Pattern of Root Distribution in 30-month Old Five Tree and Two Shrub Species of an Arid Region of North-western India

Structure and distribution of root systems were studied in 30-month old five tree species. Acasia nilotica, Leucaena leucocephala, Dalbergia sissoo, Azadirachta indica and Prosopis cinerario and two shrub species, P. juliflora and Cajanus cajan raised at a spacing of 4 × 0.5 m in an arid region of North-western India. Maximum penetration of root systems was observed in P. cineraria (138 cm of soil depth), followed by A. nilotica, D. sisoo, L. leucocephala and P. juliflora , whereas A indica (85 cm) and C. cajan (65cm) showed comparatively a shallow root systems. P.juliflora showed a maximum root spread (347 cm), followed by L. leucena (228 cm), A. nilotica (216 cm), D. sissoo (187 cm), A. indica (95 cm), C. cajan (80 cm) and P. cineraria (31 cm). Top 30 cm of soil depth had the maximum distribution of root biomass in C. cajan. A. indica and L. leucaena (45-62% of the total), whereas the 30-60 cm soil horizon had the maximum distribution of root biomass in P.juliflora. A. nilotica and D. sissoo (34-40% of the tota1), Root distribution in P. cineraria was almost uniform throughout the soil column. Surficial location of a high proportion of roots in the stands of C. cajan, A. indica and L. leucaena indicates that these species will show strong root competition if intercropped with crops as compared to A. nilotiea, D. sissoo and P. Juliflora which had subsurface location of most of the roots. A vertical root system and narrow crown in P. cineraria , make the species most suitable for agroforestry system.