Root recovery of five tropical tree and shrub species by sieves of different mesh sizes

Accurate quantitative assessment of roots is key to understanding the belowground plant productivity as well as providing an insight of the plant-soil interactions. In this study, root recoveries by sieves of different mesh sizes (2.0, 1.0, 0.5 and 0.25 mm) were measured for five tropical tree and shrub species grown in monoculture stands: crotalaria (Crotalaria grahamiana Wight and Arn.), pigeonpea [Cajanus cajan (L.) Millsp.], sesbania [Sesbania sesban (L.) Merr.], tephrosia (Tephrosia vogelii Hook F.), siratro [Macroptilium atropurpureum (DC.) Urb.] and tithonia [Tithonia diversifolia (Hemsl.) Gray]. Root samples were take from 0-15 cm soil depth. Recovery of coarser roots (> 1.0 mm) ranged from 70 to 93% and 90 to 98% of the cumulative root length and biomass respectively. The proportion of root length of the finer roots (< 1.0 mm) was greater for pigeonpea (30%), tithonia (22%) and siratro (18%) compared with other species, but contributed negligibly to the cumulative total root biomass for all species. The use of 0.5 mm sieve improved the recovery of root length for most species but had little effect on root biomass. The 0.25 mm sieve was most effective in capturing finer roots (< 0.5 mm) of pigeonpea which represented 16% of cumulative root length and 4% of root biomass recorded for this species. Recovery of roots of different diameter classes depended on species, suggesting that for an improved estimation of root parameters especially when sieves of large mesh sizes (> 0.25 mm) are used, a correction factor could be useful for root length measurements but not root biomass measurements for a particular species in each site and for a specific study.