Effect of Nitrogen and Potassium Fertilization on Yield and Fruit Quality in Kiwifruit

摘要

Fertilization is one of the main factors affecting the yield and quality of kiwifruit. Therefore, suitable cultural practices should be studied, including fertilization, in order to guarantee high production levels and the maintenance of the fruit quality. This study lasted for 3 years and experimental data was obtained from a fertilizer trial arranged into completely randomized blocks, with three replications, installed in an orchard located in the Portuguese Region of Bairrada. This experiment was established in order to evaluate the influence of nitrogen and potassium fertilization on the yield and fruit quality of Actinidia deliciosa cv. Hayward. Three levels of nitrogen (30, 60 and 90 kg ha~(-1)N) and four levels of potassium (0, 45, 90 and 135 kg ha~(-1) K_2O) were used, arranged into 12 experimental treatments. Since 2004, nitrogen and potassium were applied annually. The total yield of each plot was evaluated and fruits were graded into six categories according to the weight and deformations: fruits < 65g, [65 -75g], [75 -85g], [85 -105g], ≥105g and deformed fruits. The fruits were sampled to assess some quality parameters namely, firmness of the pulp, titratable acidity, and total soluble solids, at harvest (fruits [85 -105g[size]. The present paper reports the first set of experimental results, corresponding to the experimental period from 2004 to 2006. Results showed a significant mean effect (p≤0.05) of interaction N_xK fertilization on fruit yield. The annual mean application of 60 kg ha-1 N, in addition with the highest rate of potassium (135 kg ha-1 K_2O) led to the highest level of marketable fruit-yield (19.1 tonnes ha~(-1)). The mean effect of nitrogen and potassium fertilization shows a decrease on flesh firmness with both applications.