Abstract
In vineyards, if phosphate is applied both before planting and at intervals during growth without consideration of technical criteria, the soil P fractions may be increased and their proportions altered. This study was carried out to evaluate the accumulation of P fractions and the parameters of the adsorption isotherm in a sandy Typic Hapludalf soil in vineyards with a history of successive and excessive phosphate fertilization. In December 2010, two vineyards were selected, one 4 and the other 15 years old, in Urussanga, State of Santa Catarina (Brazil). Three trenches were dug in each area and soil was collected from the 0-5, 5-10 and 10-20 cm depth ranges. The soil samples were dried in a forced-air oven, sieved and subjected to chemical analyses, P chemical fractionation and P adsorption isotherms. Excessive phosphate fertilization, before and during cultivation, particularly in the older vineyard and, consequently, with a longer history of phosphate fertilization, increased the inorganic P concentrations to the depth of 20 cm, especially in labile fractions extracted by anion exchange resin and NaHCO3 in the non-labile fraction, as well as in the non-labile fraction extracted by 1.0 mol L-1 HCl. The application of phosphate fertilizers and the long cultivation period increased the P levels in the organic labile fraction extracted by 0.5 mol L-1 NaHCO3, and especially in the moderately labile fraction extracted by 0.1 and 0.5 mol L-1 NaOH. Phosphate fertilization of older vineyards, i.e., cultivated for 15 years, increased the amounts of P desorbed in water, indicating a risk of contamination of surface waters and groundwater. The phosphate fertilization before planting, without considering the results of soil analysis, and during cultivation, disregarding the results of soil analysis, leaf analysis and expected yield, led to a reduction in the maximum P adsorption capacity in the 0-5 cm layer of vineyard 2, indicating saturation of part of the reactive particle adsorption sites.
Highlights
The State of Santa Catarina has the fifth largest area of grapevine cultivation in Brazil, with approximately 5,000 hectares (IBGE, 2011)
In the soil of the 4-year-old vineyard 1, the contents of inorganic P extracted by anion exchange resin (AER) and of inorganic P extracted by 0.5 mol L-1 NaHCO3 were highest in the 0-5 cm layer (Table 2)
In vineyard 2, the highest inorganic P contents extracted by AER were found in the 5-10 cm layer, and the highest inorganic P contents extracted by 0.5 mol L-1 NaHCO3 in the 0-5 cm layer
Summary
The State of Santa Catarina has the fifth largest area of grapevine cultivation in Brazil, with approximately 5,000 hectares (IBGE, 2011). In this state, the first vineyards were planted by Italian immigrants in 1873, in soils near the sea, with a sandy texture and predominance of 1:1 clay, low contents of organic matter and acids, and low natural fertility. After planting the vineyard, when soil analysis indicates the need, additional lime is applied to the soil surface during the vine cycle, without incorporation. Especially based on the results of leaf analysis and yield expectation (CQFSRS/SC, 2004; Brunetto et al, 2009), N, P and K are applied on the soil surface without incorporation (maintenance fertilization). The applied nutrients, especially P, are not always determined by technical criteria and, as a result, a buildup of this element in the upper soil layers and saturation of adsorption sites of the reactive particles in soil may occur over the years (Korboulewsky et al, 2002; Gatiboni et al, 2008)
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