The increasing population of the world has something to put on priority. More people means more food to produce with a very limiting and decreasing resources; the possible way to sustain the left resources for the next generation must have the combination of small production area and lower inputs on farming while at the same time making still a higher output as possible.

Hydroponics is one of the most successful and specific technologies for high-volume production. Controlling water supply, pH, ambient temperature, insect and disease infestation, reducing labour, wind velocity, increasing density spacing and yields due to less rivalry among roots and no requirement for soil sanitation are all important advantages of growing without soil. A nutrient solution for hydroponic systems is an aqueous solution containing mainly inorganic ions from soluble salts of essential elements for higher plants (Steiner 1968).

Synthetic (or refined mineral, or salt-based) and organic-based formulations are the two types of hydroponic fertilizer formulations. Humans have created soluble salts for plant uptake that are referred to as a synthetic nutrients. Because the structure and properties of all the components differ, they dissociate in the ‘universal solvent’ at various speeds resulting in a modest pH change. This is the most significant difference between synthetic and natural nutrient sources although it may be overcome with time and skill. There is no difference in the end ion product between synthetic and organic-based nutrition products. Just a different means of getting food to the plant is what it is. Plants consume ions in an inorganic form. In other words, when these things have been dissolved in water, plants ingest the inorganic elements of these materials such as guano and kelp ions.

Lettuce (Lactuca sativa L) is one of the most economically important leafy vegetables in the world and its production is currently increasing due to the growing interest in healthy food (Shatilov et al 2019). Since the concept of green products has been prevailing worldwide, lettuce has gained importance not only for food application but in various formations having other specific uses (Das and Bhattacharjee 2020). Hydroponic growth of lettuce is considered to be quite easy requiring less skill from the grower. This makes it a widely grown commercial hydroponic crop with many varieties performing well under a variety of conditions (Jenner 1980). The cultivation of lettuce in a hydroponic system requires a nutrient solution within specific target ranges for a multitude of water quality parameters.

In the present study, different fertilizers were used which were economically available in the market and had the potential for growing hydroponic lettuce plant like masterblend (for lettuce and tomato), SNAP (simple nutrient addition programme) solution and humus foliar fertilizer. Besides this study also focused on determining which would give a better quality crop between aerated and non-aerated conditions.

The research was carried out at Isabela State University’s crop science laboratory area, Matusalem, Roxas, Isabela. In order to give some temperature control, prevent evaporative water loss, manage diseases and pests and shelter the crops against weather elements such as wind and rain, an improvised greenhouse was built.

Preparation of seedling plugs: For the seedling stage, lettuce seeds were placed in shallow plastic trays with drainage holes and a 25:75 ratio of vermicast and rice bran ash was utilized as growing media. Individual plants were pricked or transplanted into 8-oz styrofoam containers after 20 days of seeding. Six vertically sliced 3 millimeter wide cuts were made in the bottom of each cup for roots to grow down into the nutrition solution. For the entire study period, the cup was filled with chopped abaca fiber (approximately 1/3 full) which was utilized as a growing medium for the lettuce plants.

Preparation of culture troughs: A round black basin with a diameter of 62 centimeters was used in the mixing of the nutritional solutions with water. These basins served as containers of the growing nutrient source for the plants. Twelve holes equidistant from one another were made on the styroboard enough to hold in place the seedling plug by its neck.

Preparation of solution and treatments: The snap nutrient solution was prepared by mixing it with 19 liters of water likewise with the masterblend fertilizer (lettuce and tomato). Humus was diluted first in a small amount of water and served as liquid fertilizer. All fertilizers were used following the recommended rate.

The treatments were designated as follows:

Factor A (aerated) comprised Factor B treatments viz T₁ [Control (water only)], T₂ (RR- 50 ml SNAP solution + 19 liters of water), T₃ [RR- 25 g masterblend (lettuce) fertilizer + 19 liters of water], T₄ [RR- 30 g masterblend (tomato) fertilizer + 19 liters of water] and T₅ (RR- 30 g humus foliar fertilizer + 16 liters of water) whereas Factor A (non-aerated) comprised T₁ [Control (water only)], T₂ (RR- 50 ml SNAP solution + 19 liters of water), T₃ [RR- 25 g masterblend (lettuce) fertilizer + 19 liters of water], T₄ [RR- 30 g masterblend (tomato) fertilizer + 19 liters of water] and T₅ (RR- 30 g humus foliar fertilizer + 16 liters of water).

Proper care and management were done throughout the whole duration of the experiment to have accurate results. The occurrence of pests and diseases was minimized by applying proper sanitation. Fish net with small holes was installed in the greenhouse to prevent the entry of pests. Shading of the greenhouse was done to lessen much exposure of lettuce plants to heat of sunlight and to make the greenhouse a little bit cooler. To minimize the germination of weed seeds and water evaporation, the indoor ground of the greenhouse was mulched with rice straw.

After 35 days of planting, the harvest was completed. The entire plant was uprooted by hand and the stems were then pruned with a pruning shear just below the plant’s lowest leaves. Ten sample plants in each treatment were used for the data. Height of each plant was measured at 35 days after planting. Measuring was done from the base of the plant up to the tallest leaf of the lettuce using meter stick.

The number of leaves per ten samples was counted and divided by ten to obtain the average number of leaves per plant. For calculating average weight of the whole plant, the weight of ten sample plants was determined with the use of digital weighing balance and divided by ten to obtain the weight per plant. The pH of the solution was recorded after the conduct of the study to determine the status of the solution. The cost and return analysis of using different fertilizers was computed after the conduct of the study.

Plant height: The height of the plants at 35 days after transplanting was significantly affected by the different treatments employed (Table 1). In the main plot, in the aerated condition, the plant height was 25.21 cm as against 18.07 cm in non-aerated condition. In aerated, the comparison in all treatment means showed that the different nutrients had influenced the height of the plants with means ranging from 8.46 to 37.01 cm. The tallest plants were in the treatment T₄ [Masterblend (tomato)] with a mean of 37.01 cm. Under non-aerated condition the means ranged from 6.63 to 26.60 cm and the tallest plants were produced in the treatment T₄ with a mean of 26.60 cm. In two sub-plots (average all over main plot), under aerated and non-aerated conditions, T₄ recorded taller plants (37.01 cm) than the non-aerated condition (26.60 cm) followed by T₃ [(Masterblend lettuce)] (35.11 and 25.17 cm in aerated and non-aerated conditions respectively) and T₂ (SNAP) (29.76 and 24.44 cm in aerated and non-aerated conditions respectively). The height of plants at 35 days after transplanting as affected by the two conditions was statistically significant based on the analysis of variance.

The reason behind it might be that plants grown hydroponically with aeration had a greater outcome when plants absorbed dissolved oxygen in water (Goto et al 1996), also to be a great method for keeping one’s water and fertilizer mixed and preventing the fertilizer from settling to the bottom of the reservoir. When plants grown hydroponically and depletion of dissolved oxygen occurred, it affected the plant growth negatively (Roosta et al 2016).

Average number of leaves: The number of leaves per plant is shown in Table 2. Under main plot, there was no difference between aerated and non-aerated conditions with respect to number of leaves. The number of leaves produced by the plants applied with different fertilizers had significant differences with means ranging from 4.60 to 12.20 under aerated condition; T₄ resulted in the highest number of leaves with a mean of 12.20 and T₅ with a mean 4.60 as the least. In non-aerated condition, T₄ had maximum number of leaves (8.07) and T₁ (Control) the least (4.23). In case of two sub-plots (average all over main plot), the T₄ treatment under aerated condition was having the maximum number of leaves (12.20) which was significantly higher than the non-aerated (8.07) followed by T₃ [Masterblend (lettuce)] with 9.37 and 7.63 leaves in aerated and non-aerated conditions respectively. Based on the analysis of variance, all treatments of factor B were statistically significant but non-significant for Factor A (main plot). But in the main plot, aerated or non-aerated condition did not tend to increase the number of leaves per plant.

Average weight of the whole plant: The effect of different fertilizers under aerated and non-aerated showed better efficiency in terms of the weight of whole plant (Table 3). The analysis of variance revealed significant differences. In the main plot the average weight was higher in aerated condition (71.04 g) as compared to non-aerated (50.08 g). In two subplots, T₄ resulted in more average weight of whole plant (116.93 g) as compared to non-aerated (69.32 g) followed by 112.13 and 75.94 g in T₃ in aerated and non-aerated conditions respectively which were statistically significant. Based on the analysis of variance, all treatments of factor A and B were statistically significant.

In these findings, aerated plants gained more weight than non-aerated plants implying that when plants absorb the necessary nutrients and are given a favorable environment, they gain more fresh weight. Aeration of the nutrient solution promoted plant development in several species; a lack of aeration has also been found to be a limiting factor in plant growth (Durell 1941).

pH of the solution: The pH is a parameter that measures the acidity or alkalinity of a solution. This value indicates the relationship between the concentration of free ions H⁺ and OH present in a solution that ranges between 0 and 14. In this study, a hydroponic pH indicator was used to determine the pH of the solution. pH of the solution in aerated and non-aerated was taken before and after the conduct of the study (Table 4). The same trend of pH was obtained by aerated and non-aerated before the conduct of the study. While non-aerated obtained uniform pH after the conduct of the study, aerated treatment obtained neutral pH of 7 and treatments T₂, T₃, T₄ and T₅ obtained the same pH of 8 (means alkaline).

Cost and return analysis: The cost and return analysis of growing hydroponics lettuce is shown in Table 5. This was taken by converting the circumference of the basin into an area of 0.1225 m², the size of the greenhouse which was 7 x 3 m² less the 0.5 meter alleyway with the total of 17.5 m² divided by the area of the basin with 0.1225 m². The quotient is 143 sets of 0.1225 m² to occupy the area of the greenhouse. In descending order, plants grown in aerated condition, T₄ attained the highest return on investment with 77.97 per cent. It was followed by the plants grown in T₃ with 75.69 per cent and T₂ with 28.75 per cent and the rest obtained negative return of investment. In non-aerated, T₃ obtained the highest return of investment with 37.13 per cent followed by T₄ with 21.09 per cent and T₂ with 12.20 per cent and the rest obtained negative return on investment.

The study showed that the growth performance of lettuce was highly affected by the fertilizer masterblend (tomato) as source of nutrients under aerated condition. Using humus foliar fertilizer was not suitable for hydroponic growing of plants in both conditions. It is further concluded that masterblend (tomato) fertilizer had a greater advantage over the other fertilizers for growing hydroponic lettuce thus attaining higher return on investment.

Means within a row represented by common letters are not significant at 1% LoS;

Highly significant

Means within a row represented by common letters are not significant at 1% LoS;

Highly significant

Means within a row represented by common letters are not significant at 1% LoS;

Highly significant

The cost of production and yield per basin were multiplied by 143 to get the RoI of an area of 21 m² greenhouse

References