PROCEEDING ICTESS (Internasional Conference on Technology, Education and Social Sciences)
Vol 8 (2026): ICTESS 8th

Study on the Application of Seaweed Extract and NPK Fertilizer on the Growth of Black Potato (Plectranthus rotundifolius)

Okky Chandra Kumara (Universitas Slamet Riyadi Surakarta)
Dewi Ratna Nurhayati (Universitas Slamet Riyadi Surakarta)
Avisema Sigit Saputro (Universitas Slamet Riyadi Surakarta)



Article Info

Publish Date
04 Oct 2026

Abstract

Black potato (Plectranthus rotundifolius) is a potential alternative food crop to substitute rice. However, its low productivity in Indonesia currently averaging around 15 tons/ha is influenced by factors such as sub-optimal nutrient supply and limited availability of high-quality planting materials. This study aims to examine the effect of applying seaweed extract as a biostimulant along with NPK fertilizer (16-16-16) on the growth and yield of black potato. The research was conducted at the Experimental Farm of the Faculty of Agriculture, UNISRI, Surakarta (130 m a.s.l.). A 4 x 4 factorial Completely Randomized Design (CRD) with three replications (totaling 48 experimental units) was employed. The first factor was the dosage of seaweed extract (0, 1, 2, and 3 mL/L), and the second factor was the NPK dosage (0, 200, 400, and 600 kg/ha). Data were analyzed using Analysis of Variance (ANOVA) followed by Honestly Significant Difference (HSD) test at the 5% significance level. The results showed a significant interaction between seaweed extract and NPK fertilizer on plant height, with the best combination observed at 3 mL/L seaweed extract and 600 kg/ha NPK (34.6 cm). Meanwhile, no interaction was found for the number of branches; however, each single factor had a significant effect. The single treatment of 3 mL/L seaweed extract produced the highest number of branches (15.5 branches), while 600 kg/ha NPK alone yielded 15.1 branches.

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