Liming and application of nitrogen, phosphorus, potassium, and boron on a young plantation of chestnut

Abstract

European chestnut is the most important cash crop in the highlands of NE Portugal. However, limited data on croppingtechnique are available to help farmers make decisions. This work is motivated by the lack of data related to chestnut response to fertilizerapplication. 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 chestnutwere planted in June 2013 and grown for four growing seasons. Plant height, trunk diameter, and pruning wood were assessed everyyear and used as indicators of tree crop growth. Elemental leaf analysis and other tools [SPAD-502 chlorophyll meter; Field Scout CM1000 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 concentrationsrespectively in the NP–KB and NPK–B treatments to be in the deficient range previously established for chestnut. SPAD readings andNDVI detected the reduced availability of N associated with the –NPKB treatment but not the reduced plant growth associated withNP–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.