Orapin Praprutdee, Jampen Onthong, and Chairat Nilnond

pp. 1003 - 1016

Abstract

The objective of this study was to determine the effect of potash fertilizers on fruit development and fruit quality, nutrient concentration in leaf, peduncle, rind and pulp of longkong fruit and some properties of soil. The experimental design was randomized complete block design (RCB) with 5 replicates (one tree
per replicate) and 6 treatments as follows: (1) without K (control), (2) applied 13-13-21 at 2 kg tree^-1, (3) applied 13-13-21 2 at kg tree^-1 + K₂ SO₄ at 1 kg tree^-1, (4) applied 13-13-21 at 2 kg tree^-1 + KCl at 733 g tree^-1 (5) K₂SO₄
 at 840 g tree^-1 and (6) KCl at 700 g tree^-1. The results showed that K application increased cluster weight, fruit weight, fruit diameter and total soluble solids (TSS), compared with the control (P<0.05), whereas the rind thickness decreased. However, there was no apparent effect on length of peduncle, peduncle weight, number of fruits and juice titratable acidity (TA). Even though K fertilization improved fruit qualities, among the K sources fruit qualities were not significantly different. The fruit qualities of the Kfertilized (average) and control treatments after 14 weeks of fruit set were as follow: cluster weight 473.06 and 336.59 g cluster^-1, fruit weight 432.90 and 272.79 g cluster^-1, fruit diameter 32.75 and 29.96 mm and TSS 17.46 and 14.88 % Brix respectively. Moreover, K concentrations in leaf, rind and pulp in the K-fertilized treatments were higher than in the control (P<0.05), while Ca concentrations in leaf and rind were reversed (P<0.05). However, pulp K concentrations in the K-fertilized and control treatments were not different. Two
application times of K-fertilizer did not give better fruit qualities than a single one, but resulted in higher amount of exchangeable K accumulation in soil. Therefore, it is recommended that KCl can be applied as a single application to longkong trees at 5 weeks after fruit set.