SPAD index for diagnosing nitrogen status and oil yield in 'Arbequina' olive trees

Abstract

The objective of this work was to evaluate the technical feasibility of SPAD index to estimate the N status and the oil yield of olive trees 'Arbequina'. The experiment was carried out in field conditions, over five consecutive production cycles in Southern Brazil. Treatments consisted of five doses of N applied to the soil (0, 30, 60, 90, and 120 kg ha^-1 of N) split into two applications. In the second half of January, which is the standard leaf-sampling period, SPAD-502 chlorophyll meter readings were performed on 20 leaves per plot, together with the collection of samples for leaf-N determination. Effects of all N doses applied to the soil were observed for SPAD index and leaf-N content, showing a positive linear correlation. Olive oil yield showed a negative correlation with the SPAD index and foliar N content in the laboratory. The SPAD index can be used in January for the nutritional diagnosis of N in 'Arbequina' olive trees with readings between 88 and 130, which falls within the range of nutrient levels considered adequate to provide satisfactory plant growth and productivity for agronomic interpretation.