Design and development of laboratory scale hydroponic system for growing sweet basil using plasma activated nutrient solution
Creators: name: Date, Manasi Bhalchandra
Publisher: name: No Publisher Supplied
Year: 2020

description: Food security for future generations has become a critical issue for a variety of reasons such as population explosion, climate change, and less land for crop cultivation. Alternative growing techniques such as hydroponics which do not involve the use of soil for crop production can be used on commercial level to alleviate the food security problem. In our research, sweet basil was grown using plasma activated nutrient solution (PANS) in a closed hydroponic system. The PANS offers number of benefits over nutrient solution (NS) for basil growth due to the presence of reactive oxygen and nitrogen species. PANS was prepared using a gliding arc plasmatron system developed by Drexel University and was characterized by measuring its pH, EC (electrical conductivity), ORP (oxidation-reduction potential), and reactive species concentrations.To assess the effect of PANS on sweet basil plant growth and quality, basil seedlings were grown using Rutgers Devotion DMR cultivar seeds in a growth chamber for 14 days (25 °C, 75 % relative humidity, and 100 µmol/m2s light intensity). These seedlings were then transferred to custom-built NS and PANS chambers for 20 days growth period. The two chambers were identical and were assembled in the pilot plant of Rutgers Food Science building. The plants received fixed amount of light (250 µmol/m2s) for 16 h each day and they were watered 8 times a day for 8 mins at a time, throughout the harvest period. The temperature, the relative humidity, the CO2 level inside the two chambers, and the temperatures of NS and PANS were monitored every 1 h. To evaluate the effect of PANS, two treatment variations were done while growing the basil plants in the two chambers. In Treatment 1, the NS and PANS solutions that were prepared on day 1 of the harvest period were used throughout the 21-day growth period to water the basil plants whereas in Treatment 2, fresh NS and PANS solutions were used to water the plants for week 1, week 2, and week 3. For both the treatments, the basil plants were harvested on the 21st day and their growth parameters such as plant height, number of branches, number of nodes, root length, leaf index, mass yield, and quality parameters such as leaf color, texture, microbial quality, aroma profile, and tissue nutrient content were evaluated. The growth of algae in the solutions was also estimated at the end of every week.Results showed that basil grown in PANS had higher growth and some improved quality parameters compared to basil grown using NS. PANS Treatment 1 (PANST1) had the most significant effect on the basil plants with increased height (11 %), more number of branches and nodes, and higher mass yield (35 %). PANS Treatment 2 (PANST2) resulted in basil leaves which had higher green (a*) value and higher leaf index. Peak rupture force, leaf toughness, and Young’s modulus values for basil leaves were not significantly different between PANST1, PANST2, and control. Aroma analysis of the basil leaves showed that PANST1 resulted in an increased formation of methyl eugenol and eugenol, possibly indicating a spicier aroma from the leaves. Significant algae reduction (41 % and 45 %, respectively) was observed in PANST1 and PANST2 after first 2 weeks. However, at the end of week 3 only PANST2 showed significant algae reduction (45 %). In terms of microbial quality, it was found that both PANST1 and PANST2 treatments did not show any significant difference in total plate count of the basil leaves, when compared to control. The results from the tissue analysis indicated no difference in the tissue nutrient profile for both the treatments when compared to control. Energy wise, the growth of basil by control treatment required 73.9 kWh total energy, whereas PANST1 treatment required 74.9 kWh and PANST2 treatment required 76.9 kWh. This study showed that growing Rutgers Devotion DMR sweet basil using PANS resulted in higher (11 %) growth, higher yield (35 %), darker green color, and an altered aroma profile in the basil leaves. Growing sweet basil under PANST1 was better for plant height, number of branches, number of nodes, basil yield, and aroma profile. Use of PANST2 was better for greener leaf color, higher leaf index, and more algae removal. Thus, use of PANS appears to show a promise for growing basil hydroponically. Further research is needed for scaled-up operations at a greenhouse scale.