Fig. 1. Manure history effect on Bray P1–extractable soil P levels at three depth increments (0–2, 2–5, and 5–15 cm) in a long-term chisel plow system at Madison, Wisconsin, 2001. None, no manure; 1995 & 1998 and 1996 & 1999, manure applied only in these two years; 1994 to 1999, manure applied annually for six years during this period. Standard error bars are provided for replicate soil test P values.