Organic and nitrogen fertilization of soil under Syrah grapevine: effects on soil chemical properties and nitrate concentration.

Viticulture is an activity of great social and economic importance in the lower-middle region of the São Francisco River valley in northeastern Brazil. In this region, the fertility of soils under vineyards is generally poor. To assess the effects of organic and nitrogen fertilization on chemical properties and nitrate concentrations in an Argissolo Vermelho-Amarelo (Typic Plinthustalf), a field experiment was carried out in Petrolina, Pernambuco, on Syrah grapevines. Treatments consisted of two rates of organic fertilizer (0 and 30 m3 ha-1) and five N rates (0, 10, 20, 40, and 80 kg ha-1), in a randomized block design arranged in split plots, with five replications. The organic fertilizer levels represented the main plots and the N levels, the subplots. The source of N was urea and the source of organic fertilizer was goat manure. Irrigation was applied through a drip system and N by fertigation. At the end of the third growing season, soil chemical properties were determined and nitrate concentration in the soil solution (extracted by porous cups) was determined. Organic fertilization increased organic matter, pH, EC, P, K, Ca, Mg, Mn, sum of bases, base saturation, and CEC, but decreased exchangeable Cu concentration in the soil by complexation of Cu in the organic matter. Organic fertilization raised the nitrate concentration in the 0.20-0.40 m soil layer, making it leachable. Nitrate concentration in the soil increased as N rates increased, up to more than 300 mg kg-1 in soil and nearly 800 mg L-1 in the soil solution, becoming prone to leaching losses.

Concentrazione di potassio nelle bacche e valori di pH e zuccheri nel mosto della cv Cabernet Sauvignon innestata su diversi portinnesti nel Sud del Brasile.

In field conditions two experiments were carried out in 2000/2001 and 2001/2002, to evaluate potassium (K) content in berries, and pH and total soluble solid values in the must. The experiment 1 was carried on a Udorthent soil and the experiment 2 on a Haplumbrept soil, both at Southern Brazil, Bento Gonçalves city. The Cabernet Sauvignon grapevine was grafted on different rootstocks (Rupestris Du Lot, R. 99, R. 110, SO4, 420 A, 1103, 101-14 and 3309). At full ripening, berries were collected and potassium concentration (2000/2001 and 2001/2002 seasons), pH and total soluble solids (2001/2002 season) were determined. Rootstock didn?t affect potassium content of berries, and pH and total soluble solid values in the must.