MSc

The research project entitled “Allelopathic effect of trees grown in homesteads
of Kerala on ginger (Zingiber officinale Roscoe)” was conducted during the period
from February to December 2015. The objective was to investigate the allelopathic
effect of trees commonly planted in the homesteads of southern Kerala on sprouting,
growth and yield of ginger.
The study involved two laboratory bioassays and two pot culture experiments,
all laid out in completely randomized design. The first bioassay comprised eight tree
leaf leachates each at two concentrations and one control totaling 17 treatments each
replicated thrice [jack, mango, tamarind, matty, wild jack, teak, rubber, panal each at
1:10 and 1:15 concentration, and one absolute control (distilled water)]. The second
bioassay was carried out in the same manner with leaf extract. The two pot culture
experiments were laid out in completely randomized design. The first pot culture
experiment was laid out with 17 leaf leachate as treatments, each replicated thrice.
The second pot culture experiment, was carried out to study the effect of different tree
leaf mulches and comprised nine treatments with three replications - M 1 (mulching
with fresh leaf loppings of jack), M 2 (mango), M 3 (tamarind), M 4 (matty), M 5 (wild
jack), M 6 (teak), M 7 (rubber), M 8 (panal), M 9 (control with newspaper). Mulch was
applied as per the KAU recommendations. The ginger variety, ‘Karthika’, was used
for the study.
The first bioassay revealed that the leaf leachates of tamarind (T 3 ) and mango
(T 2 ) severely inhibited the sprouting and the shoot growth of ginger rhizome. All the
leaf leachates reduced the root growth and number of roots significantly and tamarind
(T 3 ) resulted in the highest inhibition. The inhibitory effect was alleviated with
dilution.
In the second bioassay, leaf extracts of tamarind (T 3 ) significantly inhibited
sprouting of ginger. Leaf extracts of mango and tamarind recorded significantly lowershoot growth. Leaf extracts of mango (T 2 ), tamarind (T 3 ) and teak (T 6 ) inhibited the
root growth and number of roots significantly. Leaf extracts of panal (T 8 ) had a
significant stimulatory effect.
In the first pot culture study, plants treated with leaf leachate of tamarind (T 3 )
had least height and number of tillers at 2 months after planting (MAP), while
applying panal (T 8 ) leaf leachate resulted in maximum plant height at 4 and 6 MAP.
The number of leaves was highest in applying panal (T 8 ) leaf leachate, at 6 MAP.
Tamarind (T 3 ) leaf leachate significantly inhibited the root volume and root weight.
Among the physiological parameters, stomatal conductance alone was affected by the
leaf leachate of trees. Application of tamarind (T 3 ) leaf leachate resulted in lesser
yield (443.56 g plant -1 ). However, application of panal (T 8 ), rubber (T 7 ) and matty
(T 4 ) leaf leachates produced significantly higher rhizome yield per plant.
In the second pot culture experiment involving mulching with the tree leaf
loppings, plant height was significantly less in treatments M 2 (mango) and M 3
(tamarind). Rhizome yield was significantly higher when mulched with panal (653.50
g plant -1 ) and was on a par with newspaper (637 g plant -1 ) and rubber (621.40 g plant -
1
) leaves. However, mulching with mango leaves resulted in significantly lesser yield
(512.09 g plant -1 ). Another interesting observation was that in the control where
newspaper were used as mulch, the yield was high (637 g plant -1 ) and comparable to
mulching with panal, rubber, teak, matty, wild jack and jack leaves. Hence ginger is
grown in homesteads and terrace gardens, if available newspaper can be used for
mulching.
Based on the results of the experiments, it can be concluded that leaf leachates
and extracts of tamarind, mango and teak are inhibitory to sprouting and growth of
ginger. Hence, when ginger is planted under the canopy of these trees care should be
taken to alleviate the inhibitory effect. Leaf lopping of tamarind is not ideal formulching in ginger. Leaf loppings of panal, rubber or matty can be recommended for
mulching in ginger.