Nitrogen fertilization in apple trees. II. Foliar leveis, nutrient extraction and nitrogen use efficiency

Rafael Ruiz S.1

Based on a field experiment, on the response to N applications of Granny Smith and Richared Delicious apple trees, leaf analysis standards are proposed:

Granny Richared
Deficient < 1 .7 < 1 .9
Low 1 .7—1 .9 1.9—2.2
Adequate > 1.9 > 2.2

A posifive jnteraction was observed between N and Mg and Mn. Nitrogen applications depressed foliar K levels, dueto larger demands caused, especially, by higher fruit yields. In this orchard, under grass sod, N use efficiency was about 27%; N extraction increased from 37.7 to 70 kg/ha, in Granny Smith (fruits pluss pruned material); Kextraction increased upto 100 kg/ha; Mg extraction increase was, proportionally, the highest (3.8 to 8.3 kg/ha). Spur analysis showed a good diagnostic tool for apple trees.

1 Estación Experimental La Platina (INIA), Casilla 439, Correo 3,Santiago, Chile.