Micro-nutrient pools and their mobility in relation to land-use system in a cold high altitude Himalayan mountainous region

Abstract

Land-use change significantly impacts soil micro-nutrients distribution and transformations due to their inefficient scale- and location-specific management in different ecosystems. We studied the changes in micro-nutrients (viz. Zn, Cu, Fe and Mn) availability and their transformations in soils of hilly landscapes under five distinct land-use systems including mono cropping, double cropping, agroforestry, orchards and the vegetable crops to explore relationship between different fractions of variable solubility and their mobility in response to land-use change. Among the compared land-use systems, DTPA-Zn, Fe, Mn and Cu comprised ~ 3.0 to 8.2%, ~ 0.21 to 0.35%, ~ 1.2 to 6.3% and ~ 7.6 to 17.5% of their respective total content in soils. The agroforestry system had significantly (p < 0.05) higher DTPA-Zn and Mn, compared with mono-and double cropping system. However, the orchard soils had ~ 2.1, 2.0 and 3.4-times higher DTPA-Zn, Fe and Cu concentration than the agroforestry system. The agroforestry system was distinct with significantly highest proportion of total Cu retrieved as amorphous oxide bound (~ 20.5%), crystalline oxide bound (~ 33.6%), organic matter bound (~ 2.1%), while the lowest proportion was accumulated as residual form (~ 43.8%), compared with the other studied land-use systems. The mobility factor that explicit micro-nutrient transformations among soluble and stable pool revealed that monocropping had the significantly lowest (~ 3.3%), while the agroforestry system had the highest Zn mobility factor (~ 4.9%). On the other hand, agroforestry system had significantly lowest (~ 1.8%), while the soils under vegetable crops had the highest Mn mobility factor (~ 7.5%). The principle component analysis (PCA) elucidated residual micro-nutrient (Zn, Fe and Mn) fraction as significant contributors to discern land-use change in fragile hilly landscapes. These results highlight the importance of micro-nutrients management through robust interventions for long-term sustainability different land-use systems in a cold high altitude Himalayan mountainous region.