European chestnut is the most important cash crop in the highlands of NE Portugal. However, limited data on cropping
technique are available to help farmers make decisions. This work is motivated by the lack of data related to chestnut response to fertilizer
application. It reports results from a field fertilization trial consisting of the application of a combination of lime (L), nitrogen (N),
phosphorus (P), potassium (K), and boron (B), namely LNPKB, NPKB, –NPKB, N–PKB, NP–KB, and NPK–B. Seedlings of chestnut
were planted in June 2013 and grown for four growing seasons. Plant height, trunk diameter, and pruning wood were assessed every
year and used as indicators of tree crop growth. Elemental leaf analysis and other tools [SPAD-502 chlorophyll meter; Field Scout CM
1000 NDVI (normalized difference vegetation index) meter, and the OS-30p+ fluorometer] were used to assess plant nutritional stresses.
In January 2017 soil samples were collected at three depths (0–5, 5–10, and 10–20 cm) to determine several soil fertility parameters.
The nonapplication of K and B reduced the tree crop growth and pruning residues. Leaf analysis revealed leaf K and B concentrations
respectively in the NP–KB and NPK–B treatments to be in the deficient range previously established for chestnut. SPAD readings and
NDVI detected the reduced availability of N associated with the –NPKB treatment but not the reduced plant growth associated with
NP–KB or NPK–B treatments. The dark adaptation protocols of FV/FM, FV/F0, and OJIP measurements performed with the OS-30p+
fluorometer failed to diagnose the nutrient stresses detected by leaf analysis or the reduction in plant growth.
