Effect of oil cake application on soil and leaf nutrition and on fruit yields in non-astringent persimmon (Diospyros × kaki thunb.) trees

Abstract

Various amounts of pelletised oil cake were applied to mature, non-astringent ‘Fuyu’ persimmon (Diospyros × kaki Thunb.) trees from 2011 to 2013, to evaluate the most appropriate rate of application of the organic fertiliser to improve tree vigour and reproductive growth. Treatments included application of 0, 25, 50, 75, or 100% of the recommended amount (RA) of oil cake, respectively. Oil cake application at 50%, 75%, or 100% of the RA increased dry matter (DM) production by >1,500 kg ha⁻¹ compared to the 0% RA control. All rates of application of oil cake increased the pH, organic matter content, macro-nutrient concentrations, cation exchange capacity, and electrical conductivity of the soil at depths of 0 – 20 cm in 2012 and in 2013. Consequently, all applications of oil cake increased leaf N concentrations by >1%, and resulted in more than four water sprouts (shoots) per tree compared to the 0% RA treatment in 2012 and in 2013. Light interception by the central region of the canopy of each tree was reduced as rates of application of oil cake increased (R² = 0.559). All rates of application of oil cake increased mean fruit weights by >8 g, and fruit firmness values by >1.4 N, compared to the 0% RA controls. The 3-year average fruit yield was highest (29,110 kg ha⁻¹) in the 50% RA treatment. Gross incomes from the 50% RA treatment in 2012 and in 2013 were approx. 19% higher than those from the 0% RA controls.Together, these results indicate that 50% RA was the optimum rate of application of oil cake to increase fruit yields, nutrient levels, and the profitability of non-astringent persimmon trees.