Effect of long term land use systems on fractions of glomalin and soil organic carbon in the Indo-Gangetic plain

• Long-term cropping disturbance decreases the entire glomalin and SOC fractions.
• Positive correlation appeared among all fractions of glomalin and SOC.
• Higher glomalin C contribution in stable SOC, decreased in disturbed soil.
• Clear variation in other soil properties between disturbed and undisturbed soil.
• Glomalin, SOC and microbial activity chiefly controls soil properties.

Long-term history of tillage and cropping mediated disturbed and undisturbed use soils effect on glomalin related soil protein (GRSP) and soil organic carbon (SOC) and on their sub fractions were investigated in Indo-Gangetic plain region. In this study, shallow soils were collected from 50-year-old monoculture treatments of undisturbed (Dendrocalamus calostachyus, Mangifera indica and Saccharum munja Roxb.) and disturbed (Oryza sativa cultivated field) land use. Our results showed that compared with undisturbed soils, soils under the disturbed use dramatically depleted in SOC, particulate OC (POC), non-particulate OC (NPOC), GRSP, easily extractable GRSP (EE-GRSP) and difficulty extractable GRSP (DE-GRSP). The depletion in labile POC was found to be little higher than physically protected NPOC, and were almost similar among the fractions of GRSP (each decreased by 50%). Further, a linear correlation was found among the fractions of GRSP and SOC, and in turn resulted in the similar relationship with soils bulk density, porosity, pH, available phosphorus, total phosphorus, organic nitrogen's, cations (calcium and potassium), arbuscular mycorrhizal (AM) abundance, and with microbial activity. These results indicate that the factors involve in SOC accumulation simultaneously encourage AM proliferation and in turn GRSP enrichment. Apart from this, the higher contribution of GRSP-C in NPOC (13 to 17%), tended to increase with decreasing soil disturbance, suggesting the role of GRSP in accumulation and stabilization of SOC in this zone. A two component factor structure showed component 1 considerably occupied by fractions of GRSP, SOC and those other variables favouring GRSP and SOC, primarily scored by undisturbed (M. indica and D. calostachyus treatments) soils. The second component which has fewer influence over soil variables, considerably occupied by microbial activity, electrical conductivity, cations and nutrients (available nitrogen, phosphorus) was also exemplified by undisturbed soils (except D. calostachyus treatment). Thus, improving GRSP and SOC stock in disturbed agricultural soil in studied area is of urgent requirement for the long-term goal of C sequestration and sustainable soil health. Our finding should stimulate management plans for degraded lands aimed at recovering the landscape heterogeneity.