Can foliar application modify nutritional status and improve fruit quality results on apple in Northeastern Italy

Optimizing fruit production and fruit quality by manipulating fertilizer supply is difficult but can be successfully done. Most studies in central Europe have focused on timing and rates of soil-applied fertilizer; little data are available concerning foliar nutrient applications and their effect on fruit quality. Calcium, K, and N concentrations in fruit, and K/Ca or N/Ca concentration ratios are related to fruit quality. Preharvest Ca spray treatments have been successfully used to maintain the postharvest quality of apples by increasing mean fruit Ca concentration and by decreasing the K/Ca ratio. We conducted a field study to evaluate the effectiveness of Medagro foliar nutrient products that are claimed to be both highly phytoavailable and compatible with pesticides. The experiment was initiated in 2000 in a ‘Golden Delicious’ clone B/M9 apple orchard at Olle in the Valsugana of northeastern Italy. Three treatments were imposed: no soil and foliar fertilization (Control); soil fertilization (Soil Only); soil and foliar fertilization (Soil + Foliar). Both fertilization treatments increased mid-summer leaf green color and concentrations of N, K and Fe, but reduced leaf P, Mg and B concentrations relative to the Control. The Soil + Foliar treatment had higher leaf Ca, Fe, Mn and Zn concentrations than the other treatments. The Soil + Foliar treatment consistently produced higher fruit Ca, Mg, Fe, Mn, and Zn concentrations, and lower B concentrations, than the Control treatment at harvest and after four months of storage. Inclusion of the foliar sprays increased fruit concentration of some elements relative to the Soil Only treatment at one or both fruit sampling times. The Soil + Foliar treatment improved fruit size distribution and reduced the incidences of bitter pit and rots relative to the other treatments. The results confirm that foliar nutritional sprays can be a useful management practice to enhance fruit nutrient status and consequent fruit quality.