Incising to improve penetration and retention of creosote in small-diameter Kenyan-grown Cypress (Cupressus lusitanica)
Turning small-diameter plantation thinnings into value-added products has remained a challenge in many countries, including Kenya. The present study reports on a feasible technique to effectively treat small-diameter cypress for use in ground contact. Samples of pole-size Cypress (Cupressus lusitanica), 106 mm and 138 mm in average diameter, were sampled from thinnings in 7 and 12 year-old plantations, 2.0 m posts removed from butt-ends, debarked, air-dried to 15% moisture content, subjected to four patterns of incising and pressure-treated with creosote (60:40 creosote/furnace oil mix) at a commercial treatment plant. Un-incised controls were prepared and treated in the same fashion. All samples were then conditioned for 48 days under cover, leached in running tap water for 20 days, air-dried to 15% MC and final retentions calculated on a weight-gain basis. Discs were removed from the middle portions of the samples and average radial penetration measured. The results indicated that the closer the incisions (20 mm x 20 mm), the higher the average retentions (86.3 and 80.8 Kg/m3) and penetration (16.8 and 13.9 mm) in 7 and 12 year-old posts respectively, acceptable for ground exposure situations. Un-incised controls recorded lower average retentions (38.9 and 37.4 kg/m3) and penetration (6.8 and 5.8 mm), sub-standard for poles and posts for ground contact usage. Incising as a technique to obtain the required retention and penetration for cypress small-diameter fencing posts and utility poles is viable, and should be refined and investigated further, together with an appropriate treatment schedule. An effective treatment technique is necessary to allow utilisation of a substantial volume of small-diameter cypress removed as thinnings and normally considered as waste in this country.