Nutrient cycling potential of 10 alternate forage species compared to bahiagrass: A mesocosm study in Lake Placid FL, 2024.

The purpose of this study was to test if certain species had the potential to remove phosphorus and improve soil health when compared to bahiagrass or bare soil. This study was intended as a starting point to determine if overseeding any of these candidate species into bahiagrass pastures would remove legacy phosphorus and increase organic matter or fix nitrogen.
This mesocosm study took place in January-May 2024 in a shadehouse using 1.7 gallon pots filled with soil extracted from improved bahiagrass pastures at Archbold Biological Station’s Buck Island Ranch in Lake Placid, FL. 10 seeds from 10 alternate forage species were transplanted into a treatment pot, with 3 replicate pots per treatment. The treatments tested were monoculture species in low density (2 individual plants per pot), monoculture in high density (8 individuals per pot), four winter annual species in low density (1 individual of each species per pot: 4 total individuals), four winter annual species in high density (4 individuals per species per pot: 16 total individuals), two summer annual species species in low density (1 individual per pot: 2 total individuals) and two summer annual species in high density (4 individual plants per species per pot: 8 total individuals). Six additional pots were randomly selected for one of two control treatments: bare soil or bahiagrass. The bahigrass control was established by transplanting four rhizomatous sprigs of bahiagrass into each pot.
Nutrient supply rate was measured using Plant Root Simulator (PRS) probes over the course of 9 weeks. Soil properties were measured by collecting soil, air drying, sieving and sending to University of Florida ARL for Mehlich-3 P, water-extractable P, and Mehlich-1 P, Al, and Fe to calculate the Soil Phosphorus Storage Capacity (SPSC). pH was determined with a YSI handheld probe in distilled water and organic matter was measured using the loss-on-ignition method. These soil properties were measured at the start of the experiment and at the end of 9 weeks. Soil water was collected weekly with a leachate reservoir placed under the potted plant. Water samples were analyzed for TKN, ammonium, orthophosphate, and total phosphorus.
At the end of the nine weeks, planted were harvested for aboveground biomass and monocultures were ground for forage tissue nutrient content: % nitrogen, % crude protein, % IVOMD, and % phosphorus. Belowground tissues were isolated and tubes, rhizomes and roots were washed, dried, and then weighed separately for belowground biomass. Roots were scanned fresh and used to determine specific root length.