Relationship between variable doses of N, P, K and Ca and the physicochemical and proximal characteristics of andean blackberry (Rubus glaucus Benth.)

Abstract

Literature about the effect of different doses of macronutrients on the quality of Rubus glaucus Benth. berries are still incipient. The aim of this study was to estimate the effect of variable doses of N, P, K and Ca on the physicochemical and proximal characteristics of Andean blackberry fruit. An orthogonal central composite treatment design was carried out in a randomized complete block arrangement, with 25 fertilization treatments and five levels of each nutrient distributed in three blocks. Principal component analysis, multivariate variance analysis and Tukey tests (P < 0.05) were performed to identify significant differences. Low doses of N and high K and Ca allowed to obtain fruit with greater firmness (3.92 ± 0.40 Kgf) in maturity degree 5, while average doses of N, K and Ca, and low P led to higher TSS values (8.10 ± 0.12°Brix). The different fertilization treatments had no significant effect on the chemical parameters of the soil. Crop fertilization with average doses of N, P, K and Ca allowed to obtain fruit with higher firmness values than 5 Kgf in maturity degree 4, low acid value (2.74), a crop yield potential higher than 20 t ha−1 and juice yield of 62.65%, with low fertilization costs. Fertilization plans based on the nutritional requirements of the crop, its phenology and nutritional demand, enables the fruit to grow with differentiated and outstanding physical and chemical characteristics, of interest for different markets.