Soil subsidence of peatlands occurs worldwide due to drainage. The Everglades Agricultural Area (EAA), located in South Florida, has been drained for agriculture since 1914, with subsidence resulting in shallow soils in certain areas. The purpose of this study is to determine the impact of water management strategies on soil oxidation and N release as affected by differences in proximity to the bedrock. Oxidation rates (CO 2 efflux), as well as CH 4 and N 2 O emissions, were measured in lysimeters filled with shallow and deep peat subjected to four water treatments. Additionally, NO 3 -N, NH 4 -N, soluble organic N, and dissolved organic C were measured in leachate obtained from the collected soils. Average annual emissions from constantly drained soils were 298 g CO 2 -C m -2 yr -1 , with most of the oxidation taking place between June and October. Short flood cycles increased annual oxidation rates compared with constantly drained soils, which had the second highest oxidation rate. Constantly flooded soils had the lowest annual oxidation rates, followed by summer flooded soils. Total N lost in leachate was highest for constantly drained soils, with NO 3 being the dominant form. The deep soils had higher losses of soluble N and C, whereas NO 3 losses from shallow soils were higher. Soil oxidation rates did not differ depending on proximity to the bedrock. We conclude that strategies that avoid short flooding cycles and include crop rotations that allow flooding during summer can reduce oxidation and N losses in leachate from EAA peats.

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The application of agrichar derived from organic feedstocks has the potential to improve soil fertility and crop production by providing major nutrients like phosphorus (P) to the crop, and in some cases also reducing P leaching. The effect of agrichar on the leaching of P in soils is not uniform and can vary depending on the type of agrichar and amount applied. The objective of this study was to (i) evaluate the behavior of four agrichars (rice hulls RH, palm fronds PF, horse bedding HB, and bagasse BG) for their ability to retain/release P and (ii) determine the effect of wet sonication on P sorption behavior. The feedstocks were torrefied at 500 °C using a top-lit updraft gasifier and used in multiple batch incubation experiments to evaluate equilibrium phosphorus concentration, maximum P sorption capacity (Smax), and adsorption/desorption potential. Both, RH (12.6 g kg-1) and HB (11.5 g kg-1) contained 10-15 times higher total P concentration than PF and BG, rendering RH and HB as potentially suitable products to be used as soil amendments. However, this initial P content of the agrichar seemed to have an overriding effect on the P sorption behavior of the agrichar. PF had Smax of 676 (±127) mg kg-1 for the non-sonicated agrichar, and 237 (±91) mg kg-1 following sonication. There was significant increase in CEC for PF and BG agrichar upon sonication. PF agrichar increased from 27 (±3) cmolc kg-1 to 41 (±4) cmolc kg-1 with sonication. Similarly, BG agrichar CEC increased from 21 (±2) cmolc kg-1 to 45 (±5) cmolc kg-1 with sonication. Initial total P and Ca concentration and their ratios was found to play significant roles on P adsorption and desorption. Major cations like Ca, Fe, Al and Mn are found to act as active sorption site for phosphorus controlling its fate and mobility along with compounding effects of other physicochemical parameters.

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