Dear Community Gardeners,
We will have three types of mulch/compost available this growing season.
1) The wood chips are for the pathways, both to give the gardens a tidy appearance and to keep weed growth to a minimum. I would generally not use them to mulch directly around plants. The breakdown of the wood can rob the soil (and therefore your plants) of needed nitrogen. The wood chips will be available as needed throughout the growing season.
2) The leaf mulch (made from town residents’ leaves and chopped at the Transfer Station – provided for our use by the Branford Parks and Recreation Department) is good both to mix into the soil before planting (improves humus content) and used as a surface mulch (1″-2″ around the base of plants). Later in the spring we’ll strongly encourage surface mulching to help the soil retain moisture throughout the growing season. Helping the soil retain moisture will both be better for your plants (they need the moisture), you (you won’t need to water or weed as often) and the BCG water bill (our financial resources are limited). Surface mulching will become important as the soil warms and we move into mid-late May. Right now some of the gardens are so wet that we want to encourage soil drying instead. The leaf mulch will be available throughout the growing season.
3) The source for the horse manure is from a friend of Steve DuHamel’s (V.P. of BGC). The friend has the contract to remove the horse manure from the Yale University stables. He mixes it with loam and leaf mold, then it composts for 6-8 months. I had several questions about composted horse manure (I grew up on a dairy farm, so am more familiar with cow manure), so I contacted Bill Duesing, Executive Director of CT Northeast Organic Farming Association (aka. CT NOFA). Specifically the questions were about potential contamination of horse manure with any medicines that horses are given or from something they eat, and also the proper usage of composted manure to avoid soil borne illness (eg. from E. coli bacteria). His response (in part) follows:
“I know that many farmers, including certified organic ones, use horse manure as part of their fertility program. It is my understanding that the many, many different organisms in the composting process are able to take apart most of the pesticides involved. The national organic standards do not require compost ingredients (or mulches) to be from organic sources. You can find the standards at baystateorganic.org.
UDSA organic standards require that any animal manure used in organic production either be composted according to strict guidelines, with careful monitoring of temperature, turning and thorough recordkeeping OR be applied three months before the harvest of an above ground crop (corn for example) or four months before the harvest of a ground contact crop – potatoes, carrots, non-staked tomatoes, for example). This is to avoid food safety issues with the manure. Many organic growers will add manures (or not officially composted manures) in the fall so there is plenty of time to meet that standard.
We should all be aware of phosphorus levels. If a soil test reports very high or above optimum levels of phosphorus, no more phosphorus should be applied. The leaves are not very high in phosphorus, but manures are. A soil test is always good before adding nutrients.”
OK, so the take home message is that the composting process generally takes care of any unwanted substances in compost and that certified organic farmers use manures, even if they come from non-organic sources. But, has our horse manure been composted by strict USDA standards? Probably not. So, what I would like to suggest is if you want to add the horse manure compost, do it as soon as you can (but avoid working with super soggy soil). Spread 1″-2″ of the horse manure compost over your soil, then turn the soil under.
Manure composts are a wonderful source of fertilizer and will improve the humus content of your soil. Farmers have safely used manure composts for thousands of years! The problem can be if E. coli contaminated “raw” manure comes in contact with vegetables that aren’t cooked. Time and composting take care of potential contamination problems. So, it’s a good idea to either mix manures into the ground early in the spring (allowing for a few months before harvest of any food), and then again in the fall (allowing the composting process to continue over the winter). I will add the horse manure this spring; we’ve already put some of the horse manure compost into one of the Seed, Weed and Feed plots. I will not be adding horse manure compost throughout the growing season (just to be conservative in approach), but I will add leaf mulch throughout the growing season.
Bill Duesing also said that horse manures are generally not as much of a worry as pig or cow manures from feedlots, and that the USDA guidelines (4 months before harvesting foods that come in contact with soil, and 3 months for non-contact food) are likely pretty conservative. Our horse compost has already started on the composting process – it doesn’t smell like poop, doesn’t have large recognizable chunks of sawdust or wood chips and is uniform in texture, so is at least some steps away from being considered “raw” manure.
As for Bill’s comment about the phosphorus content, last spring our phosphorus content tested very low in the soils at BCG. I’m assuming (but I did send in soil samples for the two Seed, Weed and Feed beds for testing), that overall, the phosphorus content remains low in the soils, so this is likely not a concern for us yet.
We’ll probably have the horse manure compost available this spring to mix in before planting, then again in the fall to mix in before overwintering the garden.
Here’s the disclaimer: BCG will get the composts for you through our sources, as available. It’s up to you to decide if you want to use the composted leaf mulch or composted horse manure, or not. If you have any qualms about it – don’t use it.