Evaluation of nutrients removed and recycled in a commercial peach orchard over a 14-years-production cycle

Understanding nutrient dynamics within a peach orchard is fundamental to the development of accurate nutrient management practices. The present study investigated the nutrient uptake and redistribution in a 14-years-old commercial orchard in the Po valley. At the end of the experiment, trees were harvested, biomass and organ nutrient concentration were determined. Skeleton and roots accounted for the highest plant biomass, followed by fruits at harvest, pruned wood and abscised leaves; thinned fruits were less than 1 kg tree-1. The difference between the amounts of nutrients in leaves sampled in summer and in autumn (at abscission) was used to estimate the fraction of nutrients remobilized during the vegetative season inside the tree. The decrease of N, P, S, Cu, Mn and Zn concentration in abscised, compared to summer-sampled leaves was the result of the translocation of nutrients into fruits and storage organs. Nutrient circulation in a commercial nectarine orchard was calculated by determination of the fractions of each nutrient recycled (sum of nutrients in abscised leaves, thinned fruits and pruned wood) and remobilized (sum of nutrients in fruits at harvest, roots and skeleton). In our experimental conditions, on average, nectarine Stark RedGold showed an annual request of (in kg ha-1) 100, 17, 73, 129, 16, and 6 of N, P, K, Ca, Mg and S, respectively. More than half of these quantities were recycled in the orchard and returned back to the soil; consequently, if the nutrient use efficiency is maximized, the fertilization of nectarine requires only small amount of external inputs.