ASHS 2025 Conference

Organic farming systems face inherent limitations in nutrient management, particularly when plant nutrient demand exceeds available supply. This multi-year study examined the effectiveness of various soil amendment strategies and cover cropping systems on soil health indicators and pepper yields across three Purdue Agriculture Research Centers in Indiana (Wanatah, Lafayette, and Vincennes). Our experimental design compared conventional, organic, and mixed soil amendment approaches using standardized nutrient targets across treatments. Soil amendments included conventional and organic nutrient sources, plant and manure-based, or mixed (leaf mold and manure) compost applications. Summer cover crops (mustard for biofumigation, sunn hemp for nitrogen fixation, and sorghum-sudangrass for biomass production) were planted in Year 1, while a mix of cereal rye and hairy vetch served as fall/winter cover crops throughout the study. Buckwheat was seeded in bed row middles during Years 3 and 4. Soil health was assessed using the Haney test on composite samples from fifteen 15 cm deep soil cores per experimental unit. Initial challenges from nutrient losses due to heavy rainfall and significant weed pressure in 2021 necessitated management adaptations, including preplant herbicide application and plastic mulch protection of soil amendments. Soil health metrics improved dramatically at the Lafayette location in 2022 (67-202% increase) but showed minimal improvement at Wanatah and Vincennes. By 2023, average soil health declined by 14% across sites, primarily due to decreased water-extractable organic nitrogen (WEON) and slight reductions in water-extractable organic carbon (WEOC), resulting in reduced microbial activity. Our findings demonstrate that summer cover crops combined with fall/winter cover crops produced comparable benefits to high-rate compost applications for both crop yield and soil health improvements. However, high compost applications, particularly at Lafayette, led to extremely high P₂O₅ levels that required adjustment of fertility management. Soil respiration emerged as a reliable predictor of overall soil health, with statistical analysis indicating that a 10-point increase in soil respiration corresponded to soil health improvements of 1.0, 1.1, and 1.3 units at Wanatah, Lafayette, and Vincennes, respectively. This research provides evidence-based guidance for integrated soil fertility management that balances immediate crop nutrient needs with long-term soil health objectives, offering sustainable strategies for both organic and conventional production systems.