Multivariate diagnosis of nutritional status of a crop and recommendation of elementary contributions to perform for optimizing the nutritional status, comprises removing dry material of aerial parts and determining their n elementary histological grades (X) in macronutrients and/or nutritional trace elements, establishing normal histological grades (x n) for each n considered nutrient elements, calculating nutritional indices (Ix n), with respect to n normal values (x n), to each n nutrient elements, and establishing basic histological grades for each nutrients. Multivariate diagnosis of nutritional status of a crop and recommendation of elementary contributions to perform for optimizing the nutritional status, comprises removing dry material of aerial parts and determining their n elementary histological grades (X) in macronutrients consisting of nitrogen, phosphorous, potassium, calcium, magnesium, sulfur and/or sodium and/or in nutritional trace elements consisting of iron, manganese, zinc, copper, boron,
