WINTER RYE UPTAKE OF N-15 LABELED NITRATE AND AMMONIUM FROM THE SUBSOIL - FIELD EXPERIMENTS

A field experiment on winter rye was conducted over three years to study the effect of ((NH4)-N-15)2SO4 and (NaNO2)-N-15 applied at 40, 60 and 80 cm depths on crop N uptake during the growing period. N uptake was clearly influenced by the depth of N application. From 40 cm depth most of the fertilizer N was extracted at tillering and shooting, from 60 cm at shooting and from 80 cm only towards the end of shooting. The efficiency of the N applied to the subsoil ranged between 28 and 82 % which is similar to that of common N application.