Abstract:
Rubber cultivation in Sri Lanka has been confined in the past mainly to the Wet Zone
where the extent of land under rubber declined rapidly with urbanization. Therefore, to
meet the demand for natural rubber, cultivation has been extended to Uva Province too in
the Intermediate Zone. Ideally, high quality budded plants are required to produce within
the region. However, the time taken for this process is comparatively a little longer than
that in the Wet Zone. The present study was conducted in the government rubber nursery
at Monaragala to examine the effectiveness of different dosages of inorganic fertilizer and
compost on the growth of rubber nursery plants for two months. Fertilizer mixture:
9:11:11:4 for N:P:K:Mg, respectively, recommended by the Rubber Research Institute
was used. Three levels of fertilizer mixture: 1.25 (control), 2.5, and 3.7 g per plant at
fortnight interval were applied. Two levels of compost: 0 and 50 g per plant were used for
the potting mixture with topsoil. Compost and fertilizer levels were considered as two
factors (4 replicates and 25 plants per replicate) and a nursery was arranged as complete
randomized block design. Germinated seeds were transplanted into polybags which were
filled with two potting media. Growth attributes viz. stem height, stem diameter, and
number of leaves were recorded at the 2nd
, 3
rd, 4th, 6th, and 7th weeks; and chlorophyll
content (SPAD), number of leaf whorls at the 7th week after transplanting. Data were
subjected to ANOVA. There was no significant difference (p>0.05) in the growth
attributes as well as in the SPAD value among the treatments tested. Therefore, use of
currently recommended lowest dosage of the fertilizer mixture, i.e. 1.25 g per plant at
fortnight interval without additional compost, when using topsoil is cost-effective in
maintaining the rubber nurseries at pre bud grafting period in the Intermediate Zone of
Uva Province.
Keywords: Compost, Hevea seedlings, Inorganic fertilizer, Intermediate zone
