gabino Reginato M.1

Manganese and zinc deficiencies, shown by 6 years old 'Thompson Navel' orange trees, were treated with foliar sprays of mangenese sulfate, zinc sulfate, and a mixture of both, either with or without urea addition to the solution. . The sprays were made on October 4, 1985 and repeated on November 22 of the same year. Each treatment was applied to five trees, in a randomized block designo Sprays with manganese sulfate or zinc sulfate corrected the deficiency symptoms only partially. Sprayings with a mixture of both salts eliminated the symptoms completely. The effect was evident one and a half months after the first application and reached its peak three months later. Thereafter, there was a gradual increase in the symptomatology, but the application benefit was still present one year and a half later. The sprays with each element separately determined a marked increase of its content in the leaves that received the chemical directly. Although with less intensity, this effect persisted in the leaves developed later on (during autumn), but only when each element was individually applied. This evidences the movement of both elements towards leaves formed much after the applications. Simultaneous sprays with both salts resulted in a lower increment of the level of each element in the sprayed leaves. However, adding urea to the mixture, made these levels rise to the one induced by the separate sprays. The control of these deficiencies, both separately and simultaneously, determined and increased crop load in the season following that of appl ications. The correction of zinc deficiency resulted in a larger fruit size, in the same application season.

1 Departamento de Producción Agrícola, Facultad de Ciencias Agrarias y Forestales, U. de Chile, Casilla 1004, Santiago, Chile.