Corn and Soybean Growth as Affected by Wastewater-Derived Struvite-Phosphorus Sources and Irrigation Water Types

Struvite (MgNH4PO4·6H2O) produced synthetically from a stock solution of known phosphorus (P) and nitrogen (N) concentrations has been shown to be an effective, alternative fertilizer-P source for various crops, but little is known about the potential agronomic effectiveness of struvite created from an actual municipal wastewater source. The objective of this study was to evaluate the effects of soil [i.e., Creldon silt loam (Oxyaquic Fragiudalf) and Calloway silt loam (Aquic Fraglossudalf) series], fertilizer-P source [i.e., synthetically produced electrochemically precipitated struvite (ECSTsyn), real-wastewater-derived ECST (ECSTreal), chemically precipitated struvite (CPST), monoammonium phosphate (MAP), and an unamended control (UC)], and irrigation water type (i.e., tapwater and struvite-removed wastewater) on corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] growth and N, P, and magnesium (Mg) uptake in a 60-day, greenhouse potted-plant study. Crop growth and N, P, and Mg uptakes for the struvite treatments (i.e., CPST, ECSTsyn, and ECSTreal) were generally similar to or at least 1.2 times greater than MAP. The ECSTsyn material commonly had up to five times greater N, P, and Mg uptake in corn and soybean than any other fertilizer-P source. Struvite-removed wastewater resulted in at least 1.3 times lower dry matter and N, P, and Mg uptake than tapwater. Similar corn and soybean results from the struvite fertilizers among the various soil-water type combinations compared to MAP suggest that struvite generates similar crop responses as at least one widely used, commercially available, multi-nutrient fertilizer-P source.

Runoff-Water Properties from Various Soils as Affected by Struvite-Phosphorus Source and Water Type

Struvite (MgNH4PO4?6H2O) can be produced from municipal wastewater and has been shown to be an alternative fertilizer-phosphorus (P) source for various crops, but little is known about the runoff-water-quality implications from soil-applied struvite. The objective of this study was to evaluate the effects of soil [Creldon (Oxyaquic Fragiudalfs), Dapue (Fluventic Hapludolls), Roxana (Typic Udifluvents), and Calloway (Aquic Fraglossudalfs) series], fertilizer-P source [synthetically produced electrochemically precipitated struvite (ECSTsyn), real-wastewater-derived ECST (ECSTreal), chemically precipitated struvite (CPST), and monoammonium phosphate (MAP)], and water source (rainwater, groundwater, and struvite-removed real wastewater) over time on runoff-water-quality parameters from laboratory-conducted, rainfall-runoff simulations. Mesh tea bags containing each soil-fertilizer treatment combination were rained on with each water source (Trial 1), incubated for 6 months, and rained on again (Trial 2) to evaluate runoff-water quality. Struvite fertilizers had similar runoff-water-quality properties to those from MAP. In Trial 1, runoff total P (TP) concentration differences (i.e., soil-fertilizer-water-type response minus control response minus blank response) from ECSTsyn or ECSTreal were 1 to 5 times larger than MAP and CPST for all water-soil-fertilizer-P source treatment combinations, except for the Creldon-groundwater and Roxana-wastewater combinations. In both trials, runoff TP decreased over time in all water-soil and soil-fertilizer-P source treatment combinations, except for the Roxana-CPST combination where TP increased over time by 46%. The similar water-quality responses from the struvite fertilizers among the various soils and water types compared to MAP suggest that struvite has similar runoff-water-quality implications as at least one widely used, commercially available fertilizer-P source.

A Stakeholder-Guided Collaborative Approach to Improve Water Quality in a Nutrient Surplus Watershed

The need for water quality improvement in nutrient surplus watersheds is a pressing issue on the agenda of some government agencies and environmental organizations. Including the water quality perceptions of different affected stakeholder groups in the decision-making process may help in addressing this issue. Unfortunately, there is a lack of published research focusing specifically on understanding how Arkansas stakeholders’ perceptions of water quality issues can be used to build and implement comprehensive and workable water quality management plans. Therefore, the objective of this study was to use a stakeholder-guided collaborative approach to help research and outreach personnel to understand water quality perceptions of key stakeholders and to integrate stakeholder engagement in both the decision-making process and in the implementation of water quality management strategies within the Lincoln Lake Watershed in northwest Arkansas. Two key stakeholder groups (i.e., Locals—residents and agricultural producers—and Outsiders—water quality specialist across the state) were surveyed to assess their perceptions regarding: 1) causes of watershed water quality problems, 2) parties responsible for water quality improvement, 3) effectiveness and affordability of best management practices to reduce water quality degradation, and 4) the stakeholders’ interactions with county, state and federal government. A total of 209 complete surveys (49% response rate) were received. Survey responses were compared to determine if significant differences existed between the two stakeholder groups’ perceptions of water quality performing Fisher’s exact tests. Results from the study showed that water quality is still perceived as an issue in the Lincoln Lake Watershed. Significant differences were found between the two stakeholder groups’ perceptions regarding: 1) different groups’ contributions to water degradation, 2) groups’ responsibilities for cleanup, 3) effectiveness of five best management practices, 4) affordability of four best management practices, and 5) what level of government (i.e., county, state, federal) best represents Locals’ water quality needs and concerns. The lessons learned from this collaborative approach helped identifying Locals’ important knowledge gaps regarding water quality and best management practices effectiveness. Consequently, awareness and education campaigns in conjunction with a stewardship recognition program were conducted to encourage appropriate water conservation strategies within the Lincoln Lake watershed and its adjacent areas.