Farmers, environmentalists and pollution cops are unhappy with the system for policing pollution caused by farm irrigation that went into effect a year ago. And almost no one can point to evidence that the new system of testing by coalitions of farmland owners is doing any good. The first reports that might show whether the coalitions have managed to prevent toxic substances such as pesticides from running into rivers or sinking into groundwater are due April 1. But two of the nine coalitions that cover the Central Valley -- including the one handling farms in San Joaquin County and the...