Fertility status of mulberry (Morus indica L.) growing soils of upper Brahmaputra valley region of north eastern India

Abstract

Mulberry (Morus indica L.) is an agroforestry species grown extensively in India as multipurpose tree. In north eastern India, it is cultivated as sole crop for rearing silkworm under low management practices without any chemical fertilizers and organic inputs. Besides, limited scope of incorporation of mulberry leaves in soil prevents the addition of organic matter into soil. Therefore, the quality of mulberry leaf as well as silk solely depends on the nutritional status of soil on which mulberry is grown. In the present investigation, an attempt was made to assess the fertility status of soil under mulberry cultivation as sole crop in six rural development blocks namely, Kakodonga, Dergaon, Kathalguri, Podumoni, Sarupathar and Bokakhat of Golaghat district in upper Brahmaputra valley of Assam in north eastern India. Results indicated that soils were extremely to strongly acidic (pH < 5.5) in 44% of the mulberry gardens. Organic carbon content was medium to high in 80% of the surface soil samples (0-20 cm.) and low to medium in 84% of sub-surface soil samples (20-50 cm.). About 51% of the sub-surface soil samples were low in N and 98% of the sub-surface soil samples were low in P status. Among micronutrients, B was deficient in more than 80% samples; whereas, Zn deficiency was found in 36% of the sub-surface samples. Nutrient index values indicated that mulberry growing soils of Kakodonga and Bokakhat were the least fertile as far as the availability of major nutrients are concerned due to the soil resources of recent origin (Entisols) with coarse texture occurring on active flood plains in these blocks. The study indicated the wide spread nutritional deficiency in soils of upper Brahmaputra valley of north eastern India.