Diagnosing the nutritional condition of chestnut groves by soil and leaf analyses

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 Braganca, 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 Braganca, 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.