In this study, the effects of water quality on the growth of Lettuce (Lactuca sativa) and Cherry Tomato (Solanum lycopersicum) grown using a hydroponics system is evaluated. Water was collected from different sources, such as Yamuna River water, Irrigation canal water, Lake water and Tap water (RO) and its quality of was evaluated for various physical (TDS) and chemical parameters (pH, Alkalinity, Conductivity, Salinity), including heavy metals , Cadmium and Arsenic. Plants of both the species were raised in hydroponics using diffetrent water sources and harvester after three months of growth. The biomass of plants, shoot and root (Fresh and dry weight) was determined. With regard to physical chemical parameters the Yamuna river water quality was the poorest followed by SNU pond water, Palla Irrigation Canal water and the best RO treated tap water. River water produced Lettuce plants with higher fresh weight, given that River water has the worst quality as per the Standards specified by the Bureau of Indian Standards. The result of this experiment shows how the growth and yield of both the plant species are affected by the quality of water and how the plant growth is optimized under hydroponic conditions. A comparison between the plants grown using hydroponic culture and traditional soil culture using the above-mentioned water samples are discussed.
Crop production using the Hydroponics culture is gaining immense popularity in the recent years, as it is a more efficient way to produce better quality plants in a shorter span of time compared to the traditional soil culture. (Trejo-Téllez and Gómez-Merino 2012)
Water used for irrigation can vary greatly in quality depending upon type and quantity of dissolved salts. Salts are present in irrigation water in relatively small but significant amounts. They originate from dissolution or weathering of the rocks and soil, including dissolution of lime, gypsum and other slowly dissolved soil minerals.
It seems obvious that pure and good quality water is essential for proper growth of plants in hydroponics systems. Through this study, different sources of water have been selected and used for the cultivation of Lettuce and Tomatoes in a hydroponics system.
Materials And Methods
The project was conducted at Shiv Nadar University, Greater Noida, Uttar Pradesh from October 2016 to April 2017.
Seed Germination and Seedling production
Lettuce (Lactuca sativa) and Cherry Tomato (Solanum lycopersicum) seeds were sown into plug trays filled with Horticultural Perlite. Water was sprayed using a pressure sprayer on the perlite mix twice-a-day to maintain moisture in the perlite mix, at this germination stage. At the end of the 21st day, 2-3 mL of Diammonium Phosphate, ((NH4)2HPO4) the most widely used phosphorous fertilizer was added individually to the seedlings to improve their nutrition and strength. The seedlings showed a prominent improvement in health and turned a lot greener within 2 days’ time.
The seedlings were transplanted into growth slabs containing coco peat after 28 days from the germination, when the plants had three true leaves. (Azarmi, Gikloo and Taleshmikail 2010)
The seedlings have to be carefully placed into the coco peat pellets, which were soaked in water for 30-40 minutes, using small tweezers. (Nguyen, N. T., McInturf, S. A., Mendoza-Cózatl, D. G. 2016). The transplanted plants in the coco peat pellets placed in net pots have to be sprayed with water using a pressure sprayer for another 10 days for the roots to emerge out of the coco peat slabs. Once the roots were long enough, the coco peat slabs in the net pots were transferred to the hydroponics system.
Hydroponics Culture Stage
Eight Hydroponics systems (each having the capacity to house 20 plants) was set up using the following materials: Water Reservoir - Planter 20L Capacity, Air Pump, Air Stone/ Air Diffuser, Net pot holding plate and Net pots.
The Hydroponics technique adopted for this experiment was the Deep-Water Culture, the method in which the plant roots are suspended in a solution of nutrient-rich, oxygenated water saturated from the air pump combined with porous stones. With this method, the plants grow much faster because the roots directly receive high amount of oxygen. (Zeroni, Gale and Ben-Asher 1983)
Modified Hoagland’s solution was prepared for all the systems using the chemicals, KNO3, K2SO4, (NH4)2SO4, (NH4)2HPO4, Ca(NO3)2, CaSO4, Potassium Phosphate, and MgSO4. The plants were arranged in the hydroponics system.
Water samples were collected from 4 different sources, which are given below:
- River water from the Yamuna River, near Kalindi Kunj, New Delhi.
- Irrigation canal water from Palla Village, near Tehsil Dadri, Greater Noida.
- Lake Water from Lake SNU, Shiv Nadar University Campus, Greater Noida.
- Tap Water (Treated Water) from Shiv Nadar University Campus, Greater Noida.
The Hydroponic Systems were setup as a deep-water culture. In each of the system, 2000mL of one of the above water samples and 200mL of modified Hoagland’s solution was added to prepare the nutrient solution. One water sample was used in 2 Hydroponics systems. The air pumps were connected to the hydroponics systems using an air stone which was placed at the bottom of the planter. The air pumps were run 24 hours every day to supply fresh oxygen to the nutrient solution. The nutrient solution had to be changed every fortnight.
Harvest and Analysis of plants
The Lettuce plants were harvested at the end of 31 days and the tomato plants were harvested at the end of 45 days. The fresh weight of the shoots and roots were measured. The number of leaves and the height of the plant was measured. Then the plants were placed in the oven at 60°C overnight and the dry weight of the root and shoot was measured.
Water Quality Analysis
According to the procedures provided in the Central Pollution Control Board’s Manual on Water and Wastewater Analysis, the following parameters of water quality were evaluated.
- Heavy metals : Cadmium and Arsenic
RESULTS and DISCUSSION
The quality of water assessed in the experiment in increasing order was as follows, the Yamuna river water, Lake SNU water, Palla Irrigation Canal water and Treated tap water. The Conductivity of Tap water and Canal water is considered to be of excellent quality for irrigation water as per the Bureau of Indian Standards for Irrigation water quality. (IS: 10500: 1991 n.d.)
All the water samples had a relatively higher pH value compared to the optimum value of 5-6 for Hydroponics Systems and the TDS of all the water samples is also within the permissible limit for irrigation quality water. Yamuna River had very high lead content which is higher than the permissible limit of 0.05 mg/L set by the Bureau of Indian Standards. All the water samples had high Cadmium content. According to Azarmi et al, the growth parameters of plants improved with increasing salinity and it is reflected here. River water having salinity value of 0.5 ppm showed a significantly better growth rate compared to the other water samples. Canal water has all the parameters close to the desired limits for irrigational water provided by the Bureau of Indian Standards (IS: 10500: 1991 n.d.) and it has reflected in a favorable growth of Lettuce and Tomatoes.
Lake water showed a mortality rate of 25% in the growth of Lettuce and 12.5% in the growth of Tomatoes. The high pH value and alkalinity of lake water should have had an impact on the survival of the plants in early stages. It can be concluded that water with high pH is not suitable for growth of plants in a Hydroponics Systems. The River water had produced Lettuce plants with higher fresh weight, given that River water had the worst quality as per the Standards specified by the Bureau of Indian Standards.
The dry weights of Lettuce plants shows that the growth of plants in Tap water is more uniform than in the other treatments. The growth of plants in the River and Canal water treatments was non-uniform and the difference in the growth parameters of one plant to the other in the same treatment was very high.
So, based on our experimental study, we can conclude that use of pure and good quality water reflects in consistent growth of plants whereas water with suitable amount of salt content and optimum pH value reflects in growth of plants with higher fresh and dry weight, much higher than the plants, grown using Treated tap water. High amount of pH and Alkalinity is not suitable for the growth of plants in a Hydroponics system.