Unveiling the intriguing array of soil acidity variations within sixteen captivating tea estates spread across Northeast India

In the lush tea estates of Northeast India, the growth of the tea plant (Camellia sinensis L.) hinges on the intricate dance of soil properties. This present study delves into the soil characteristics of sixteen tea estates, situated spanning the verdant landscapes of Assam and the enchanting Darjeeling hills in West Bengal. We meticulously analyzed soil pH, organic carbon (OC) content, texture, available nitrogen, phosphorus, potassium, sulfur, exchangeable calcium, and magnesium using rigorous standard methods. In our analysis, we also investigated various forms of soil acidity. These include exchangeable acidity (EA), exchangeable aluminum (EAl), exchangeable hydrogen (EH), extractable acidity (ExtA), hydrolytic acidity (HA), non-exchangeable aluminum (NEA), pH-dependent acidity (pHDA), total acidity (TA), and total potential acidity (TPA). The findings revealed that most of the estates have soil with acidity levels below 4.50 rendering it unsuitable for tea cultivation. The various acidity fractions exhibited specific ranges for different soil components, with pH-dependent acidity emerging as the primary contributor to TPA, and EAl, exerting the most significant influence on TA in the soils being investigated. The study also demonstrated a strong inverse relationship between pH and all forms of acidity, except for non-exchangeable acidity and hydrolytic acidity. Furthermore, the presence of OC was found to have a substantial impact on soil acidity, displaying a notably strong positive association with EA, pHDA, and TPA. Canonical correlation analysis (CCA) revealed the relationship between soil acidity and its physical and chemical properties. The principal component analysis (PCA) showed that the first six PCs accounted for over 80% of the variability, with PC-1, PC-2, and PC-3 describing 31.86, 20.78, and 14.13% respectively. These results highlight the urgent need for soil amendments and better field management practices to combat soil acidity for sustainable tea cultivation.