Monday, 30 July 2012

crop rotation

One of the components of growing vegetables organically is planning your crop rotation. While I am not very good at and don't enjoy crossword puzzles, I do love figuring out each year's rotation plan. It is helpful to have various garden beds or, as I now have in the field, a big area that can be divided according to that year's plan.

The first thing to consider is the effect a crop can have on the bed and/or the soil. There are "cleaning" crops which are good for planting in the first year an area has been cleared. Potatoes are good for this because the process of hilling up throughout the season can keep the rows weeded on a regular basis. Also the fact that potatoes produce underground tubers can help to loosen the soil.
By the time the potatoes are just about to die down the foliage has almost extended to obscure the rows

Another crop good for cleaning a virgin bed is squash, both summer and winter. Since both squashes produce huge leaves and cover a big area, weeds tend to be shaded out as the season progresses. Of course, while this is the theory, weeds get a good start between the hills at the beginning of the season and if you don't keep pulling them out they can be pretty established by the time the squashes have really gotten going. Squashes are also heavy feeders so my squash hills are usually composed of nothing but manure and compost with a sprinkling of soil on top of the seeds. That manure and compost helps enrich the soil too.
The huge leaves of a fruiting zucchini plant mid summer.
The winter squash leaves are a little smaller than those of zucchini but they can send out shoots up to 10 feet from the roots. Unfortunately you can also see the prolific weeds between the hills.

Once the ground has been cleared (at least somewhat) and loosened by a cleaning crop that area can be planted to beans or peas the next year. Both fix nitrogen in the soil. When the harvest is done the plants should be roughly chopped and turned back into the soil at the end of the season.
These double rows of beans were planted a foot apart but now the growth is totally contiguous  (which will make picking a pain)

The following year that area is then ready to be planted to greens which benefit from the extra nitrogen and what is now starting to be friable soil, good for the fine seeds of lettuce and other greens like kale, mustard and arugula.

The final group of crops to be planted in that area is the root crops like beets and carrots which need soil that has a good tilth so the roots can grow down easily and, especially for carrots, straight. Raised beds can be also be helpful for root crops. Beets are partial to a little sprinkling of wood ash too.

But of course the plot thickens when you take into account members of the same family which should not be planted in the same area in consecutive years. So tomatoes and eggplants can't go where potatoes were for at least three years. And of course I always seem to miss some potatoes when I am digging. These then overwinter and pop up the next year totally ruining my best laid plans. Ultimately all of my beds seem to be partially potato beds...

And I have read that because tomatoes are perennial in their native countries they like it best if kept in the same bed at least two years. Other people absolutely insist that tomatoes must not be in the same soil for at least four years.

There are no hard and fast rules. Just lots of general principles and an infinite number of opinions. I have seen garden plans with 4 different beds but 8 and even 16! And most rotation plans show a four year schedule but some three years and other much longer. The permutations are endless...And unlike a crossword puzzle there isn't always the satisfaction of coming up with perfect solution!

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