This is a study the influence of soil carbon amendments, as part of linked laboratory experiments and field operations, for the cycling of nitrogen compounds during managed aquifer recharge (MAR). The MAR field site is in Watsonville, CA, and collects and infiltrates stormwater runoff on a working ranch. Various soil carbon amendments were applied as permeable reactive barriers (PRBs), including wood chips and almond shells, two carbon sources previously known to enhance microbially mediated denitrification. Intact soil cores were recovered from an infiltration basin and used in flow-through experiments to replicate and extend field observations to quantify substrate controls on biogeochemical processes. For laboratory experiments, PRBs included mixtures of carbon sources and native soil at specific ratios (wood chips 1:1; almond shells 1:1, 1:3, and 1:10). Almond shells mixed with soil as 50% and 25% by volume removed the most nitrate in the laboratory experiments. These two treatments also produced higher amounts of manganese and iron. Elevated levels of these trace metals are interpreted as an indication of a more reducing condition where denitrification can occur more favorably. Wood chips removed a modest amount of nitrate, but also produced nitrite, indicating incomplete denitrification. In field operations, wood chips removed more nitrate than almond shells but also produced more nitrite. Based on isotopic results, nitrite oxidation may be occurring in the wood chip treated areas. We conclude that, overall, almond shells, at a high enough amount, are a better soil amendment than wood chips for removing nitrate during infiltration for MAR.

During the 1985 and 1990 Farm Bill debates, a movement emerged that sought to incorporate the goals of sustainable agriculture into legislation. As a consequence of this coalition-building process, important new policy initiatives were introduced. Recent efforts have also been made to link urban food concerns with sustainable agriculture agendas under the broader framework of food security advocacy. In relation to that effort, this paper lays out the framework and specific policy components of a food security approach, including the design of a "Community Food Security Empowerment Act" which identifies the connections between the sustainable agriculture and urban food agendas.

Natural groundwater recharge is inherently difficult to quantify and predict, largely because it comprises a series of processes that are spatially distributed and temporally variable. Infiltration ponds used for managed aquifer recharge (MAR) provide an opportunity to quantify recharge processes across multiple scales under semicontrolled conditions. We instrumented a 3-ha MAR infiltration pond to measure and compare infiltration patterns determined using whole-pond and point-specific methods. Whole-pond infiltration was determined by closing a transient water budget (accounting for inputs, outputs, and changes in storage), whereas point-specific infiltration rates were determined using heat as a tracer and time series analysis at eight locations in the base of the pond. Whole-pond infiltration, normalized for wetted area, rose rapidly to more than 1.0 m/d at the start of MAR operations (increasing as pond stage rose), was sustained at high rates for the next 40 d, and then decreased to less than 0.1 m/d by the end of the recharge season. Point-specific infiltration rates indicated high spatial and temporal variability, with the mean of measured values generally being lower than rates indicated by whole-pond calculations. Colocated measurements of head gradients within saturated soils below the pond were combined with infiltration rates to calculate soil hydraulic conductivity. Observations indicate a brief period of increasing saturated hydraulic conductivity, followed by a decrease of one to two orders of magnitude during the next 50 to 75 d. Locations indicating the most rapid infiltration shifted laterally during MAR operation, and we suggest that infiltration may function as a "variable source area" processes, conceptually similar to catchment runoff.