Optimizing Nutrient and Water Management for Organic Mixed Vegetable Production Systems

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Commodities

Practices

• Crop Production: cover crops, irrigation, nutrient cycling, nutrient management, organic fertilizers, water management
• Production Systems: organic agriculture
• Soil Management: green manures, nutrient mineralization, soil quality/health

Optimal nutrient and water management are critical to sustainable farming and its goals of maximizing yield, food quality and profitability while maintaining soil fertility and soil health and minimizing environmental impacts. Certified organic growers must rely on non-synthetic amendments (e.g., compost, manure) and nitrogen fixation from legumes to meet crop nutrient demand. However, relying on these fertility sources poses several challenges in terms of balancing inputs and outputs for different nutrients (e.g., nitrogen, phosphorus) and synchronizing nutrient release in sufficient quantity to satisfy crop demand. Resulting organic amendments inputs are typically high to meet crop nitrogen demand and build soil organic matter but can result in phosphorus over-fertilization. Increasing nitrogen inputs via nitrogen fixation can also increase soil fertility, but without proper synchronization of nutrient release, nitrogen transfer to subsequent crops can be low (20-30%), which may increase losses via leaching, especially for sandy soils. Water management will also affect nutrient cycling, with potential impacts on nutrient inputs, yields, crop nutrient uptake, nutrient-use efficiency, and ultimately losses to the environment. Conversely, nutrient and water management affect weed and plant-parasitic nematode abundance, affecting the overall benefits of different nutrient and water management approaches. Ultimately, potential synergies and trade-offs among different nutrient and water management approaches will be site-specific and driven by practical considerations and constraints, affecting economic returns and the likelihood of grower adoption.

The proposed research will combine on-farm trials and a trial on a research station to better understand the linkages between nutrient and water management in organic mixed vegetable production systems in Florida. The ultimate goal is to determine how nutrient and water management can be improved in these systems. Our first objective is to evaluate current nutrient and water management practices of three farms to compute nutrient and water budgets and identify how nutrient and water management can be improved in these systems. In collaboration with these growers, we will develop on-farm field experiments to evaluate the effects of changes in management practices, such as using rainfed cover crop polycultures, different processed organic fertilizers, and/or sensor-controlled irrigation systems. Growers will also provide input as we design the replicated four-system experiment that will compare different nutrient and water management approaches at a research station site, which has similar soil and climatic conditions as participating farms. Finally, we will quantify economic costs and returns for all systems under study to determine their economic viability.

Both sets of experiments will be conducted for two years, focusing on crop productivity, nutrient cycling and soil fertility, soil health, water use, weed and nematode abundance, and economic costs and returns. Research results will be shared with individual growers to identify the most beneficial practices for their operation. We will develop extension materials and hold field days to share our results with the broader farming community. Ultimately, this project will identify how organic vegetable production in Florida and the Southeastern US can become more sustainable by identifying the most beneficial and profitable nutrient and water management approaches.

Objective 1: Build nutrient and water budgets with grower participation, using ancillary data and limited sampling, to identify leverage points to improve on-farm nutrient and water management;

Objective 2: Conduct on-farm trials to determine how different systems aimed at improving nutrient and water management affect yields, soil fertility and soil health, water application, and the abundance of weeds and plant-pathogenic nematodes;

Objective 3: Conduct a parallel trial in controlled conditions at PSREU comparing how different systems developed with grower participation affect the impact of nutrient and water management on the same indicators as objective 2;

Objective 4: Compare the economic costs and returns of alternative nutrient and water management strategies;

Objective 5: Synthesize information and communicate key outcomes to cooperating growers, Extension agents and the farming community via field days, Extension documents, and professional development workshops.