Fig. 4. Levels of E. coli in cornland plot runoff by treatment factors and interactions. Error bars represent ±1 standard deviation; bars labeled with different letter(s) differ significantly (P 0.1). In (C), treatment codes 0, 30, and 90 indicate age of applied manure in days; codes 1 and 3 indicate delay between manure application and simulated rainfall in days. In (D), treatment codes I and N indicate manure incorporated or not incorporated; codes 1 and 3 indicate delay between manure application and simulated rainfall in days.