Heterogeneity of Soil pH Across Soils Grown for Sugarcane in the Western Viti Levu, Fiji

Soil pH is a key characteristic to be considered in sugarcane agriculture as this form the fundamental basis for the yield output. This study analyzed 772 fallow field soil samples collected from the western division of Fiji Islands sugarcane belt, with samples taken at 0 - 20cm depth using a 1: 5 soil/water ratio for pH determination. Field extension officers from the Fiji Sugar Corporation (FSC) classified the soil types during sampling, with similar soil types subsequently grouped for analysis. The study encompassed 11 distinct soil types, revealed predominantly acidic conditions: 9% strongly acidic, 48% acidic, and 43% slightly acidic. pH values demonstrated considerable variation, ranging from 3.5 to 7.7, with an average of 5.5. Among the 25 sectors studied, Lomawai recorded the lowest pH values while Qeleloa showed the highest, indicating significant spatial heterogeneity in soil acidity across the region. Statistical analysis revealed significant differences in pH levels between soil types (p < 0.001), suggesting that soil type is a crucial factor in determining soil pH characteristics. Nigrescent soil emerged as the predominant soil type across the sugarcane belt, exhibiting moderate pH variability with a standard deviation of 0.59. In contrast, sandy soils were the least common but showed remarkable pH stability with a standard deviation of just 0.21. Clay soils demonstrated the highest pH variability (standard deviation 0.78), suggesting the need for more targeted management approaches in these areas. The findings indicate that soil amendments or crop rotation practices may be necessary to achieve the targeted optimal pH of 6.5 for sugarcane cultivation in these regions. The findings of this comprehensive pH analysis will enable agricultural stakeholders to develop nuanced, soil - type - specific management strategies, ultimately improving soil health, lime amendment efficiency, and crop productivity within Fiji's sugarcane industry.