Effect of Magnetized Water and Sugarcane Bagasse-derived Biochar on the Growth and Chemical Composition of Spinach Grown under Drought Stress (Limited Irrigation) in Greenhouse Conditions

Extended Abstract

Introduction

Water scarcity and drought are becoming global problems, particularly in arid and semiarid regions. Drought stress is one of the factors that negatively affect the quantitative or qualitative growth of plants. changes outside the desired range of environmental factors. Due to the severe limitations of water resources in most regions of the country, moisture stress has been defined as one of the most important stresses adversely affecting plant growth and yield. Drought stress generally occurs when water levels of soil and atmosphere decrease through evaporation and transpiration. Almost all plants are somewhat drought tolerant, but the degree of tolerance varies from species to species. Magnetic water can be one of the promising methods to overcome the problem of lack of water resources, improve the production of agricultural products, and deal with drought stress on the plant in different stages of growth, at the same time, it is environmentally friendly. Adding biochar to the soil is another method of dealing with drought stress, increasing organic matter and, as a result, increasing water retention in the soil. Therefore, this study was conducted to investigate the combined effect of moisture stress, biochar, and magnetic water on spinach growth and chemical composition under greenhouse conditions.

Materials and Methods

A factorial greenhouse experiment in the form of a completely randomized design with three replications was conducted with drought stress at three levels of field capacity (FC), 75% of field capacity moisture (0.75FC), and 50% of field capacity (0.5FC); and four levels (0, 1, 2, and 3% by weight) of sugarcane bagasse-derived biochar prepared at 400 ºC and two types of water including magnetized water and non-magnetized water. The required soil was taken from a depth of 0 to 30 cm of a calcareous soil, air-dried, passed through a 2-mm sieve, and analyzed for physical and chemical properties. Sugarcane bagasse was collected from Imam Khomeini Sugar Factory located in Khuzestan Province and converted to biochar at 400 °C under limited oxygen conditions for 4 h. Magnetic water of 0.21 Tesla was prepared by repeatedly passing drinking water through a water magnetizing device. According to the results of the soil test, nutrient elements were added to the soil. 15 spinach seeds (Spinacia oleracea L., var. Virofly) were planted in each pot and they were maintained in greenhouse conditions. After one month, the number of plants was reduced to 9 in each pot. All pots were treated by the mentioned moisture levels through daily weighing. Drought treatments were started two weeks after planting and continued throughout the growing season for two months. After harvesting, plant samples were prepared and chemically analyzed. Statistical analysis was performed using Excel and SAS statistical software and means were compared using Duncan's test at a probability level of 5%.

Results and Discussion

The results showed that in plants irrigated with magnetized water, the application of 1, 2, and 3% of biochar caused an increase of 3.9%, 7.8%, and 8.3%, respectively in the shoot dry weight of spinach, although the changes were not statistically significant, Furthermore, moisture levels of 0.75FC and 0.5FC in the magnetized water caused a decrease of 3.7% and 15.7%, respectively, and in normal water, it caused 8.3% and 24% decrease in shoot dry weight, respectively. In plants irrigated with magnetized water, application of 1, 2, and 3% biochar compared to the control caused a decrease of 19.2%, 32.5%, and 30.6% respectively in the shoot Cu concentration. Whereas, the use of 2% and 3% biochar caused an increase of 6.2% and 11.9% in the shoot Mn concentration. Applying 0.75FC and 0.5FC moisture stress levels compared to the normal conditions caused a significant decrease of 19.5% and 29.7% in shoot Cu concentration, 21.2% and 21.1% decrease in shoot Fe concentration, and 18% and 20% decrease in shoot K concentration, respectively. Whereas, the mentioned moisture levels caused an increase of 24.7% and 47% in the shoot Mn concentration.

Conclusion

In general, the application of magnetized water compared to normal water significantly increased the shoot Mn and Zn concentration by 3 times and 40.4%, respectively, compared to that of the control. Using magnetized water increased shoot dry weight by 10.8% compared to normal water. The results showed that the application of magnetized water can be used as a suitable solution to increase the concentration of some nutrients and some growth characteristics of spinach. In general, the results showed that the application of magnetized water and biochar, which have been introduced as two strategies to reduce the adverse effects of drought on plants, can be effective on the chemical composition of plants and nutrient concentration of the plant. Further studies are recommended to evaluate the impacts of other biochar derived from livestock manure and plant residues, as well as different levels of biochar, on spinach and other crops, under drought or other stress conditions.