The Effect of Probiotic Fertilizer Concentrations and Pruning on Kristal Guava (Psidium guajava L. cv. Kristal) in the Off-Season Production

Kristal guava is one of the horticultural commodities that is in demand by the public at large amount and can grow well in Indonesia. The low production of Kristal guava in the off-season is one of the causes of not fulfilling the demand for the fruit. The research was conducted in Semanik Village, Badung, Bali, Indonesia from January to July 2023. This study aimed to increase the growth and production of Kristal guava in the off-season through fertilization with probiotic fertilizer and pruning. This experiment used a factorial Randomized Block Design consisting of 2 factors and 3 replications. The first factor was fertilization with probiotic fertilizer consisting of 4 concentration levels, i.e., control (C₀), 10% (C₁), 20% (C₂) and 30% (C₃). While the second factor was pruning, namely: P_t (no pruning) and P_l (pruning 2-3 segments of twig ends + dead twigs + twigs infested with pests). The results showed that the interaction between fertilization with probiotic fertilizer and pruning had no significant effect in off-season production of Kristal guava. The 30% probiotic fertilizer concentration (C₃) was able to increase the growth as indicated by the variable number of new shoots per tree (2.17 shoots) and the number of leaves of new shoots per tree (2.67 leaves) and the off-season production of Kristal guava, reflected in the increase in the number of flowers formed per tree (103.50 flowers), the number of harvested fruits (3.50 fruits) and the weight per fruit (49.72 g) or an increase of 93.46%; 40% and 114.31%, respectively, compared to C₀ which was 53.50 flowers; 2.50 fruits and 23.20 g. The P_l treatment increased the growth as indicated by the variables of leaf chlorophyll content (69.55 SPAD) and leaf relative water content (59.58%) and the off-season production of Kristal guava as reflected by the number of flowers formed per tree (91.25 flowers), the number of fruits formed per tree (8.83 fruits) and the weight of fruit per tree (163.22 g) or an increase of 39.85%; 103.93% and 123.28%, respectively, compared to P_t which was 65.25 flowers; 4.33 fruits and 73.10 g.