Effect of foliar nutrition on peach (Prunus persica L. Batsch) yield and fruit quality as related to different crop loads

The peach market is suffering an economic crisis mostly due to the gap between supply and demand. The improvement of fruit quality seems the most important aspect to focus on for producers and researchers. Today foliar nutrition is a common standard technique in fruit trees fertilization and thinning is considered necessary in peach culture. Several researches deal with the real efficiency of foliar nutrition for peach, but not with its effect on fruit quality and yield as related to different crop loads. The present experiment lasted two years and involved 40 fiveyear-old trees of cv. Corleonese trained to Y system and spaced 5 x 2.5 m, grown in the inland of Sicily (37° 41' N 13° 58' E). In the 40 trees the crop load effect was evaluated for 5 productive levels: at thinning time, the fruits were spaced to leave one fruit every 0 (non-thinned), 15, 25, 35 and 45 cm along the one year old shoot. For each productive level, 8 trees were randomly selected. Half of these trees for each productive level were weekly applied with foliar nutrition from 45 to 107 days after full bloom and the 20 remaining ones were left as control. The date of the last treatment was 15 days before harvest. The commercial products used for foliar nutrition were Alga Cifo and Floral 20 20 20. The quantity supplied for each treatment (20 trees) was 400 ml of Alga Cifo and 300 g of Floral 20 20 20 for 100 L of water. The total quantity of mineral nutrients supplied to each tree was: 16 g N, 7 g P, 13 g K, 0.2 g Fe, 0.1 g Mn, 0.01 g Cu, 5 × 10-3 g B, 1 × 10-2 g Zn, 4 × 10-3 g Mo. The fruit quality was improved with significant differences in fruit total acidity, pH, soluble solids concentration and surface red colour.