Under the Cover of Green Manure

We’re all familiar with that wonderful brown substance we call manure, or, as I prefer to call it, “fruit of the butt.” Manure is a rich source of nitrogen for our growing plants, and it can also serve as a mulch. Yes, without manure, life would be pretty sh…, well, you get the idea.

Now, I’d like to introduce you to a different kind of manure. This kind does not come from a bovine or equine backside, but it grows right out of the soil. These are various plants known collectively as cover crops or green manure. Green manure plants are grown for the sole purpose of being killed by cold weather, chopped up, and worked into the soil. Like the other kind of manure, it provides nitrogen, but it does a whole lot more. Green manure crops can crowd out weeds, reduce soil erosion, and improve the overall condition of the soil.

Green manure crops are generally planted in late summer or early fall, then chopped up and worked into the soil in the early spring. Alternatively, they can also be planted in spring or summer, and then tilled into the soil before planting a vegetable crop. They can also be planted in place of a vegetable crop and then worked into the soil to condition it for the following year’s crops.

Green manure crops consist of both legume and non-legume plants. Legumes such as field peas or vetch are planted for their nitrogen-fixing ability while non-legumes – grain crops like rye or wheat are planted for their ability to crowd out weeds. A wide variety of plants can be used as green manure crops. The table below lists some common ones.

The University of Wisconsin Horticulture, Division of Extension gives these instructions for planting. To plant a cover crop or green manure, first clear the planting area of any large stones and other debris.  Rake the area smooth and broadcast seed according to the seeding rate given in Table 1 or as recommended by the seed provider.  Rake the area again to incorporate the seeds into the soil, and lightly water the area. To prevent the cover crop from self-seeding in other areas of your garden, and to utilize the cover crop to its fullest potential, cut down plants when, or just before, they start to flower.  You can cut plants by hand, or by using a trimmer, brush cutter, or mower.  Cutting before flowering not only prevents the cover crop from going to seed, but also stops the plant from taking up nutrients from the soil to store in its seed.  Once plants have been cut, incorporate the plants into the soil (using a shovel, pitch fork or rototiller) where they can more readily decompose.  Allow approximately two to three weeks for the cover crop to decompose before planting your vegetables into the soil. (Source: University of Wisconsin Horticulture, Division of Extension)

So if you are looking for a way to improve the condition of your soil, and the brown manure isn’t doing the job, then why not try the green?

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Too Much of a Good Thing

Our vegetable crops require the absorption of specific elements in order to survive and thrive. However, our garden soil may be lacking in one or more of these nutrients. That is the reason why we apply fertilizer to our gardens. A fertilizer, by definition, is a substance that improves plant growth directly by providing one or more necessary plant nutrients.

When applying fertilizer, take care to apply the correct amount. More is not better. In fact, overfeeding can do more harm than good.

Applying too much nitrogen (usually in the form of manure) will cause the plants to produce an overabundance of leaves and a dearth of flowers and fruit. Plants need phosphorous to produce flowers and fruit. That’s why, if you use manure in your garden, you should also provide supplemental phosphorous.

Many fertilizers are also salts. Overfeeding of fertilizers can cause a build-up of salt in the soil. According to Texas A&M’s AgriLife Extension Service, when the soil absorbs too much salt, it eventually loses the ability to absorb water. In addition, overfeeding can cause an over accumulation of boron and chloride, which can result in slowed or stopped plant growth, yellowing foliage and even the death of the plants.

So how do you avoid overfeeding? Probably the best way is to test your soil before applying anything. You can purchase soil test kits from local nurseries or from gardening catalogs. You can also send samples of your garden soil into a lab for testing. The results of the test will show what nutrients are deficient, optimum, and in excess. This will establish a baseline that will guide you in choosing the right fertilizers and applying the right amounts to insure that your plants get all the nutrients they need – not too much and not too little.

The Pervasive Power of Poop

Poop, by the strictest definition, is the waste product left over from the digestion of a food source. Call it what you will — scat, number 2, muck, feces, manure, etc. Sure, it can be gross and disgusting, especially when it’s fresh. But our lives would be so much poorer without it, although for some people, their lives are poorer with it, in which case, may I suggest a laxative? But I digress.

 
As gardeners, we all know how important manure is as a relatively inexpensive source of nitrogen, a critical nutrient, for our garden vegetables. For many of us, if it wasn’t for this “fruit of the cow’s butt” (or horse’s butt or bat’s butt), the fruit of our gardens would be considerably reduced. Ever heard of castings? Castings are another excellent source of critical garden nutrients. They’re also a fancy name for worm poop.

When we make cheese, we add a starter culture to our milk. The bacteria in this starter culture will chew up the sugar (lactose) in the milk and convert it to lactic acid. This lowers the pH of the milk and prepares it for coagulation. So you can think of this lactic acid as bacterial poop.

 
When fungi colonize a growing medium, they secrete enzymes to break down the food source. They then absorb the nutrients through their cell walls and excrete waste products. They literally swim through their own fungal poop. Then, when the temperature, humidity, and light are just right, the fungi will produce their fruiting bodies, a.k.a. mushrooms. Then we eat the mushrooms — that came from the fungi that was swimming in its own poop. And speaking of mushrooms and poop, do you like portabella mushrooms? You do? Excellent, because they are grown in a pasteurized substrate which often contains horse manure as one of the ingredients.

 
And last, but not least, how in the world would political campaigns ever even get off the ground without manure to propel them forward?

 
So remember folks, love may make the world go ’round, but poop is the grease that keeps all the gears moving!