Impact of chronosequence of poplar based agroforestry system on storage of soil organic carbon in active and recalcitrant pools

Abstract

The study comprised of five land uses viz., sites having continuous poplar (Populus deltoides)-basedagroforestry system (AFS) for 10, 20 and 30 years, fodder [pearlmillet (Pennisetum glaucum)/ sorghum(Sorghum bicolor)]-fodder [oats (Avena sativa)/ berseem (Trifolium alexandrinum)] (F-F) rotation and fallowland (control) to determine depthwise (0-15, 15-30, 30-60 and 60-90 cm) changes in total C (TC), soil inorganic C (SIC), soil organic C (SOC), total organic C (TOC) and its fractions in different land uses. The TOC poolsconsisting of very labile C (VLC), labile C (LC), less labile C (LLC) and recalcitrant C (RC) were determined. Fallow land had highest (1.53 Mg m ) whereas 30 years AFS had lowest bulk density (1.42 Mg m ) of the -3 -3surface soil depth. The TC, SOC and TOC stocks followed the order: AFS > F-F > FL in various soil depths. Theactive carbon (AC) pools (VLC + LC) were higher in 10-year plantation cycle (62.3% of TOC) than 30-yearcycle (32.9% of TOC), whereas the passive carbon (PC) pools (LLC + RC) were higher in 30-year plantationcycle (67.1%) than in 10 years (37.7%) in surface depth. The contribution of LLC to PC was higher in 30-yearplantation cycle (65%) than in 10-year plantation cycle (48%). Therefore, long-term adoption of poplar basedagroforestry system plays a significant role in sequestration of resistant carbon pools in the soils.