Adubação potássica na produtividade e qualidade do morangueiro cv. Camarosa

Abstract

Nutrition and fertilization influence on physical and chemical characteristics of strawberry and potassium is a nutrient that improves the quality of strawberry. The aim of this study was to evaluate the influence of sources and rates of potassium fertilizers on agronomic and postharvest characteristics of strawberry fruit (Fragaria x ananassa Duch.) cultivar Camarosa. The experiment was carry out in pots under greenhouse, in Guarapuava, PR, in a distrophic brown Oxisol. The design was completly randomized, with four replications, in a factorial arranged 6x3 (six rates of potassium x three sources of potassium fertlizers). For post-harvest characteristics, fruit potassium content and fruit potassium recruitment the design was completly randomized in a split plot, with three replications, where the main plot consisted of the factorial scheme 6x3 (six rates of potassium x three sources of potassium fertlizers) and the subplot consisted of four time of harvest. The sources used were potassium sulphate, potassium nitrate and potassium chloride in rates: 0, 200, 400, 600, 800 e 1000 kg ha?¹ de K2O. The evaluated characteristics were leaf potassium content, fruit potassium content, yield per plant, fruit number per plant, average fruit weight, moisture, soluble solids, titratable acidity, soluble solids and titratable acidity ratio, pH, reducing sugars, phenolic compounds, anthocyanins and ascorbic acid, as well as the correlation between these characteristics and potassium recruitment by fruit. The increase in potassium rates led higher levels of potassium in fruits and leaves, the largest leaf potassium content provided by KNO3 and the highest fruit potassium content by KCl and K2SO4. The yield and fruit number per plant were increased by increased potassium rates and the highest average fruit weight was estimated in the rate of 594 kg ha?¹. Potassium improved some quality attributes and bioactive compounds in strawberry fruits, because it increased the soluble solids, reducing sugars, phenolic compounds, anthocyanins and ascorbic acid up to a certain rate, and decreased the fruit moisture content. However higher potassium rates tended to increase titratable acidity and decrease the pH. For increasing the agronomic characteristics, the source would be most suitable is KNO3, for best quality attributes is KCl and for larger bioactive compounds content is K2SO4. For these three potassium fertilizer, the K2O rate that provide satisfactory production combined the best fruit quality is between 500 and 700 kg ha?¹.