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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. [ABSTRACT FROM AUTHOR]

Chestnuts have always been a marginal fruit crop, and the trees seldom fertilized as a result. Few studies have been devoted to the management of soil fertility and the nutritional status of this crop. This work reports results of soil and plant analyses of a population of respectively 1041 and 198 soil and leaf samples taken across nine municipalities in the district of Bragança, NE Portugal. A second population of 80 soil, leaf and fruit (only 64) samples were taken across the three most productive municipalities in the district of Bragança, from the same orchards, to allow the establishment of relationships between soil fertility parameters and the nutritional status of the trees. The results of the two soil populations showed high soil acidity, low organic matter content, low phosphorus and high potassium content. A high percentage of leaf samples showed concentrations of nutrients below the lower limit of the sufficiency range in both the first and second sample populations, for nitrogen (respectively 63 and 47%), phosphorus (18 and 15%), potassium (34 and 31%), calcium (19 and 52%), magnesium (21 and 13%) and boron (40 and 43%). In the case of boron, 6 and 8% of leaf samples of the first and second populations displayed values within the excessive concentration range. The results of this work also revealed absence or poor relationships between soil properties and/or soil available nutrients and leaf concentration of nutrients. In this crop, therefore, it seems necessary to start applying regular fertilization programs, mainly based on regular evaluation of the nutritional status of trees through leaf analysis. [ABSTRACT FROM AUTHOR]