Determination of Ideal Snag Length for Rubber Brown-Budded Stumps in Southern Nigeria

Abstract

Rubber plantations are mainly established with the use of rubber budded stumps, which are derived from successfully budded rubber seedling rootstock (stock plant) which have been de-topped; with the ultimate aim of prompting shooting of scion buds which are projected to replace the upper part of the plant hitherto removed during de-topping. The survival, activation and good development of the scion-bud has been reported to be a function of several factors amongst which is the length of the snag; the snag being the protuberant or remnant part of the stock above the stock-scion union; after de-topping Incidentally, the point of cut during de-topping operations is typically left at the discretion of the topper, thereby making the operation subjective and prone to the errors of cutting too near or too far from the bud-scion union and consequently causing undesirable associated outcomes. This study was therefore conducted to determine an ideal snag length; particularly for brown budded rubber seedlings of over 9 months old. As treatments, 22-month-old rubber seedlings were successfully budded and subsequently de-topped at 0, 2, 4, 6, 8, and 10 cm above the stock-scion union and respectively labelled SL-0cm, SL-2cm, SL-4cm, SL-6cm, SL-8cm and SL-10cm to form the six categories of snag lengths put under investigation. The treated planting materials were then lifted/transplanted into the designated experimental plots arranged in a Randomized Complete Block Design (RCBD); with 3 replications. Data on the scion-bud shooting rates, growth parameters (length, diameter, number of leaves, leaf area) of the scion-bud shoots and number of stock-bud shoots were taken at 2 weeks interval until 16 weeks after de-topping (WAD). The shooting rates of scion-buds were significantly higher in the 3 shortest snag lengths i.e. SL-0cm (50.00%), SL-2cm (50.00%), SL-4cm (58.00%) compared to the longer snag-lengths i.e. SL-6cm (25.00%), SL-8cm (25.00%) and SL-10cm (33.25%) at 2 WAD and maintained relative superiority. Nevertheless, only SL-0cm (100.00%) and SL-2cm (83.25%) remained statistically comparable as from 14 WAD. The short snags started off with higher shoot lengths at 4 WAD, but were eventually tallied by shoot lengths in the longer snags. Scion shoot diameter was almost consistently higher in SL-0cm and SL-2cm throughout the sampling duration with SL-0cm, SL-2cm, SL-4cm, SL-6cm, SL-8cm and SL-10cm having 0.96 cm, 0.93 cm, 0.86cm, 0.90 cm, 0.83 cm and 0.83 cm respectively at 16 WAD. The number of leaves did not have a defined pattern while there was no significant difference in leaf area across the different snag lengths. However, the number of stock-bud shoots increased with increasing snag lengths; with SL-0cm and SL-2cm having 0.33/stump and 1.00/stump respectively at both 10 WAD and 12 WAD. Snag lengths 2 cm and 0 cm are recommended (in order of preference) for rubber brown-budded rootstock.