📊 Soil Analysis

Averages yield across all years at each location. A sample with 180 bu in 2024 and 220 bu in 2025 becomes 200 bu.
Best for: Finding patterns that persist across years. Smooths out weather variation.

Each year treated as separate data point. Same location counted multiple times (once per year).
Best for: Maximum sample size when years had similar growing conditions.
⚠️ Combines good and bad years together - results may be misleading if yields varied significantly.

Each year treated separately, but yields converted to % of that year's average.
Example: 200 bu yield in a 180 bu avg year = 111%. 250 bu yield in a 250 bu avg year = 100%.
Best for: Comparing across years with different weather. Isolates nutrient effect from seasonal variation.

Only uses yield from that specific harvest year.
Best for: Analyzing a specific season's results.

Correlations include differences between fields. A high-yielding field with high P will inflate the P-yield correlation, even if P isn't the reason that field yields well (could be better soil type, drainage, etc.)

Yields are converted to "% of field average", removing field-to-field differences. This isolates the nutrient effect by asking: "Within each field, do higher nutrient levels produce above-average yields?"