The availability of nutrients in the soil is crucial for the growth and yield of potato plants. However, Andisol soil, which dominates the Karo Regency, is characterized by low nutrient availability and high phosphate retention, resulting in nutrient stress for plants. This study was conducted in Karo Regency at various elevations and slope gradients based on Land Unit Map. Soil analysis was carried out at the PT Socfindo Soil Laboratory, and microbial analysis was conducted at the Soil Biology Laboratory, Faculty of Agriculture, and Microbiology Laboratory, University of North Sumatra. Soil sampling used observational method on potato cultivation areas from February 2023 to February 2024. Observed cropping systems included: monoculture, monoculture with mulch, intercropping, and crop rotation. The research employed a descriptive-analytical method and data were analyzed using one-way ANOVA followed by a DMRT test at a 5% significance level. The results showed that crop rotation systems significantly improved soil physical and chemical properties, microbial populations, and potato yields, especially in Land Unit Map 1. At elevations above 1300 meters with 84.03% soil moisture and 82.77% air humidity, the highest potato yield reached 24.67 tons/ha, with nitrogen-fixing microbe populations at 51.67 cells/gram.
Napitupulu et al. (Fri,) studied this question.