Root Distribution of Eucalypts Planted on Paddy Bunds in Chachoengsao Province

Abstract

The root distribution of eucalypts planted in Sanam Chai Khet district, Chachoengsao province was investigated at a clonal test site planted on a paddy bund. Eucalypt clones K7, K51, K58 and K59 were planted in a single row with 1 m spacing between trees. Trees sampled were aged 1.5 years and 3.5 years. Three average trees in each age class were selected and soil was removed in a hole 100x50 cm using 10 cm horizons. Soil was excavated until no roots were visible. Soil with fine (diameter < 2 mm) and coarse (diameter > 2 mm) roots in each horizon was collected and washed with water. All fine and coarse roots were oven-dried and weighed to determine the biomass in each horizon. The study on coarse roots used the trench method. Soil was removed until all coarse roots had disappeared. The amount of coarse root was expressed as coarse root per unit area.

The fine root distribution of K58 had the highest biomass located in the layer from 0 to 60 cm, followed by K7, K59 and K51 located in the layer from 0 to 50 cm. The fine root biomass increased with tree age and decreased with soil depth. The coarse root distribution of K58 had the highest biomass, followed by K59, K51 and K7. Coarse root biomass was distributed in the layer from 0 to 60 cm. The coarse root area, located in the soil layer from 0 to 60 cm, for both ages of K51 had the highest cross sectional area, followed by K58, K59 and K7. The coarse root biomass and cross sectional area increased with tree age and soil depth. In addition, K58, K59 and K7 were clones with shallower rooting compared with K51.

Keywords: root system, eucalypts, paddy bund, agroforestry, Chachoengsao province