Organic fertilization in nectarine (Prunus persica var. nucipersica) orchard combines nutrient management and pollution impact

Recycled organic fertilizers may be used to replace chemical source of nutrients; however, some nutrients such as nitrogen and heavy metals released by mineralization can become potential pollutants. The objective of this experiment was to compare, over a 3-year-period of time, the effectiveness of two organic fertilizers (cow manure and compost) with a traditional mineral fertilizer on soil fertility, tree nutritional status, heavy metal concentration in soil and plant in a mature nectarine orchard. Trees were subjected, since their plantation (made in 2001) to the following treatments: (1) mineral fertilization (including nitrogen at 130 kg ha-1 year-1); (2) cow manure (5 t DW year-1 ha-1); (3) compost (5 t DW year-1 ha-1). Soil organic matter and total nitrogen concentration increased as a consequence of compost application. Soil nitrate concentration was increased by mineral fertilizer and compost applications. In summer, macro and micro nutrient concentrations in leaves were not affected by treatments with the exception of N that was increased by mineral fertilization. At the end of the season, leaf N, K and Zn were remobilized to storage organs, while Ca, Mg, Cu, Fe and Mn accumulated in abscised leaves and returned to the soil, with no differences among treatments. Nitrogen and K were found principally in fruit flesh. With the exception of Cu and Zn, the concentration of heavy metals in leaves and fruits was below detection limits. Total and DTPA-extractable heavy metals in soil were not increased by organic fertilization if compared with mineral fertilizer