True Confession: Since I began working (RE: paid employment) more (I always work, am very busy), I have had less time for the garden (insert frowny face here) and it is in need of some renovation and re-working. I hope to be posting on my progress with this. One thing I have written about already is moving towards a no-till garden, using the Ruth Stout method of piling high the natural mulches and planting into them. In areas when I have done this, I have far fewer weeds and it is a lot less work (there are disadvantages, like cover for voles, but more on that another time). I wanted to expand this method throughout the food gardens, by collecting leaves and pine straw. I also want to investigate the availability of municipal compost and less costly sources for straw. But are these two latter ideas good ones?
Both straw and municipal compost can be contaminated by herbicides (I have written on this before too). It used to be that the composting process broke down herbicides into less harmful compounds, but a new class of herbicides (including picloram, clopyralid, aminopyralid-based compounds: Confront, Forefront...), found in both straw and compost, can persist for a way longer time than prior herbicides, and are called "garden killers" for their long-lasting and devastating effects on gardens. If you unknowingly use products contaminated with these herbicides, your garden will no longer be organic and you might not be able to get much to grow, for many seasons.
These herbicides might be on the grass that is composted in municipal sites, sprayed on the hay/straw as it grows to prevent weeds and in the manure of animals that eat contaminated hay. If you cannot get tested products (and you probably cannot) you can do your own home test. For commercial or municipal compost, fill a dozen three or four inch pots, half of them with potting soil only and the other half with an equal mix of municipal compost and potting soil and mark the pots. Put three bean or peas seeds in each pot (these plants are more susceptible to this herbicide damage) and water them. Keep the pots separated, so drain water from the potentially contaminated compost does not contaminate the potting-soil only pots. When each plant has emerged and has three sets of leaves, compare them. If the plants in the compost mix have cupped leaves, or odd thickening or distorting of the leaves, contamination might be present.
But what do you do if you are testing compost you brought home and it is contaminated? First, buy only enough to test, so, if it is bad, you did not purchase much. But make sure that, in the case that the compost tests OK, you can buy more from the same pile you got your sample from (insure that new material is not mixed in). However, many municipal compost operations make their compost in long rows, mixing materials and piles together with a backhoe. This might mean that compost purchased on week and tested is not really the same compost that is available the next week. But, if you buy a lot, you may be stuck with a lot. If you buy a little, that might be all you can get. Overall, this might mean that fewer people (like me) will bother with municipal compost, unless is it tested at the source.
Straw is another matter altogether and harder to test. What I would try is to repeat the experiment above, using larger pots, with an inch of straw in the bottom, potting soil and an inch of straw on top. Compare this to plants in pots with no straw. Plant the seeds in the soil layer, water well and see what happens.
Other options? Make your own compost, and use gathered leaves and pine straw for mulch.