Saturday, April 10, 2010

CROP ROTATION - THE FOUR CROP METHOD

Back in the 1990's I was an average gardener trying to work out the basic issues, plot layout, which crops
to plant together, which crops to keep away from each other, what to feed my crops, what to do about
insect infestations.  Let's face it, I was confused.  Enlightenment came in the form of an article I read in a
gardening magazine (Organic Gardening?).  It was about the concept of crop rotation and its importance
to successful vegetable gardening.  This article changed my life.

As I recall, the author was a small scale commercial farmer.  She had worked out a simple, manageable
system that anyone could implement in their home garden.  The key to her approach was to organize
your crops into four basic groups: legumes, leaf crops, fruit crops, and root crops.  This works best if
you can divide your garden into fourths.  I've got 16 beds in my basic rotation and this works very well
for me.  An important thing to remember is to keep like vegetables together in the same bed.
At left is a typical leaf crop bed.  There are various lettuce varieties,
cabbage, broccoli and spinach in this bed.  The photo was taken in early
May in 2007.

Now that we have our garden layout organized around a four crop rotation
we can now consider soil amendments and nutrition.  One of the benefits of
legume crops is that they add nitrogen to the soil.  Leaf crops love nitrogen.
That's why leaf crops follow legumes.  It's genius!  At the end of the legume
season you can prepare this bed for all of the crops to follow by adding two
soil amendments; green sand and rock phosphate.  Rock phosphate is rich

in phosphorous a key element in growing healthy tomatoes, peppers and other fruit crops.  It takes a good
year to break down in the soil so that it can be used by the plants.  That's why you want to add it now.
Green sand has potassium which is needed for healthy root crops.  Green sand takes about two years to
break down in the soil, just in time for your root crop rotation.  In addition to these amendments, I plant
a green manure crop in the legume bed in the fall.  This will add more nitrogen to the soil and organic matter
when the crop is tilled into the soil in the spring.  In the spring I will add some compost to the soil before
I till.

One additional benefit to crop rotation is that moving your crops to a different bed every year confuses
the insects that prey on your vegetables.  It doesn't eliminate the problem entirely.  However, it does
help.  There will be more on garden insects in future posts.
All the best,
Greg

2 comments:

Chris W said...

Hi Greg,
I've been looking for a simple rotation schedule for quite a bit. Most are way too complex and vague at the same time, include too many variables, and are geared toward acres+ farms; not too suitable a backyard gardener. Anyway, the plan you write about has just made me say 'WOW" out loud. It is simple, straight forward, and makes sense.
Except for one thing...
In the body you write that after legumes leafs crops benefit from the N; but in the diagram you have roots following legumes, then fruit, then leaf crop. Also Following the legume crop you mention adding phosphate (which will take affect in a year) to benefit fruit, and greensand (taking effect in two years) to benefit roots. This has confused me, but it looks like the arrows on the diagram should be reversed. Making the rotation Legume > Leaf > Fruit > Root.
Does that sound right???
If not, then I am more confused than before :(.

Sent you an e-mail of the same content.

Thanks, (I hope)
Chris W.

Chris W said...

Greg,

Oh, and also, where would corn fit in, is considered a fruit? or a leaf (since it uses so much nitrogen & nutrients)? And I would like to follow my tomatoes with potatoes, but was told that they are related?? and share the same disease/pest issues. Is this right? then where do they fit in in the rotation?

Thanks again,
Chris