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Fertilizer Elements and Gibberellic Acid Interaction on the Buddability of Para Rubber (Hevea brasiliensis Muell. Arg.) Seedlings for Green Budding.
Dissertation Abstract:
Experiments were conducted on Para rubber cultivar Tjir 1 seedling stock for green budding grown on Kabacan loam soil in polyethylene bags for three months to determine the nature of response to gibberelic acid (GA3) on buddability in terms of some growth response parameters, bud take, sprouting capacity and latex flow; and to ascertain the relation of these parameters to the soil and leaf analysis.
Results indicated visible effects of GA3 on the rubber seedlings only at concentrations as high as 20,000 ppm, in terms of terminal node elongation and longer petioles with pale-green and reduced leaf blades.
Nitrogen fertilization markedly increased top root length, N in the soil and leaf, K in the leaf, and soil pH. It also increased the number of cambium layer cells, volume of root system, and sprouting capacity. Effect of the N and GA3 interaction was highly significant in the number of cambium layer cells.
Phosphorus effect was highly significant in the number of cambium layer cells and P in the leaf and significant for P in the soil. Effect of P and GA3 was also significant in total dry-matter yield and volume of the root system.
Potassium effect was highly significant in the number of cambium layer cells and total dry-matter yield and significant for N and K in the soil, K and GA3 interaction effect was significant in bud-take and latex flow, indicating the importance of K in the regeneration of the cambium layer and in osmotic processes for stable latex flow.
Bud take was highly correlated with girth, while sprouting capacity was significantly correlated with bark thickness which, in turn, was closely related to the number of cambium layer cells and K in the leaf.
Findings in this study are still inadequate to conclude unequivocally that N, P and K applied alone or in combination with GA3 can enhance the advancement of buddability stage and increase bud-take and sprouting capacity for green budding of Tjir 1 rubber seedlings. Similar studies are suggested on soils deficient in N, P and K using a higher concentration around 20,000 ppm GA3 for more than a period of three months.