Effects of Magnetized, Chelated Iron Foliage Treatments on Foliar Physiology, Plant Growth and Drought Tolerance for Two Legume Species

Abstract

A greenhouse study was conducted to determine the effects of foliar applications of magnetized, chelated liquid iron fertilizer for increasing the drought tolerance of two legumes. Study objectives were to determine the drought tolerance effects of four treatments on foliar gas exchange, soil moisture, and plant growth for velvet bean (Mucuns pruriens) and soybean (Gylcine max) plants. The four foliage treatments included applications with chelated liquid iron fertilizer (2.5 and 5%) with a conventional boom sprayer, with and without magnets in the spray lines. Physiological measurements were collected before foliar treatments and again after a 24-day deficit irrigation schedule. Physicochemical water properties were measured for each of the foliar treatments. Photosynthesis rates were 5.98, 2.04 and 3.19 µmol/m2/s for the control, non-magnetized and magnetized fertilizer treatments (2.5%), respectively, after completing the deficit irrigation schedule. Instantaneous water use efficiency (IWUE) was 0.60, 0.28 and 1.02 for the control, non-magnetized and magnetized fertilizer treatments (2.5%), respectively, after completing the deficit irrigation schedule. Photosynthesis and IWUE increased 56 and 263% for the magnetized fertilizer treatment (2.5%) compared to the non-magnetized foliar treatment, when averaged across both legume species. Photosynthesis and IWUE increased as electrical conductivity increased and oxidation reduction potential (ORP) decreased in absolute terms. A single foliar application resulted in aberrant physiological responses that are contrary to very widely held plant defense theories involving abiotic stressors. The single application improved the photosynthesis and water use efficiency for water stressed legumes emphasizing the need to better understand the relationships between water quality, plant bioenergetics, and stress physiology. Improved drought tolerance in row crops such as dry beans and soybeans, with a single magnetized fertilizer application, would be cost effective and easily adapted into current cropping systems. Interactions among physicochemical water properties, bioenergetics, plant metabolism, and crop stress physiology need to be further investigated in order to improve the quality of irrigation water to enhance drought tolerance of field crops.