Rice cutgrass growth as affected by simulated flooding and water nitrogen concentration under greenhouse conditions

Abstract

Practical challenges exist in minimizing the ecological impact of conventional agricultural systems, which often depend upon the intense usage of irrigation and agrochemicals in order to maximize the level of food production. Significant amounts of nitrogen fertilizer is lost and transported into drainage ditches. Increasingly, research has focused on the efficacy of plants to mitigate and diffuse agricultural runoff in drainage ditches to better manage and protect fresh water. By assessing plant responses, we will gain a better understanding of specific services a particular species may offer as a buffer plant. The objective of this greenhouse study was to determine the growth and physiological responses of a ditch plant, rice cutgrass (Leersia oryzoides), to a range of flooding and nitrogen input regimes, in order to gain a better understanding of why this species is well adapted to ditch environments. The experiment was a complete 3 × 3 factorial design with three levels of flooding intensity and three levels of nitrogen addition in the form of ammonium nitrate (NH₄NO₃-N). Each treatment was replicated 15 times for 135 plants total. The study was terminated six weeks after flooding treatment initiation. Plants were able to modify their physiological responses in order to withstand environmental stress. When grown in partially flooded conditions, individuals produced more aboveground (37.52% and 38.42%) and belowground biomass (48.05% and 87.81%), compared to other treatments (control and continuously flooded, respectively). There was a 58.5% and 30.1% increase in shoot-to-root ratio as both flooding and aqueous nitrogen concentration increased. The increased productivity of rice cutgrass in partially flooded treatments and its capacity to survive increased nitrogen concentrations may explain the persistence of this species in agricultural ditches.