Fig. 1.

Export (normalized to site drainage area) of (a) total nitrogen (N) and (b) total phosphorus (P) from agricultural watersheds in the United States.

 


Fig. 2.

Percentage of agricultural area in (a) the Conservation Reserve Program and (b) conservation tillage in the United States in 2002.

 


Fig. 3.

Partial residuals and partial predicted export showing the relation between (a) total nitrogen (N) export and the area in conservation tillage and (b) total phosphorus (P) export and the area in the Conservation Reserve Program at different levels of soil erodibility.