Composting manure

 This blog was triggered by a Youtube item I saw in which the lass was covering her garden with cardboard and then wood chips in the fall to retard weeds in the following growing season.  A great idea and very effective.  It worked and her weeding was greatly reduced in the half of the garden she treated this way.  She showed how rich it made the soil, pointing out how black it was after this treatment.  She also mentioned that she spread composted manure before putting down the cardboard.  I put a comment on the bottom "Try raw manure in the fall instead of composted manure" but with no further explanation.  I thought I'd better justify the comment.  So why compost manure at all.

There are a couple of reasons to compost manure.  When an animal eats plants or animals, it poops out a portion of it's feces as mineralized chemicals.  That is to say, soluble mineral salts.  If the concentration of these salts are greater than the concentration of salts and sugars (solutes) in the root sap, water will be pulled out of the roots and cause what is called 'burning' of the plant.  Of course no burning occurs.  It is simply that the plant dries out and wilts, withers and looks burnt.  In addition, if it rains or if excessive watering is done, these soluble mineral compounds can be washed down beyond the root zone, making the unavailable to the crop and contaminating ground water and nearby water ways.

Think of chicken manure.  It is the 'hottest' of the manures.  That white material on the poop is uric acid which dissolves pretty completely in the soil water and makes a very concentrated solution.  If you ever use raw chicken manure, side dress with it so that it is incorporated, little by little into the soil.

What composting does, especially if the manure is bedding and therefore contains a quantity of saw dust or straw, is to let the microfauna in the manure use the bedding as an energy source and to take up the mineralized nutrients and build these nutrients into their bodies.  These are the primary producers in the soil.

We are all familiar with primary producers on land.  These are the plants that absorb sun energy and use it to build water, carbon dioxide and mineral compounds into proteins, carbohydrates and other high energy materials.

The soil also has primary producers but their source of energy is long chain molecules and especially the cellulose in wood chips, cardboard or straw.  Other wee beasties in the soil eat these primary producers and poop  mineralized compounds.  As long as there is enough cellulose in the soil, the primary producers will take them right back up and the cycle continues. 

As long as there is an excess of cellulose the plants will be starved of nutrients.  The soil primary producers are much better at grabbing the nutrients than the plants.  However as the cellulose runs out, some mineralized nutrients become available for the plants.  You have created a slow release fertilizer, ideal for growing plants.

You can see another reason to compost.  If there is lots of bedding, soon all the nutrients will be taken up and will not be available to the plants.  Either you 'burn' the plants with too much soluble material in the soil or starve them of nutrients because the primary producers in the soil are taking them all up.

However if the whole compost goes anaerobic or if even zones in the compost become anaerobic, two gasses are produced.  These are Ammonia NH₄ and Hydrogen sulphide H₂S.  The first takes away Nitrogen, the most  nutrient which is needed in the greatest quantities in plant growth and the second, Sulfur, a minor, but much needed nutrient,  These gases are what gives a compost pile the unpleasant smell and wastes nutrients that the plants could have used, come the spring.

It is very hard to keep a compost pile aerobic without constant stirring and who wants to spend their time turning over a compost pile. 

If, however you spread raw manure on the garden and especially if it is under a layer of cardboard and wood chips, It is almost impossible for it to go anaerobic in such a thin layer, and it has lots of cellulose material to use as an energy source for the primary producers.  It is much more likely that the nutrients will remain in the soil as the bodies of the wee beasties and be available to the plants as the growing season goes on.  You are not wasting these nutrients in a compost pile.

This is why I suggest using raw manure in the fall and best of all under a good layer of cellulose rich mulch.