Molybdenum fractions and soil health under different land uses in acid soils of himachal pradesh

Abstract

Land use exerts a profound influence on soil properties and nutrient dynamics. In contrast to macronutrients, which are well documented, micronutrients like molybdenum (Mo) are under-researched, particularly across land uses. Given crucial role of Mo in plant functions, understanding its availability, cycling and interaction with soil properties, especially in acidic soils, is essential where Mo is generally deficient. Since a considerable portion (17.7 lakh ha) of H.P state consists of acidic soils, the risk of Mo deficiency is high in this region. Therefore, this study entitled Molybdenum fractions and soil health under different land uses in acid soils of Himachal Pradesh was undertaken. Three major land uses: agriculture-based, horticulture-based and natural systems were examined. The agricultural systems included cereal, legume and fodder crops; horticultural systems involved vegetable crops and orchards and natural systems consisted of forests and grasslands. Surface and sub-surface soil samples were collected from these seven land use practices, with three replicates across four locations. The data were analyzed using Randomized Block Design (RBD). Soil parameters varied across locations and land uses and the differences across locations could be attributed to variations in topography, climate, parent material etc. In terms of soil health, natural systems showed better soil properties such as bulk density, porosity, pH, EC, OC, MBC, MBN and SR compared to agriculture and horticulture-based land uses. Conversely, availability of all macro and micro-nutrients except for Mo, was notably higher in cultivated systems (cereal, legume, fodder and vegetable) compared to natural systems. Unlike other nutrients, Mo availability was higher in natural systems (0.143-0.189 mg kg-1 in surface soils) compared to cultivated ones (0.086-0.123 mg kg-1 in surface soils). All Mo fractions, except oxide bound Mo were in higher amounts under natural systems compared to cultivated systems. The per cent contribution of Mo fractions in total Mo followed the trend: exchangeable Mo lt oxide bound Mo lt organically bound Mo lt residual Mo. All Mo fractions exhibited positive and significant relationships with each other, except oxide bound Mo. Available and exchangeable Mo exhibited positive and significant relationship with pH whereas, oxide bound Mo showed negative and significant relationship with pH. The higher availability in natural systems showed that these soils were not inherently deficient in Mo and it is most likely the result of land use practices and intensities of cultivation. Since standard fertilization practices rarely include Mo, cultivated soils can become Mo-deficient over time, this shortfall must be corrected before Mo becomes a major constraint in crop production. newline