MSc

The study entitled “Organic preparations and biostimulants for moisture stress
mitigation in container grown okra (Abelmoschus esculentus (L.) Moench)” was
conducted at College of Agriculture, Vellayani, Thiruvananthapuram during 2016 to
2017. The objective of the study was to evaluate the efficacy of organic preparations
and biostimulants on inducing moisture stress tolerance and to assess their impact on
growth, yield and irrigation requirement of okra in urban homesteads.
The field experiment was laid out at the Instructional Farm during July to
October 2016 as Completely Randomised Design with nine treatments replicated
thrice. Uniform sized plastic sacks were selected as containers and they were housed
in a rain shelter. The treatments comprised of application of organic preparations and
biostimulants, which included T1- spraying of fermented cow dung water mixture (10
per cent), T2- spraying of citric acid (0.2 per cent), T3- spraying of sorghum water
extract (5 per cent), T4- spraying of humic acid (1 per cent), T5- spraying of yeast
extract (2 per cent), T6- spraying of moringa leaf extract (3 per cent), T7- spraying of
salicylic acid (100 ppm), T8- spraying of water and T9- no stress treatment (daily
irrigation to field capacity and no spraying). For T1 to T8, irrigation was withheld after
20 days of planting and resumed only when plant showed temporary wilting symptoms.
Spraying as per treatment was given to the plants at 20, 40, 60 and 80 DAP (Days After
Planting).
Results of the study indicated that among the organic preparations and
biostimulants, moringa leaf extract spraying (T6) resulted in significantly higher plant
height (72.33 cm) at 3 MAP (Months After Planting) and root volume (76.53 cm3) at
harvest. With respect to yield attributes, sorghum water extract produced the highest
fruit weight (19.2 g fruit-1) which was on a par with other treatments. Fruit yield plant-
1
was significantly higher (0.25 kg) on spraying citric acid (T2) or humic acid (T4). The
no stress treatment however recorded significantly higher growth attributes, yield
attributes and yield compared to the application of organic preparations and
biostimulants.
Fruit quality aspects like crude fibre and ascorbic acid content were influenced
by the spraying of biostimulants. Significantly higher crude fibre content was recorded
with spraying of sorghum water extract and ascorbic acid content was significantly
higher with yeast extract spraying. Spraying of salicylic acid recorded significantly
higher plant N content while plant K content was the highest in no stress treatment.
Fruit K content was significantly higher with spraying fermented cow dung water
mixture. The highest N uptake was recorded by spraying moringa leaf extract, the
highest P uptake with spraying citric acid, humic acid, moringa leaf extract and
salicylic acid while the highest K uptake was recorded with fermented cow dung water
mixture which was on a par with other treatments. However the no stress treatment
recorded significantly higher N, P and K uptake (2.59, 0.22, 1.55 g plant-1) compared
to biostimulant application.
Irrigation requirement was the lowest with spraying of citric acid (19.04 L plant-
1
) which did not differ from spraying of other biostimulants and was significantly lower
than no stress treatment (22.78 L plant-1). Spraying citric acid or humic acid, cow dung
water mixture or yeast extract produced higher water use efficiency which did not vary
from no stress treatment. Spraying of citric acid also produced significantly higher
water productivity among biostimulants which was on a par with no stress treatment.
The irrigation interval was the highest for citric acid spraying (5.5 days) and lowest for
spraying of water (3.2 days).
Chlorophyll content was the highest with salicylic acid (1.58 mg g-1) spraying
and was on par with citric acid spraying and no stress treatment. Relative Leaf Water
Content (RLWC) one week after 1st spraying was significantly higher with sorghum
water extract and one week after 4th spraying was significantly higher with spraying of
moringa leaf extract or citric acid or no stress treatment compared to yeast extract or
water spraying. The highest organic carbon content of potting mixture after the
experiment was recorded with spraying of humic acid (1.18 per cent) which was
significantly higher than no stress treatment. Among the biostimulants, citric acid
recorded higher net returns (` 3.15 sack-1) and benefit: cost ratio (1.33).
The results of the study indicated that spraying of citric acid (0.2 per cent) to
the container grown okra was found to be the ideal treatment for inducing stress
tolerance, reducing the irrigation requirement and increasing water use efficiency,
water productivity and irrigation interval. It was also found to produce higher yield,
net returns and benefit: cost ratio.