MSc

The present study entitled “Growth responses in Curcuma longa L. to
application of chitin and chitosan” was conducted at the Department of Plantation
Crops and Spices, College of Agriculture, Vellayani, Thiruvananthapuram during
2020-2023 with the objective to evaluate plant growth, yield and curcumin content of
Curcuma longa L. in response to soil application of biopolymers, chitin and its
deacetylated derivative, chitosan.
The planting material of turmeric variety Sona for the study was procured from
College of Agriculture, Vellanikkara. The rhizomes were cut into small bits of 8-10g,
each consisting of two buds and were sown in protrays. After 30 days, the plantlets
were transplanted to growbags. Chitin was applied to potting media and chitosan
solution was applied as soil drenching (SD) at varying concentrations and frequencies
viz., at transplanting (0 MAT) and 60 days after transplanting (2 MAT), to study the
growth responses in C. longa. A foliar spray (FS) with chitosan @ 0.1% at monthly
intervals was given as positive control. The experiment was laid out in Completely
Randomized Design (CRD) with ten treatments and three replications. The treatment
consisted of chitin 10 g per plant applied at 0 MAT (T1), chitin 10 g per plant applied
at 0 MAT and 2 MAT (T2), chitin 15 g per plant applied at 0 MAT (T3), chitin 15 g
per plant applied at 0 MAT and 2 MAT (T4), chitosan 0.2 % SD at 0 MAT (T5),
chitosan 0.2 % SD at 0 MAT and 2 MAT (T6), chitosan 0.6 % SD at 0 MAT (T7),
chitosan 0.6 % SD at 0 MAT and 2 MAT (T8), chitosan 0.10% FS at monthly
intervals (T9) and absolute control without chitin or chitosan (T10).
The observations on plant growth parameters viz., plant height, number of
leaves, number of tillers and leaf area were recorded at monthly intervals from 0 to 6
MAT. These parameters showed significant variation among the treatments. At 6
MAT, T9 recorded maximum plant height (116.76 cm) which was observed to be on
par with T3. The number of leaves (24.95) and leaf area (896.27 cm
2
) were also
observed to be maximum in T9 which was on par with T3 and T4. T9 reported
maximum number of tillers (6.83) also.
The data on rhizome and root parameters were recorded at harvest. The rhizome
spread (25.48 cm) and thickness (3.79 cm) were found to be maximum in T9 and was
on par with T2, T3 and T4. The application of chitin and chitosan did not influence root
length and root spread of turmeric rhizome. The root weight was found highest in T9
(fresh - 29.58 g plant-1
and dry – 13.66 g plant-1
), which was on par with T1, T2, T3 and
T4.
The effect of chitin and chitosan application on chlorophyll content and defense
enzymes (peroxidase and polyphenol oxidase) were recorded at 4 and 6 MAT. T9
exhibited higher leaf chlorophyll, peroxidase and polyphenol oxidase content at both
the stages. The quality parameters viz., carbohydrate, volatile oil, oleoresin, curcumin
content of turmeric rhizome were found to be significantly influenced by the
application of chitin and chitosan. The carbohydrate content was also observed to be
higher in T9 (14.49 mg g-1
) and was on par with T3 and T4. T9 reported the highest
volatile oil (5.13 %), oleoresin (13.30 %) and curcumin (8.06 %) content, which was
found to be on par with T1, T2, T3 and T4.
The population of beneficial microorganisms present in the plant root zone was
significantly influenced by the application of chitin and chitosan. T4 recorded the
highest nitrogen fixing bacterial count (72.20 x 103
cfu g-1
soil). The largest population
of phosphate solubilizers (7.10 x 103
cfu g-1
soil) was also recorded in T4, which was on
par with T3 and T8.
The chitin and chitosan treatments significantly influenced the yield parameters
of turmeric. The number, length, girth and weight of mother, primary and secondary
rhizomes were found to be highest in T9. The number of fingers were found to be the
highest in T3 (32.27) which was on par with T9 (31.40). T9 recorded significantly
higher fresh (504.93 g plant-1
) and dry (137.23 g plant-1
) rhizome yield.
Total dry matter content (191.27 g plant-1
) was found to be the highest in T9.
This value was on par with T3. The uptake of N and P was found to be significantly
higher in T3 and T9. There was no significant variation among the treatments in the
uptake of K. The harvest index of turmeric plants showed significant variation among
the treatments. The harvest index was reported to be the highest in T9. Among the
various treatments tried, significantly higher benefit cost ratio (1.88) was observed
with T9.
In the study, among the treatments involving foliar and soil application of chitin
and chitosan, the foliar spray of 0.1% chitosan at monthly intervals exhibited the best
results in terms of growth, metabolite production, yield and benefit cost ratio. On
comparing the soil application of chitin and chitosan, chitin 15 g per plant applied at
transplanting showed better performance with respect to growth, metabolite
production and yield. This treatment (T3), though followed chitosan foliar spray with
respect to yield, was observed to be on par with respect to quality parameters. All the
treatments involving chitin application gave better performance in terms of yield and
quality (volatile oil, oleoresin and curcumin content) over the control and in
comparison to the soil application of chitosan. Based on the observations of the
present research programme, further field study has to be envisaged to confirm the
effect of soil application of chitin and chitosan.