Bioelectromagnetics for improved crop productivity : an introductory review with pilot study of pre-sowing treatment of tomato

Abstract: Various electromagnetic (EM) treatments has been investigated for their potential in improving crop productivity over the past century. There is today an increasing amount of scientists advocating EM treatments as an organically compatible method for improving plant growth and yield. However, failure to produce repeatable effects and defining causal mechanisms has made it a study of much controversy and debate. The subject requires indepth interdisciplinary knowledge, making it inaccessible for the majority of biologists, horticulturists and growers. In this combined literature review and pilot study, these issues are addressed by providing a comprehensive introductory review of the topic plant bioelectromagnetics and its potential horticultural usability. A vast amount of literature has been reviewed to assess the nature of electromagnetic fields (EMF), what effects of horticultural relevance has been observed, what the fundamental mechanisms behind studied effects might be, and ultimately the potential of using EM treatments for improved crop productivity. A pilot study investigating the effects of an EM pre-sowing treatment of tomato, Solanum lycopersicum, seeds is also presented both as a means of assessing the usability of EM treatments and providing an example of a study in bioelectromagnetics. In the pilot study, a 50 Hz non-uniform sinusoidal EMF of 160, 40 and 9 mT was used to treat the seeds for 15 or 30 minutes, with un-exposed seeds as controls. The exposure was also set in three background static magnetic field (SMF) conditions; one where Ion Cyclotron Resonance conditions for calcium were met (65.8 μT), one where they were not (68.5 μT) and one where only the natural geomagnetic field was present (46.9 μT). The results indicate that a background SMF of 65.8 μT has a significantly inhibitory effect on germination of S. lycopersicum (p<0.01), while the EMF exposure had no significant effects on germination or subsequent growth. It should however be noted that this data is indicative and needs further validation with better experimental conditions. The literature review found that EM treatments have shown many horticulturally interesting effects on plants, and that EM treatments has the potential for horticultural use. However, since they are hard to predict and reproduce it is proposed that extensive species-specific and exposure-specific research should be conducted prior to field application. Many biological effects and mechanisms has also been described and proposed, but much is still debated and more research is needed in these areas since they are key in improving the predictability and accuracy of EM treatments.