The effect of a non-ionic surfactant on the growth and development of tomato and wheat plants under deficit irrigation

Abstract

The use of surfactants in plant production is becoming increasingly popular in the agricultural sector. Non-ionic surfactants (NIS) are being used for water conservation as well as the improvement of plant growth factors, such as biomass accumulation, plant development and economic yield. The effect that plant surfactants have on crop physiology is not well understood, with little research outside of commercial trial work. This may be due to the focus being on the effects of NIS on soil and water qualities, rather than the crop itself. The trial work sought to identify if a NIS may have a noticeable effect on measurable parameters such as germination, chlorophyll content, physiological development, growth cycle and economic yield. The parameters were compared to control at various irrigation rates to establish if any key differences exist. To cover the full growth cycle of two types of crops, namely wheat as a monocot and tomato as a dicot, the trial work was separated into three distinct methodologies. The germination parameters were measured under laboratory conditions within a germination incubator to control temperature, light, and moisture. The wheat parameters were determined in a greenhouse pot trial where temperature, moisture and space were regulated. The tomato parameters were, as with the wheat measured within a greenhouse under temperature, moisture, and space control. The germination data of the trial showed a lack of consistency between the two crops. Both crops were subject to increasing levels of NIS (0.06, 0.12, 0.24 and 0.48%) and compared to a control where distilled water was used. The results seem to indicate that mild germination inhibition may occur on wheat seeds as NIS dosage is increased. The tomato germination showed an improvement of germination at the half (0.06%) and double (0.48%) NIS dosage which contrasts both the literature and the results of the wheat. The wheat and tomato greenhouse pot trial both showed deviation from the hypothesis for several growth parameters. Both crops were subjected to control (100% irrigation) and water stressed (75 and 50% irrigation) with or without the addition of a NIS. Several of the wheat parameters were similar between the control and NIS treatments, where others did not demonstrate a clearly defined trend. Effects of the NIS were more clearly observed in the once-off cumulative data parameters rather than the weekly readings. The tomato trial shows the first season of production having a greater correlation with the available literature, where the second season showed a greater degree of variation. It is important to note that during both the first and second seasons of the greenhouse trial, there were technical challenges faced in the form of the greenhouse where the temperature and humidity may have been altered. It is also possible that the different dates on which the ix trials took place may have affected the outcomes as well as the advent of problems arising from the Covid-19 pandemic during the strict lockdown measures in March and April 2020.The trial work indicate that non-ionic surfactants may have measurable effects on plant physiology, although further research is needed to better understand this aspect of the technology