Question from Robin:
Thank you so much for the informative and entertaining lecture last night! It was a pleasure to meet you finally in person – I gave you my card – Harmony Organic Gardens.  and said that I would send you information about the compost/amendment source I had asked you about – I don’t know if you’ve had any experience with them, but my soil science instructor at Mira Costa College – Meghan Farleigh – really likes Mary Matava’s products, so I am going to try some soon. Here is the link:

http://www.agriserviceinc.com/index.html

Meghan also swears by alfalfa for mulch and I think I heard you say you didn’t recommend this. Can you explain?

Answer from Pat:
Robin: Thank you for attending and enjoying the talk and for the information on top soil. People often ask for good sources. I am intrigued in what you told me about using alfalfa for mulch and want to hear more about it. First to define the term “mulch”:  Mulch is an organic or inorganic material placed on top of the ground to help maintain moisture in the ground and cut down on weeds. Organic mulches gradually break down and eventually when thoroughly rotted improve the soil. Inorganic mulches such as black or red plastic can be used to heat up the soil and the air in cool coastal climates and increase yields of certain crops such as melons. Organic soil amendments and aged compost are different. These are well-enough rotted to be combined with the soil without subtracting nitrogen from the soil in order to rot. Alfalfa is in this category since it is a legume and thus has a high nitrogen content. For example, alfalfa can be grown from seeds planted in spring as a warm-season cover crop and dug directly into the ground in fall to improve the soil.

Because of its high nitrogen content I am sure that alfalfa used as mulch would quickly break down and then could be incorporated into garden soil, but some might dry out on top of the ground thus allowing some of the valuable nitrogen contained in it to escape into the air. (This can happen with any fertilizer left on top of the ground and not watered or cultivated into the ground.) Baled alfalfa seems like an expensive material for mulch when much cheaper or even free organic materials make excellent mulch. Baled alfalfa is a commonly used food for horses and other domestic hoofed animals. Moldy alfalfa hay, however, would make horses sick if fed to them, so it can often be obtained free if one can find a source.  Ground alfalfa meal or alfalfa pellets are used as rabbit food and also as an organic nitrogen fertilizer which one can work directly into the soil. (For more details, see my book and the chart on generic fertilizers on this website.)

Another reason one would not normally think of alfalfa as a mulch is because it is a legume. Leguminous plant materials, such as bean straw and green alfalfa, can be dug straight into the ground since they contain enough nitrogen to rot quickly in the ground. Alternatively one can layer alfalfa with a manure, such as clean horse manure as I suggested last night to make a very nutritious compost and do so amazingly quickly, within a month or two, without tossing and turning. (See the detailed explanation on pages 35 and 36 of my organic book.)  Another reason that I would be a little hesitant to use alfalfa hay as mulch is that alfalfa left lying on top of the ground near stables, for example, has the tendency to attract rats, opossums, racoons, very hungry coyotes, rabbits, and other animals who like to eat it. (Dogs and cats, however, can keep pest animals away.)

I would like to know more about why Meghan likes using alfalfa as mulch and what her experiences are. Perhaps there are no animal pests where she gardens or perhaps there are other factors involved that I’m not taking into account.

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