Cactus Pear Roots Turnover and Total Carbon Sequestration Rate Depends on Soil Volume Availability

Abstract

The influence of soil volume availability on roots carbon turnover and carbon sequestration rate of cactus pear (Opuntia ficus-indica) was studied during three years trial. Since April 2014, 1- year-old cladodes were planted in five different pots size (60, 4, 23, 11 and 7 kg of soil). Due to destructive approach up to nine pots were prepared according to a randomized block design. Three times from April 2014 to June 2016 three pots were destroyed to estimated roots fresh and dry weight. Soil was 1 mm sieved and SOC and δ13C were determined. Considering δ13C of cactus pear (-21) and soil used in the trial (-25.4), root carbon turnover, SOC mean resident time, mineralization rate and total contribution of cactus pear to SOC stock were calculated. A repeated measure ANOVA, on all soil analysis, was performed. Results showed a high significance between pots volume and sampling time. δ13C of soil showed a progressive increase in relation to sampling date and pots size. Pot size, in fact, positively affects roots weight for kg of soil, soil carbon and New Carbon Derived. Mean Resident Time (MRT) of new carbon depended on soil volume, ranging from 8 g of C to 4 g o C for year for larger and smaller pot respectively. In cactus pear (Opuntia ficus-indica) soil volume strongly influenced soil carbon turnover in relation to roots growth and turnover.