Determination of leaf standards for mineral diagnosis in pear orchards in the Po Valley, Italy
2002
Toselli, M. | Mazzanti, F. | Marangoni, B. | Tagliavini, M. | Scudellari, D.
Leaf analysis is a tool to evaluate tree nutritional status, however its reliability depends upon the availability of proved indices, established in the same area of diagnosis, against which to compare the results of leaf mineral analysis. The early knowledge of optimal mineral leaf concentration can be helpful to adjust the mineral supply rate to tree requirement. The present study aimed to determine leaf standard indices for diagnosis of mineral status of pear orchards for two main pear cultivars, Abbé Fétel and Conference, grown in the eastern Po Valley (Emilia-Romagna), the Italian leading pear industry area. The 3-year long investigation was carried out on mature, commercial orchards with an history of constant and satisfactory yields and fruit quality. The orchards were located on sub-alkaline, moderately calcareous soils with a clay-loamy to loamy texture. Leaf samples (50 leaves) were collected at petal drop, fruit set (40-45 days after petal drop), and mid-July. Spur leaves were analyzed at petal drop, while fully expanded leaves inserted in the apical third of the shoot were analyzed at fruit set and mid-July. Leaf N, P and K concentration decreased over the season, Ca increased, while Mg was steady. A high concentration and variability were observed for Mn, Zn and Cu analyzed at petal drop, as a result of spring pesticide sprays. In mid-July, Ca leaf concentration was higher while K was lower in 'Conference' than in 'Abbé Fétel'; N, P and Mg were similar in the two varieties investigated. In mid-July, for 'Abbé Fétel' we established the following optimum leaf concentrations: N = 2.00-2.45; P = 0.14-0.20; K = 0.80-1.50; Ca = 1.10-1.90; Mg = 0.35-0.50. For 'Conference' the optimal leaf concentrations were: N = 2.00-2.40; P = 0.12-0.18; K = 0.75-1.30; Ca = 1.45-2.40; Mg = 0.30-0.40.
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