MSc

Stevia rebaudiana is an alternative sugar crop that is becoming popular
in various parts of the world. It belongs to the sunflower family, Asteraceae,
and is native to Paraguay (South America); hence called Paraguay’s sweet
herb. Being a natural sweetener it is also known as sweet leaf, honey yerba,
honey leaf, meeti tulsi, sweet chrysanthemum, and candy leaf. The plant
contains steviol glycosides (SVglys), which has importance in the human diet
as a low-calorie and high-potency sweetener. In addition to sweetening
properties, Stevia rebaudiana also has anti-hyperglycemic, anti-cancer,
hepatoprotective, anti-hypertensive, anti-caries, antioxidant, and anti-bacterial
properties. Since the fresh herbage is the main economic part of stevia,
production of more leaf biomass with higher steviol glycosides is the main
criterion for crop performance.
The present study entitled “Agronomic management for enhancing
yield and quality of stevia (Stevia rebaudiana Bertoni)” was conducted at the
Department of Agronomy, College of Agriculture, Vellanikkara, Thrissur
during September 2021 to May 2022. The objective of the study was to
standardize proper spacing and pinching time for stevia. A field experiment
was conducted in Factorial Randomized Block Design (FRBD) with three
replications. The treatments consisted of three spacing levels viz., 15 cm × 10
cm, 20 cm × 10 cm, and 15 cm × 15 cm, and four pinching intervals viz.,
pinching at 20 days after planting (DAP), pinching at 30 DAP, pinching at
flower bud initiation and no pinching (control).
Both spacing and pinching significantly influenced growth parameters
such as plant height, number of branches and leaves, fresh and dry leaf yield,
per plant herbage yield, and total herbage yield. Taller plants were seen with
closer spacing (15 cm × 15 cm) throughout the crop growth period. Though
the growth parameters were higher at a spacing of 15 cm × 10 cm at early
growth stages of stevia (20 DAP), in subsequent stages, these were higher in
wider spacing of 15 cm × 15 cm. Closer spacing resulted in the highest total
herbage yield at harvest (10925 kg ha-1).
Pinching is an important agronomic technique that helps to enhance
vegetative growth. In general, yield related characteristics like the number of
branches and leaves were found to be higher in pinched plants than in nonpinched plants. Plant height was significantly lower in the pinched plants
compared to the unpinched plants. Plant height reduced drastically when
pinching was performed during their early vegetative growth. At the flower
bud initiation stage, a minimum plant height was seen in the plants where
pinching was carried out at 20 DAP compared to pinching done at 30 DAP.
One month after planting, 20 DAP-pinched plants had more branches and
leaves, while at the beginning of the flower bud, 30 DAP-pinched plants had
more. At the time of harvest, plants pinched at the beginning of the floral bud
initiation produced the highest overall herbage yield, followed by plants that
had received pinching at 30 DAP, no pinching, and pinching at 20 DAP,
respectively.
The interaction between spacing and pinching was also significant with
respect to total herbage yield. Planting stevia at a spacing of 15 cm × 10 cm
with pinching at the initiation of floral buds proved to be the best treatment
concerning total herbage yield at harvest. Total glycoside content was
unaffected by different plant spacings and pinching. However, significant
variation was observed for total glycoside yield (kg ha-1) concerning spacing
and pinching. It was higher in the stevia planted at a closer spacing of 15 cm
× 10 cm, and received pinching at flower bud initiation
The study suggests growing stevia at a closer spacing (15 cm × 10 cm)
and pinching at the flower bud initiation stage for higher herbage and glycoside
yield under Kerala conditions.