Macronutrient Interactions and Microbial Population in Ultisols and Spodosols Affecting the Incidence of Ganoderma Disease

The spread of Ganoderma disease in oil palm plantations is affected by several factors, one of the most significant being the soil type. Different soil types influence the availability of nutrients and moisture, which can affect the growth and spread of Ganoderma. This study investigates the impact of spodosols and ultisols on soil macronutrient dynamics and their effect on microbial populations, ultimately influencing Ganoderma distribution. Using a nested sampling design, we collected data from 120 palms across 411 hectares. We analyzed the impact of soil type (sand, ultisol) on soil pH, organic carbon, macronutrients (P-total, P-Bray, Exchangeable K, Exc-Mg, Exc-Ca), and bacterial and fungal populations at 1 m, 2 m, and 3 m distances from infected and healthy palms. Data analysis employed Two-Way ANOVA. The results reveal that soil pH and organic carbon positively influenced Ganoderma incidence in spodosol soil. At the same time, macronutrients P-total, P-Bray, and K had positive interactions with the disease in both soil types. Conversely, Exc-Mg and Exc-Ca showed positive interactions in spodosol soil but negative interactions in ultisol soil. Nitrogen had no significant impact on spodosol soil. Regarding microbial populations, ultisol soil exhibited higher bacterial populations around infected palms (23.4% at 1 m and 12.5% at 3 m). Spodosol soil showed higher bacterial populations further away (2.3% at 1m and 41.3% at 3 m). Fungal populations were higher in ultisol soil compared to spodosol soil for infected palms (27.01 x 106 cfu/g and 26.00 x 106 cfu/g, respectively). This study highlights the complex interplay between soil type, macronutrients, microbial populations, and the spread of Ganoderma. These findings inform the development of effective disease management strategies for oil palm plantations.