6. Foliar Diagnosis and Fertiliser Prescription in Forestry—The DRIS System and its Potential

Abstract

SYNOPSIS Problems associated with current foliar diagnosis techniques are reviewed. Many of these problems have been overcome in agricultural crops by use of the Diagnosis and Recommendation Integrated System (ORIS). The foundation of DRIS is the concept of nutrient balance, the interrelationships among all nutrients being considered simultaneously. The four steps required for the application of DRIS are described, viz (1) the data bank, (2) DRIS norms, (3) DRIS indices and (4) the testing of the norms. The advantages of DRIS over the critical levels approach are described by means of examples in agricultural crops. In forestry DRIS has been tested on a small-scale, investigative basis only. Four such attempts are reviewed. In the light of increasing evidence of the usefulness of DRIS in many crops, there is an urgent need for a thorough test of the system in forestry on a large enough scale.