An investigation on effect of season on weed seed viability during composting process

Adding fresh manure to cropland result in an increased weed population from seed present in the manure. Composting process can destroy weed seed viability. High temperature is an important factor in decreasing of seed viability. In an experiment the effect of season on seed viability of sixteen important weed species in forage fields were investigated during composting process. Seeds enclosed within nylon mesh bags were buried into the compost pile، at 0. 5، 1 and 1. 5 meters depths from surface for 4 months in the early of summer، autumn and winter in 2004. The compost pile made from cow manure. Seed packets were removed monthly to test for seed viability. The results showed that the temperature pile increased in three season and it was more than environment temperature. Temperature pile in summer was more than two other seasons. The most of weed seed viability loss observed in summer. Compost pile tended to have hotter temperatures at 0. 5 meter than deeper layer. Weed seeds lost their viability at the 0. 5 m depth where had the most temperature in comparison to deeper depths in all of seasons. The mean of weed seed viability loss after four months in summer، autumn and winter were 97. 03، 83. 80، 24. 71 at the 0. 5 m depth and 73. 58، 60. 71، 17. 15 at all the layers، respectively.