The world-wide knowledge on citrus fertirrigation comes from the Mediterranean climate in soils originated from calcareous substrate, in which the acidification is pointed out as one of the fertirrigation advantages. On the other hand, the acidification on tropical soils has been a limiting factor, because it can compromise the fertirrigation system sustainability. Therefore, this research project was carried out in order to study the ion dynamics into the soil profile, to quantify the nutrient losses by leaching and its effects on the soil acidification on different nutritional programs, such as solid fertilization and fertirrigation. The field trial was set up in a Hapludult soil in a block of Natal sweet orange on Rangpur lime rootstock, in Pirajuí, State of Sao Paulo- Brazil, and carried out during three years. The treatments were consisted by two N, P and K rates (200-40-160 kg ha-1 and half) and three applying forms (solid fertilizers without irrigation, solid fertilizers irrigated and fertirrigation) summing up six treatments. The dynamics of ions in the soil was monitored by a soil samples taken at 0-20, 20-40 and 40-60 cm depth, and by soil solution samples taken, through the vacuum soil solution extractors at 30 and 60 cm depths. The highest ion concentrations in the soil solution occurred in the fertirrigated treatments, consequently these treatments were the ones which presented the highest electrical conductivity values. High concentration of N-NH4 and N-NO3 was observed in the fertirrigated treatment, compared to dry fertilizer treatments, demonstrating that there is limitation to nitrification and high potential for nitrogen losses by leaching. The continuous soil bases losses, observed in the fertirrigated treatments, promoted intense soil acidification which can compromise the fertirrigation sustainability in tropical soil.
citrus fertirrigation; dynamic of ions; soil acidity
