Tapping panel dryness is an important limiting factor in rubber productivity of Hevea brasiliensis. In order to assess the sensitivity to this syndrome, the effect of two intensive latex harvesting technologies on moderately metabolized GT1 clone, has been studied in the South-Eastern region of Côte d'Ivoire. The rubber trees were planted according to the experimental mono-tree device, "One tree one plot design" a tree constituting a repetition, and 31 trees per treatment, selected on circumference and health status criteria. The parameters measured were rubber production, circumference increase, physiological profile and tapping panel dryness sensitivity. The results showed that induction of tapping panel dryness in latex harvesting system, S/2 d/3 6d/7 ET 10 % Pa 1 (1) 1/ w) was significantly low (0.18 ± 0,22 %) than that of the control (S d/1 6d/7 unstimulated, 1.43 ± 1.45 %). Productivity of this particular system was also good (62 ± 16.32 g.a-1.s-1) and it especially has less stress that can cause physiological fatigue, or even the notch dry. Otherwise, Rubber production, radial vegetative growth, physiological parameters of the latex and the tapping panel dryness rate were influenced by the two treatments applied to GT 1. In addition, the medium and high sucrose contents (16.5 ± 3.01%) and thiol group (0.51 ± 0.13 mmol.l-1) of the latex in the treatment (S/2 d/3 6d/7 ET 10% Pa 1 (1) 1 / w), were instrumental in the response to this stimulation. The sensitivity to the tapping panel dryness is in very close linear relation with the harvest intensity of the latex to which the GT 1 clone has been subjected. These results corroborate and confirm the moderate sensitivity to the tapping panel dryness of GT 1 clone.
La raréfaction du terreau, horizon humifère de surface, qui constitue le substrat de culture pour la production des plants d’hévéa en sac, amène les pépiniéristes d’hévéa à recourir à divers types de fertilisants dont le compost, pour améliorer la croissance des plants. Cependant, très peu d’études ont été consacrées à l’évaluation de l’effet de l’utilisation du compost en pépinière d’hévéa. Cette étude a été initiée en vue d’évaluer les effets de l’utilisation du compost à base de fient de poulet sur la production et la rentabilité de plants d’hévéa en pépinière dans les zones agro-écologiques du sud-est et du centre de la Côte d’Ivoire. Le dispositif expérimental utilisé est un bloc complet randomisé à six milieux de culture (substrats + fertilisants) répétés trois fois. Des données agronomiques et du calcul économique du rendement ont été collectés et analysés. Les résultats obtenus en station et milieu paysan, ont montré que l’utilisation des substrats de culture à base de compost favorise une nette amélioration de la croissance des plants d’hévéa avec de faibles doses de compost comparativement au substrat témoin, non fertilisé. Sur les deux sites d’étude, la production des plants d'hévéa a été optimale et économiquement rentable avec la dose de compost de 300 g/plant, au sud-est et la dose 300 g/plant combinées à l'application fractionnée de 2 ; 3,5 et 5 g d’urée, au centre de la Côte d’Ivoire. Cependant, les doses plus élevées de compost (600 g/plant) ont eu un effet dépressif sur la croissance végétative des plantes d'hévéa, quel que soit le site. Les faibles doses de compost à base de fiente de poulet de 300 g/plant combinées ou non à l'application fractionnée d'urée peuvent donc être, dans les conditions de la présente étude, recommandées pour une production rentable de plants d’hévéa de pépinière en sac. The scarcity of topsoil, the humus-bearing surface horizon that constitutes the substrate for the production of bagged rubber tree nursery, has led rubber nurserymen to resort to various types of fertilizers, including compost, to improve seedling growth. However, very few studies have been conducted to evaluate the effect of compost use in rubber nurseries. This study was initiated to evaluate the effects of using chicken manure-based compost on the production and profitability of rubber seedlings in nurseries in the agro-ecological zones of southeastern and central Côte d'Ivoire. The experimental set-up used is a complete randomized block with 6 growing media (substrates + fertilizers) repeated in 3 times. Agronomic data and economic yield calculations were collected and analyzed. The results, obtained on station and on-farm, showed that the use of compost-based substrates favored a clear improvement in the growth of rubber seedlings with low doses of compost compared to the unfertilized control substrate. At both study sites, rubber plant production was optimal and economically profitable with the 300 g/plant compost dose in the southeast and the 300 g/plant dose combined with the split application of 2, 3.5 and 5 g urea in central Côte d'Ivoire. However, the higher doses of compost (600 g/plant) had a depressive effect on vegetative growth of rubber plants at all sites. The low doses of chicken droppings-based compost of 300 g/plant combined or not with the fractional application of urea can thus be, under the conditions of the present study, recommended for a profitable production of bagged rubber tree nursery plants.
In order to assess the suitability of soils for rubber cultivation in the departments of Man and Toumodi, two new rubber-growing areas, a study was carried out to evaluate the physical, physico-chemical and chemical characteristics of soils under rubber trees (Hevea brasiliensis). The methodology used consisted of a physical description of twelve soil pits, coupled with chemical analyses of the soil samples taken. The pedological profiles carried out revealed that these soils belong mainly to the Ferralsol class with distinctive characteristics, except for those of Kimoukro (Toumodi) which belong to the Cambisol class. The Toumodi soils, of silty-clay-sandy texture, are provided with coarse elements (≥30 p.c) with good internal drainage in the surface horizons. More or less deep, depending on the topographical position, Toumodi soils are slightly acidic (pH = 6) and less supplied with nitrogen and exchangeable bases. The soils of Man, on the other hand, have a sandy-clay texture, with more than 30 p.c. of clay from the surface to the depths. The bulk density (Da = 1.6 ≥ 1.5 g/cm3) was higher for the soils of this locality compared to those of Toumodi (Da = 0.8 ≤ 1 g/cm3). The soils of Man, which are less rich in nitrogen and carbon, are more acidic (pH = 5.4). Exchangeable base contents and CEC are high, mainly in the upper surface horizons.
The quest for greater return on investment at short time is a recurring concern of the rubber industry. Early reverse tapping could be an option to this concern. It is therefore to verify this hypothesis that five different stages of initiation of upward tapping, 6 th , 7 th , 8 th , 9 th year and the control in 10 th year, with application of 2.5 and 5% ethephon was conducted for eight years in the South-East (Bettié) and the Centre-West (Gagnoa) of Côte d'Ivoire. Irrespective of the ethephon concentration used, average yield obtained from upward tapping at 6 th year was 3012 ± 516 kg ha -1 y -1 against 2528 kg ha -1 y -1 in the control, where controlled upward tapping started at 10 th year with a productivity gain of 19%. The mean annual increase in circumference in the upward tapped trees at 6 th year, was 3.02 ± 0.18 cm y -1 and statistically higher than that of the control treatment (2.40 cm y -1 ). Physiological profiles improved during the experiment, regardless of site and of periods of upward tapping. Generally, the sensitivity to panel dryness in the control is more pronounced than that of early upward tapping. Our results suggest very early upward tapping at 6 th year after the 5 years of downward tapping, is the best period to harvest latex from the high tapping panel.
Among the ecological conditions of the environment allowing profitable rubber cultivation, rainfall and the physico-chemical characteristics of the soil are the most important. With this in mind, a study on the adaptability of rubber trees to new agro-morphopedological zones was conducted in the departments of Man and Toumodi. The methodology used to achieve this objective is the realization of pedological pits coupled with physico-chemical laboratory analyses. The open soil profiles reveal that the soils belong mainly to the Ferralsols class with distinctive characteristics, except for those of Kimoukro which belong to the Cambisols class. The Toumodi soils, with a sandy-clay texture (15-35% clay), have a high content of coarse sand (over 40%) and good internal drainage in the surface horizons. They are less dense (≤ 1 g/cm3), with a high coarse element load (40%). These soils are chemically rich with a slightly acidic pH. For the Man soils, the sandy-clay texture, with more than 50% clay, from surface to depth, was the most representative fraction. The coarse element load (≥ 50%) and bulk density (≥ 1.5 g/cm3) were more important. These strongly acidic soils are rich in nitrogen and carbon. Exchangeable bases and CEC are important, mainly, in the upper horizons. In addition, the soil profiles observed in these two departments revealed two major pedogenetic processes: reworking and rejuvenation. At the agronomic level, vegetative growth and rubber production of rubber trees were better in Man than in Toumodi. The physico-chemical characteristics of the soils indicate that the departments of Man and Toumodi are favorable for rubber cultivation, although the soils in Man department are more suitable for cultivation.
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