Foliar fertilization with potassium, calcium and boron. Incidence on nutrition and quality of fruits in ‘Nova’ mandarin

Abstract

The splitting or “cracked fruit” is a factor that determines the production of mandarin ‘Nova’ in the Northeastern Argentina. The objective was to evaluate the incidence of foliar fertilization with potassium, calcium and boron on splitting, nutrition, productivity and fruit quality.Six treatments T1: control, T2: Ca (NO3)2 at 2 %, T3: 0,2 % Ca-B, T4: Ca-B at 0,4 %, T5: Ca-B at 0,6 %, T6: 4 % KNO3, applied at three times, except the control, in a randomized complete block design with four replicates and four plants per replicate. Leaf samples were taken in March, September and December for each treatment in three consecutive seasons, with concentrations of nitrogen, phosphorus, boron, potassium, calcium, magnesium, zinc, iron, copper and manganese being determined. Before harvest, 20 fruits were sampled per experimental plot, and the following variables were evaluated: bark thickness (mm), equatorial diameter (mm), fresh mass (g), juice content, juice percentage, total soluble solids (°Brix), total acidity (expressed as % citric acid) and maturity index (MI). The addition of Ca and K was associated with increases of these nutrients in plant shell thickness, size, weight and fruit juice, as well as with the least amount of windfalls by splitting or cracked: the contribution of Ca and B to fruit quality variables related. Provide Ca, K and to a lesser extent, decreases the incidence of splitting or cracking in mandarin ‘Nova’.