LONG TERM STUDIES TO EVALUATE SOIL FERTILITY FOR CITRUS IN SARPANG, BHUTAN: CURRENT PRACTICES AND NUTRIENT STATUS

Citrus represents Bhutan’s largest fresh fruit export. It is one of the main sources of income for rural households. However, citrus production is declining over the years mostly due to low soil fertility. This paper is the results of the long term studies conducted in 2013 and 2018 to determine the status and development in soil fertility management. Over 200 soil samples were collected from six villages. The soil samples were analyzed and interpreted for pH, organic matter percent (OM%), primary nutrients, carbon to nitrogen ratio (C:N), cation exchange capacity (CEC),and base saturation percent (BS%). The results revealed that soil pH values were within a very acidic range and lower than the optimum pH level of 5.5-6.5. The average OM content was within moderate range and no change was observed over the years in soil fertility rating. The level of phosphorous (P) decreased over the years but no major difference was observed in the fertility rating of total nitrogen percent (N%). Deficiency in potassium (K) was observed, and most of the soils recorded low K levels in both years. The C:N ratio was within moderate to good range, CEC improved over the years but BS% remained to be on the lower side indication acidic soils.