MONTPELIER, Vt. (AP) -- Vermont's Agency of Agriculture, Food, and Markets has started its annual ban on winter manure spreading as part of a strategy to protect water quality.

Manure spreading is a common practice in Vermont agriculture, which enriches the soil for production. Vermont's annual ban, which went into effect Saturday, has been used since 1995 under the Accepted Agricultural Practice rules.

Officials say research has shown that manure applications on frozen ground can increase the runoff potential.

The ban is in effect until April 1. This year, however, the ban was lifted early, due to unusually dry conditions in Vermont, a result of the warm winter.

Copyright 2012 The AP.