Fig. 3. Manure history and long-term tillage effects on Bray P1–extractable soil P levels at three depth increments (0–2, 2–5, and 5–15 cm) at Lancaster, Wisconsin, 2000. CP-, long-term (annually since 1993) chisel plow without a manure history, NT-, long-term no-till without a manure history; CP+, long-term chisel plow with a manure history (applied annually from 1993 to 1997); NT+, long-term no-till with a manure history. Standard error bars are provided for replicate soil test P values.