Enhancing Agricultural Productivity by using Cold Atmospheric Pressure Plasma

Abstract

It is well known that various technologies are being used and researched to increase the productivity of essential food and agricultural products due to the gradually increasing population, decreasing arable land, and climate change. For the past few years, various research works have been carried out to increase agricultural production, improve the quality of seeds, increase plants as well as preserve the produced fruits for a long time without letting the quality degrade by using plasma. Plasma refers to matter showing collective behavior due to its ionized state, which is also called the fourth state of matter after solid, liquid, and gas. It is found naturally on earth as the flash seen when lightning strikes. In this research, naturally occurring plasma in the atmosphere has been produced in three different ways in the laboratory. The cold atmospheric pressure plasma produced in such a way has applications in a wide range of sectors for various purposes, including electronics, food safety, bio-medicine, agriculture, environment, and material science. With the global population growing and agricultural land diminishing, challenges like slow seed germination seedling growth, and crop loss intensify. Nepal is an agro-based economy and addressing agricultural issues is paramount. However, reliance on chemical fertilizers and pesticides harms the soil and environment. Research into cold atmospheric pressure plasma offers promising solutions. In any application involving plasma, the primary concern is ensuring the availability of plasma for the intended purposes. Plasma production requires a high-voltage power source as a prerequisite, after which applications can be explored. In this context, research into the production and application of cold atmospheric pressure plasma holds significant relevance, especially in addressing the aforementioned agricultural problems. Our study focuses on addressing problems for enhancing germination, seedling growth, and agricultural productivity and prolonging their freshness and bacterial decontamination of irrigated water by employing plasma directly and indirectly, to speed up seed germination, better seedling growth as well as improve yield, prolonging greenness and freshness of green leaves and remove contamination from water. Treating the water with plasma enriches the nutrients (such as nitrate/nitrite) in addition to bacterial decontamination caused by hydrogen peroxide. For plasma production, a fabricated power source made of readily available materials in the local market is capable of producing atmospheric pressure gliding arc discharge which is crucial for those institutions aiming to establish a plasma lab without high operating cost. Additionally, dielectric barrier discharge and plasma jet are produced using a commercially available power supply. The produced plasma is characterized using optical and electrical techniques, adhering to the classical relationship of electron excitation > vibrational > rotational temperature. These plasmas are applied to enhance agricultural production of cauliflower, potato, Basmati rice, and green leafy vegetables through direct (exposure directly on seeds) and/or indirect (exposure to water and then using this water for irrigation) approaches. The duration of plasma exposure significantly impacts several physico-chemical parameters of water, including the pH, electrical conductivity, total dissolved solids, oxidation-reduction potential, temperature, hydrogen peroxide, and the concentration of nitrite and nitrate. As activation time increases, the pH values of water decrease while other physico-chemical parameters increase synchronously. Wheat seed wettability increases and contact angle declines noticeably with a longer treatment time of plasma-activated water used for soaking seeds and direct exposure of plasma which is measured by wettability relation and a self-made prototype goniometer calibrated with a Ramé-Hart goniometer. Plasma-activated water accelerates the germination parameters of cauliflower (Brassica oleracea) compared to untreated crops. The seed’s wettability is significantly enhanced as the treatment duration increases in plasma-activated water. Basmati rice produces the highest level of seed germination, longer seedling shoots, and heavier plants using plasma-activated water. While for green leafy vegetables, it is observed that plasma-activated water, results in improved germination, production, and greenness. Similarly, the production of oyster mushrooms is beneficial by plasma-treated spawn. Direct plasma treatment also eliminates soluble bacteria like Scleropages aureus and Escherichia coli in water. Plasma-activated water reduces chlorophyll retention in detached Tejpat (Cinnamomum tamala) leaves compared to untreated water and accelerates the dormancy of potatoes. The detached Tejpat leaf could be preserved for longer times than normal water using plasma-activated water. The primary cause of these changes is the physical reaction of the plasma on the surface of the seeds and water, resulting in heat, shock waves, a strong electric field, and the presence of reactive oxygen and nitrogen species. These plasma applications demonstrate the potential of both direct and indirect methods to overcome declining agricultural production. Hence, cold atmospheric pressure plasma treatment enhances production, accelerates seed germination, retains chlorophyll in detached leaves, and sterilizes water for potential agricultural use. However, prolonged exposure to direct plasma and plasma-activated water can adversely affect agricultural commodities, necessitating optimization. As conventional fertilizers used in agriculture are not economically and environmentally friendly, plasma-based techniques offer a promising alternative for increasing agricultural production and establishing a more sustainable system in agricultural areas.