Foliar Levels of Potassium in Relation to Potassium Deficiency Symptoms in Radiata Pine

Abstract

SUMMARY Potassium deficiency symptoms appear in radiata pine (P. radiata D.Don) in spring and usually disappear in other seasons. They are most noticeable behind the new shoots in the later needles of the previous year's growth. Later needles were 6.3 per cent lower in potassium than other needles of the same year. Levels of potassium below 0.35 per cent in the later foliage of age 0 to 1 year in the upper lateral branches were associated with smaller than normal increments of height, diameter, basal area and volume in field plots. Potassium content was low also in foliage close to newly developing shoots of trees which had sufficient nutrients and showed no deficiency symptoms, and also in the late needles of older foliage. Other far larger variations encountered in routine sampling of foliage for potassium are evaluated and their errors are discussed. Sampling criteria and levels of fertiliser addition to plantations are suggested.