Ditch plant response to variable flooding: A case study of Leersia oryzoides (rice cutgrass)

Abstract:

Vegetated drainages are an effective method for removal of pollutants associated with agricultural runoff. Leersia oryzoides (rice cutgrass), a plant common to agricultural ditches, may be particularly effective in the remediation process; however, responses of L. oryzoides to flooding are undocumented. The objective of this greenhouse study was to characterize responses of L. oryzoides to various soil moisture regimes representative of agricultural ditches, including four treatments ranging from well drained to saturated. Over the eight weeks of the study, plants were subjected to four flooding regimes that included a (1) well-watered, well-drained control; (2) well-watered, well-drained intermittently flooded treatment; (3) partially flooded treatment; and (4) continuously flooded treatment. Decreases in photosynthesis occurred only when soil redox potential (Eh) dropped below +350 mV (all flooded treatments). Although flooding reduced belowground:aboveground bio-mass ratios, overall productivity and root development were unaffected. Results indicated that management practices increasing retention time in agricultural ditches would not reduce productivity in L. oryzoides until soil oxygen is depleted for sufficient duration to induce reduction.