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OPTIMIZATION OF LETTUCE GROWTH THROUGH SUBSTRATE AND
NUTRIENT COMBINATIONS IN HYDROPONICS
Kuchkorova Gulasal
Tashkent Institute of Irrigation and Agricultural Mechanization Engineers
(TIIAME)-National Research University
https://doi.org/10.5281/zenodo.15285771
Abstract:
This study investigates the effects of different growing substrates and nutrient
treatments on the vegetative growth and average leaf weight of
Lactuca sativa
(lettuce)
cultivated in a hydroponic system. Four substrates—vermiculite, perlite, coconut coir, and
rockwool—were evaluated in combination with three nutrient regimes: mineral salts alone,
mineral salts with humic acid, and mineral salts with microalgae. The results reveal that the
inclusion of humic acid and microalgae significantly enhanced plant performance, with the
highest average leaf weight observed in the rockwool + mineral salts + microalgae treatment
(31.233 g). Rockwool outperformed other substrates due to its superior water retention and
aeration properties. Microalgae supplementation contributed the most notable improvement,
likely due to its bioactive compounds and nutrient-enhancing effects. These findings
emphasize the importance of optimizing both substrate and nutrient combinations to improve
lettuce yield in soilless cultivation systems.
Annotation
This study explores the impact of different hydroponic substrates and nutrient
formulations on the average fresh leaf weight of
Lactuca sativa
(lettuce). Four types of
growing media—vermiculite, perlite, coconut coir, and rockwool—were tested in
combination with three nutrient treatments: mineral salts, mineral salts with humic acid, and
mineral salts with microalgae. The results showed that both humic acid and microalgae
significantly improved plant growth, with the rockwool and microalgae combination yielding
the highest average leaf weight (31.233 g). These findings suggest that integrating organic
supplements with suitable substrates can significantly enhance lettuce production in soilless
systems.
Keywords
Hydroponics,
Lactuca sativa
, Rockwool, Microalgae, Humic acid, Substrate selection,
Soilless cultivation, Leaf weight, Biofertilizer, Nutrient solution.
Introduction
Hydroponic systems have emerged as efficient alternatives to traditional agriculture,
particularly for leafy vegetables like
Lactuca sativa
(lettuce). These systems offer precise
control over environmental and nutritional conditions, enabling improved plant performance
and sustainable production. A key factor in hydroponic cultivation is the selection of an
appropriate substrate and nutrient formulation, both of which directly affect water retention,
aeration, nutrient availability, and root development.
Previous research has identified substrates such as rockwool and coconut coir as
effective growing media due to their structural stability and moisture retention capabilities.
Meanwhile, the integration of organic inputs such as humic acid and microalgae into nutrient
solutions has been shown to enhance nutrient uptake and plant growth. This study aims to
evaluate the synergistic effects of different substrate–nutrient combinations on the vegetative
growth and average leaf weight of lettuce under controlled hydroponic conditions.
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In addition to its diversity and culinary utility, lettuce is a rich source of polyphenolic
compounds and antioxidant vitamins A, C, and E (Romani, 2002). It is frequently associated
with chronic disease prevention, including cardiovascular diseases and certain cancers, owing
to its high radical scavenging activity and frequent raw consumption (Husain, 1987; Cartea,
2011). Optimal growth occurs at temperatures between 7°C and 24°C, making it ideal for
many climate zones.
Lettuce is also appreciated for its low content of calories, fat, and sodium, while being
rich in fiber, iron, and vitamin C (Kim et al., 2016). It contains various antioxidant and
bioactive compounds such as carotenoids, phenolics, and anthocyanins, which contribute to
its health-promoting effects (Simko, 2019). Regular consumption of lettuce supports
protection against chronic illnesses and enhances overall diet quality (Nicolle et al., 2004).
Shifting consumer habits and increased interest in fresh-cut salads (Damerum et al., 2020;
Stuart, 2011) have also led to greater demand for lettuce varieties with diverse colors,
textures, and flavors.
Materials and Methods
.The study evaluated the effect of different growing media and
nutrient solutions on the morphological parameters of
Lactuca sativa
leaves, specifically
focusing on leaf length and width. The data presented in Table 1 shows that both the growing
medium and the nutrient solution had a significant influence on leaf size.
The maximum leaf length and width were recorded in the Rockwool substrate under the
Microalgae + Mineral salts treatment, reaching 18 cm in length and 9 cm in width. This was
followed by the Humic acid + Mineral salts treatment in the same substrate, with values of 17
cm × 7 cm. The lowest values were observed in Perlite with Mineral salts only, showing 10 cm
× 5 cm.
In general, the Microalgae + Mineral salts treatment resulted in the largest leaves across
all substrates. Among the growing media, Rockwool consistently showed superior results,
while Perlite demonstrated the least favorable outcomes. (table 3.1)
(table 3.1)
The findings indicate that the combination of nutrient solutions and growing media
plays a crucial role in enhancing the vegetative growth of
Lactuca sativa
. The significant
increase in leaf size observed with the Microalgae + Mineral salts treatment suggests that
microalgae provide additional bioactive compounds, growth stimulators, and improved
nutrient availability that positively affect plant development.
Among the substrates, Rockwool proved to be the most effective, likely due to its
excellent water retention, aeration properties, and stable structure, which create optimal
conditions for root development and nutrient uptake. This aligns with previous research
indicating that Rockwool is highly suitable for hydroponic lettuce cultivation.
The poor performance of Perlite may be attributed to its lower water-holding capacity
and limited nutrient retention compared to other media, which might restrict the continuous
availability of nutrients and water to the plant roots. These results collectively demonstrate
that selecting the appropriate substrate and nutrient combination is essential for achieving
maximum growth performance in hydroponic systems.
To find the average fresh weight of a lettuce leaves, the method of adding three thefts
and dividing the result by three was used. The results were analyzed graphically.
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The weight of the lettuce leaves
Mineral Salts
Mineral Salts+Humic acid
Mineral salts+Microalgae
Vermiculite 20,8 gr 20,4 gr 21,4 gr 24,6 gr 25,4 gr 25,9 gr 29,4 gr 30,5 gr 32,4 gr
Perlite
19,6 gr 19,8 gr 20,3 gr 22,9 gr 23,6 gr 24,4 gr 27,4 gr 27,9 gr 28,6 gr
Coconut
Coir
19,4 gr 20,8 gr 21,4 gr 22,3 gr 23,5 gr 23,8 gr 25,8 gr 26,4 gr 26,7 gr
Rockwool
20,8 gr 21,4 gr 22,7 gr 24,9 gr 25,3 gr 26,3 gr 29,8 gr 31,5 gr 32,4 gr
This result was calculated using the formula for finding the average:
(𝒂 + 𝒃 + 𝒄)/𝟑 = 𝒅
𝒂, 𝒃, 𝒄 − 𝒘𝒆𝒊𝒈𝒕 𝒐𝒇 𝒍𝒆𝒕𝒕𝒄𝒆 𝒍𝒆𝒂𝒗𝒆𝒔
3-
fixed value
d-
average value
The average weight of lettuce leaves grown in vermiculite.
For mineral salts:
(20,8 + 20,4 + 21,4)
3
= 20,866
For mineral salts and humic acid:
(24,6 + 25,4 + 25,9)
3
= 25,3
For mineral salts and microalgae:
(29,4 + 30,5 + 32,4)
3
= 30,766
The average weight of lettuce leaves grown in perlite.
For mineral salts:
(19,6 + 19,8 + 20,3)
3
= 19,9
For mineral salts and humic acid:
(22,9 + 23,6 + 24,4)
3
= 22,966
For mineral salts and microalgae:
(27,4 + 27,9 + 28,6)
3
= 27,966
The average weight of lettuce leaves grown in coconut coir.
For mineral salts:
(19,4 + 20,8 + 21,4)
3
= 20,533
For mineral salts and humic acid:
160
(22,3 + 23,5 + 23,8)
3
= 23,2
For mineral salts and microalgae:
(25,8 + 26,4 + 26,7)
3
= 26,3
The average weight of lettuce leaves grown in rockwool.
For mineral salts:
(20,8 + 21,4 + 22,7)
3
= 21,633
For mineral salts and humic acid:
(24,9 + 25,3 + 26,3)
3
= 25,5
For mineral salts and microalgae:
(29,8 + 31,5 + 32,4)
3
= 31,233
After finding the average weight values, they were analyzed graphically. The graph
shows that the best results were observed for lettuce leaves grown in vermiculite and
rockwool, supplemented with mineral salt and microalgae solutions (diagram 3.2).
(diagram 3.2)
The study evaluated the average weight of
Lactuca sativa
(lettuce) leaves grown in
different substrates (Vermiculite, Perlite, Coconut coir, and Rockwool) under three nutrient
conditions: Mineral salts, Mineral salts + Humic acid, and Mineral salts + Microalgae.
Vermicu
lite
Perlite
Coconut
coir
Rockwo
ol
Mineral salts
20,866
19,9
20,533
21,633
Mineral salts+Humic acid
25,3
22,966
23,2
25,5
Mineral salts+Microalgae
30,766
27,966
26,3
31,233
0
5
10
15
20
25
30
35
На
зва
н
и
е
оси
average weight of lactuca sativa leaves
Mineral salts
Mineral salts+Humic
acid
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The results show that in all substrates, the addition of humic acid and microalgae
significantly increased the average leaf weight compared to using mineral salts alone. The
highest average weight was observed in the Rockwool + Mineral salts + Microalgae treatment
(31.233 g), followed by Vermiculite + Mineral salts + Microalgae (30.766 g). The lowest
average weight was found in Perlite + Mineral salts (19.9 g).
The findings of this study clearly indicate that both humic acid and microalgae have a
positive effect on the growth performance of
Lactuca sativa
, as demonstrated by the increased
average leaf weight. The positive impact of humic acid is likely due to its ability to improve
nutrient uptake, stimulate root growth, and enhance plant metabolism. Meanwhile,
microalgae may contribute through the production of bioactive compounds, growth
hormones, and improved nutrient availability in the growing medium.
Among the substrates tested, Rockwool consistently supported the highest leaf weights,
especially when combined with microalgae. This could be attributed to Rockwool’s excellent
water retention, aeration, and nutrient-holding capacity, creating an optimal environment for
root development and nutrient absorption.
The results suggest that integrating organic supplements like humic acid and microalgae
into soilless cultivation systems can significantly boost lettuce production. Particularly, the
Mineral salts + Microalgae treatment demonstrated superior results across all substrates,
recommending its potential application in modern hydroponic and soilless farming practices.
Conclusion
The results of this study clearly demonstrate that the choice of growing substrate and
nutrient formulation plays a vital role in optimizing the growth of
Lactuca sativa
in
hydroponic systems. Rockwool, due to its superior physical properties, consistently
supported the highest growth metrics. The supplementation of mineral salts with humic acid
and microalgae significantly increased the average leaf weight compared to mineral salts
alone. Among the treatments, the combination of rockwool and mineral salts with microalgae
yielded the most favorable results, indicating the potential of biofertilizers to enhance lettuce
productivity. These findings suggest that integrating organic inputs into soilless cultivation
can lead to more efficient and sustainable lettuce production.
References:
Используемая литература:
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Husain, S.R.; Cilurd, J.; Cillard, P. Hydroxyl radical scavenging activity of Flavonoids.
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