The Soil-Crop Connection: Linking Functional-Food Potential of Leafy Vegetable Crops to Organic Soil Amendments

Commodities

• Vegetables: greens (leafy), greens (lettuces)

Practices

• Crop Production: food product quality/safety, organic fertilizers
• Education and Training: farmer to farmer

Sustainable, organic and regenerative agricultural approaches support the long-term microbial and structural health of soils to grow nutritious crops. The factors that modulate plant nutrient uptake, and hence plant nutritional quality for consumers, include diverse beneficial soil microbes, environmental conditions and plant genetics. Production of nutrient dense crops not only supports farmers' economic viability, but also enriches consumer diets with micronutrients, a healthy microbiome and plant bioactive compounds, the latter serving as important extra-nutritional constituents that confer antioxidant, anti-inflammatory, immuno-modulatory and anticancer properties. Despite this knowledge, the direct connection between soil management practices and crop (extra-)nutritional quality remains understudied - data on bioactive phytochemicals are especially lacking. This limits farmers' ability to make science-backed nutritional claims about their sustainably cultivated crops, hence possibly missing marketing opportunities. Since the microbial diversity of soil may be enhanced by addition of rich organic amendments, and beneficial microbes modulate plant phytochemicals, our study will investigate how the application of different organic fertilizer regimes link to leafy vegetable crop nutritional quality outcomes and functional-food potential. We will collaborate with our farmer partner ECO City Farms, a compost and vegetable producer in Maryland, to conduct field trials at a University of Maryland research farm. Experimental trials will assess how compost, vermicast and compost extract from ECO City Farms affect leafy greens. Following cultivation and harvest of leafy crops under field (high tunnel) conditions, we will profile and estimate concentrations of plant bioactive phytochemicals - phenolics, flavonoids, carotenoids and glucosinolates, using rapid methods developed by our team. Data will be shared via infographics and presentations, online and at field events hosted by ECO City Farms. The project findings will point to efficacious organic soil amendment practices that boost crop quality, providing science-backed knowledge and tools to farmers which could be used in decision-making related to soil management for optimized crop nutritional and functional-food quality.

Our overarching goal is to decipher the soil-microbe-crop nutrition connection, especially in relation to functional-food potential. Despite growing commitment to sustaining soil health, crop health-promoting nutritional outcomes in relation to such practices remain poorly understood. The goal of this project, therefore, is to evaluate how organic soil amendments affect leafy crop (extra)-nutritional quality, with a focus on bioactive phytocompounds. Data from this project are expected to substantiate our long-term aim to relate pre-harvest practices with enhanced product quality outcomes, which in the future could serve as scientific basis for seeking approval for marketing claims, hence also supporting economic viability.

Amendments will include compost from locally sourced green waste, vermicompost and compost extract, produced at ECO City Farms, our Farm Partner in Maryland. Experimental trials will be conducted in a high tunnel at UMD's Upper Marlboro Facility, using greens frequently grown at ECO (kale, chard or lettuce).

We will evaluate soil activity, crop growth and (extra)-nutritional quality of two leafy vegetables in response to three combinations of organic soil amendments or NPK controls.

Objective 1: Organic amendments and soil activity

Specific Aim 1a: Conduct nutrient analysis of organic fertilizers, compost, vermicast and compost extract.

Specific Aim 1b: Evaluate microbial activity of soil in leafy crop plots amended with organic fertilizers or NPK.

Objective 2: Crop nutritional quality and functional-food potential

Specific Aim 2a: Measure fresh weight, chlorophyll and micronutrient content of leafy crops.

Specific Aim 2b: Measure phenolics, flavonoids, carotenoids and glucosinolates (bioactive phytocompounds) in leafy crops.

Objective 3: Outreach and educational activities

Specific Aim 3a: Create infographics on organic amendments, application and crop quality outcomes.

Specific Aim 3b: Organize Farmer Partner led field events at ECO City Farms to educate beginner and small-scale farmers on the soil-microbe-crop nexus, composting techniques, and to share research findings on crop nutritional quality.