Abstract
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.
Highlights
Many species of the genus Castanea are grown in several parts of the world for timber and/or edible nut production (Portela et al, 2007)
Since lime was incorporated with a single pass of a cultivator, without turning the soil, the effect was marked in the top soil layer and decreasing with depth
The principal species of Mn in soil solution is Mn2+, which may decrease 100-fold for each unit increase in pH, and is the main form as Mn is absorbed by plants (George et al, 2012; Havlin et al, 2014)
Summary
Many species of the genus Castanea are grown in several parts of the world for timber and/or edible nut production (Portela et al, 2007). Orchards are established with many more plants per hectare (trees spaced at 8 × 8 m or less) and the cropping system is intensified, with regular pruning, chemical fertilization, and mechanical harvesting, stimulated by the expectation of a high profit that the price of the nut may provide. There are limited scientific data on chestnut management, in particular in the field of mineral nutrition and crop fertilization (Portela et al, 2007). In the past, this species was not fertilized, the soil only being amended when farmyard manure was available. Studies done with young potted plants have shown that the crop responds to the application of mineral nutrients
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