Phosphorus influence on quality and yield of tubers of dual purpose potato cultivars

ABSTRACT

Even in areas with high levels of phosphorus (P) available in the soil, application of this nutrient is common, aiming to increase potato tuber yield and size. However, the effect of high P rates on tuber yield and quality is not known in these cases. The objective of this study was to evaluate the influence of P fertilization on yield and characteristics of tuber quality of dual purpose potato cultivars, grown in soils with low (14 mg/dm³⁾, medium (36 mg/dm³⁾ and high (70 mg/dm³⁾ P availability. In the three soils, we used the randomized blocks design in a 2x5 factorial scheme, with four replications. The treatments consisted of two potato cultivars (Asterix and Markies) and five P₂O₅ rates (0, 125, 250, 500, and 1,000 kg/ha). The cultivar Markies was less productive than Asterix but had tubers with higher quality characteristics, such as firmness, soluble solids, titratable acidity, pulp pH and protein concentration. In soils with low, medium and high P availability, the marketable tuber yield of both cultivars was increased by 376%, 41%, and 26%, respectively, up to maximum agronomic rates of 500, 255, and 239 kg/ha P₂O₅. Under low P availability, fertilization increased the average weight, firmness, pulp pH and starch concentration, and decreased the reducing sugar concentration in tubers. In soils with higher P availability, besides having exercised less influence on the yield and quality of tubers, the phosphate fertilizer increased levels of reducing sugars in tubers up to the rate of 453 kg/ha P₂O₅, which is not interesting for the industrial processing of potatoes.

Keywords:
Solanum tuberosum; marketable yield; reducing sugars; starch; nutrient availability.