TANGGAPAN MORFOFISIOLOGI TANAMAN TEBU (Saccharum Officinarum L.) TERHADAP PENURUNAN DOSIS NPK DAN IMPLIKASINYA TERHADAP PRODUKTIVITAS TEBU RATOON

Sugarcane (Saccharum officinarum L.) is a strategic commodity for the sugar industry that
requires balanced fertilization. This study aimed to analyze the morphophysiological respone
of ratoon sugarcane to reduced dosages of compound NPK fertilizer and to determine the
optimal dosage capable of maintaining plant growth and productivity. The research employed
a Randomized Complete Block Design (RCBD) with three replications in Bedilan Village,
Seyegan, Sleman, Yogyakarta. Treatments consisted of five NPK fertilizer dosage levels: P1
(850 kg/ha or standard dosage), P2 (80%), P3 (60%), P4 (40%), and P5 (20%) of the standard
dosage. Data were analyzed using ANOVA at the 5% significance level followed by the Least
Significant Difference (LSD) test at 5%. Parameters evaluated included morphological traits
(stalk height, diameter, plant height, number of leaves, number of internodes), physiological
traits (chlorophyll a, b, and total), stomatal anatomy, soil chemical characteristics, leaf tissue
nutrients, and production parameters (Brix and estimated yield). Reducing the NPK dosage
significantly affected all morphological parameters; the P1 treatment (850 kg/ha) resulted in
the best vegetative growth, though it did not differ significantly from P2 (680 kg/ha). Reducing
the fertilizer dosage below 60% (P4 and P5) significantly suppressed plant height, diameter,
number of leaves, and number of internodes. However, reducing the fertilizer dosage to the
lowest level did not significantly affect leaf chlorophyll content, stomatal characteristics, Brix
values, or total soil N and K content.