Gypsum and water management interactions for revegetation and productivity improvement of brackish marsh in Louisiana

Abstract

A field study evaluating the effects of gypsum and water management on the survival, yield, and protein content of selected species of marsh vegetation was conducted on an open area inundated by brackish water near Hackberry, Cameron Parish, Louisiana. The overall growth and yield response of four species of marsh vegetation: joint grass (Paspalum vaginatum SW.), marsh hay cordgrass (Spartina patens Muh L.), salt grass (Distichlis spicata L.), and American three square (Scirpus americanus Pers.) to gypsum addition (0 versus 7 Mg/ha) and water management (flooded versus non‐flooded plots) were statistically evaluated.

Soil drying was detrimental to the overall growth and yield of all marsh vegetation. There was zero plant survival in the non‐flooded plots except the marsh hay cordgrass with a survival rate of 32.8 %.

Plots receiving 7 Mg gypsum/ha had significantly higher dry matter production than the control. Gypsum application increased dry yield of joint grass (5.44 to 8.08 Mg/ha), marsh hay cordgrass (1.90 to 6.91 Mg/ha), salt grass (0.97 to 2.79 Mg/ha) and three‐square (1.55 to 2.84 Mg/ha) in flooded plots. The yield of marsh hay cordgrass, the only surviving species in the non‐flooded plots, produced a yield increase of 0.40 Mg/ha in response to gypsum. Significantly higher survival rates were observed in flooded plots treated with gypsum than in the non‐flooded plots receiving no gypsum. The mean survival rate for the gypsum‐ treated plots was 68.2%, as opposed to 21.9% for the untreated plots.