Foliar colour as indicator of nutrient status of Scots pine (Pinus sylvestris L.) on peatlands

Foliar colour of Scots pine was measured using a chromameter from 85 fresh, dried or dried and ground foliage samples. The colours obtained in the XYZ notation were transformed into the Munsell notation (Hue, Value, Chroma). Foliar nutrient concentrations (N, P, K, Mg, Ca, Mn, Fe, Zn and B) of the needle samples were analysed. Suitability of foliar colour in the evaluation of the nutritional status of Scots pine stands growing on unfertilized peatlands was investigated using correlation and discriminant analysis. An independent data set (41 samples) containing also PK-fertilized stands was used to test the discriminant functions. The correlations between colour attributes and foliar nutrient concentrations were at their highest when colour was measured from the tips of fresh needles. Then the Hue of the needle tip turned greener with increase in the concentration of foliar K. The indicative value of the colour of dried needles in estimating nutrient concentrations and deficiencies was lower than that of fresh or ground needles; this was attributed to decrease in the variation of the colour attributes following drying. The colour of fresh needle tips was the best indicator of simultaneous deficiency of P and K, while deficiencies of N and B were not successfully detected. The Hue of the fresh needle tips that was yellower than 1.5 GY indicated simultaneous deficiency of P and K. However, in the case of fertilized stands, foliar colour had low diagnostig value.