Can the presidedress soil N test help predict in-season fertilizer needs after fall-applied manure?
Study author(s): Melissa Wilson, University of Minnesota
Growing season(s): 2022, 2023, 2024, 2025, 2026, 2027
Minnesota location: Waseca
Note: Please download reports below.
WHAT IS THIS PROJECT ABOUT?
This project tests whether the pre-sidedress soil nitrate test (PSNT) can reliably predict extra in-season nitrogen needs for corn fields that received fall-applied manure. Manure provides valuable nutrients, but predicting exact nitrogen availability by late spring is challenging. This study aims to help farmers avoid over-applying commercial fertilizer or under-nourishing their crop by evaluating how spring nitrogen sources compare under different crop rotations.
WHAR ARE KEY PROJECT GOALS & POTENTIAL FARMER BENEFITS?
- Predict In-Season Nitrogen: Determine if the PSNT helps optimize sidedress fertilizer rates after applying fall manure.
- Protect Yields & Lower Costs: Help growers make accurate, cost-effective fertilizer decisions without risking yield losses.
- Evaluate Nutrient Sources: Compare performance between dairy manure, swine manure, and synthetic spring fertilizer across continuous corn and corn-soybean rotations.
HOW WILL THE STUDY BE CONDUCTED?
- Multi-Year Field Trials: Researchers conducted multi-year field trials comparing yield outcomes across continuous corn and corn-soybean crop rotations.
- Treatment Comparisons: Each trial evaluates crop performance under zero added nitrogen, dairy manure, swine manure, and synthetic spring fertilizer at varying sidedress nitrogen rates. All pre-plant application rates were 120 lbs N/acre and the sidedress rates ranged from 0 N to 1.2x the recommended rate, depending on the crop rotation.
- Data & Weather Analysis: Researchers are combining data across all field seasons to perform statistical analyses and evaluate how spring weather conditions impact nitrogen availability and yield performance.