Assessment of Soil Nutrients Status of Mandarin Orchards in Dagana

Authors: Kinley Tshering, Yeshi Zangpo, Pema Chofil, Tashi Phuntsho  & Ugyen Dorji

ABSTRACT

Mandarin is an important fruit crop for Bhutan’s economy. In 2017, 38.28% of income earned from the sale of fruits was from mandarin. Mandarin is cultivated in 17 districts of Bhutan. Dagana district in west central Bhutan is an important mandarin growing district. The productivity of mandarin trees in Dagana is low as compared to other districts. In 2017, a mandarin tree which has at least attained three years of age and started bearing fruits of economic value on an average yielded 39 kg of fruits in Dagana, whereas a mandarin tree in Trashigang on an average yielded 81 kg of fruits.There is a scope of improving productivity of mandarin trees in Dagana. One way to improve productivity of the plant is through balanced manuring and fertilization at right time as plant productivity is directly linked with soil fertility level in the orchard. Mandarin performs best in sandy loam soils with pH ranging from 5.5 to 6.5. Generally, soils with low nutrient content will have high response to fertilizer application than soil with high nutrient content. In order to study the soil fertility level in mandarin orchards of Dagana, five important mandarins growing gewogs in the district namely Drugyegang, Trashiding, Tsendagang, Goshi and Kana were selected. Soil sampling was done in those pilot gewogs to study the status of important soil parameters in orchard. Eighty composite soil samples consisting forty top soils and forty subsoil were collected from five pilot gewogs. From each gewog, sixteen composite samples were collected consisting of eight topsoil and eight subsoil from eight different mandarin orchards. Top and subsoil samples were collected from 0-20 cm and 20-40 cm depth respectively. Samples were analyzed and soil fertility level among five gewogs was compared followed which fertilizer recommendations were drawn. Analysis results showed that in general, the soil pH was moderate to slightly acidic, percent carbon at medium level, nitrogen at low level, available phosphorus at high level, available potassium at medium level and cation exchange capacity at low level. The most common soil texture was sandy loam. It could be concluded that the improvement in the level of percent carbon, nitrogen and potassium in soil could improve the productivity of mandarin in Dagana.

Keywords: Percent carbon, Nitrogen, Available potassium, Soil texture, Cation exchange capacity

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