Friday, June 26, 2015

Crop rotation: Fruits to Roots to Legumes to Leafs


Growing the same crop in the same place for many years in a row disproportionately depletes the soil of certain nutrients. As I mentioned in last weeks post (here), crop rotation gives various nutrients to the soil, especially replenishing nitrogen in the soil. The focus on maintaining soil health ensures the health of the environment than more intensive systems brought on by Big Agri business. 
Other reasons for rotating crops include: preventing soil erosion and compaction of the soil, preventing the progression of pathogens and pests which occurs when one species is continuously cropped.

Plants that uptake a lot of nutrients from the soil include Cabbage, Cauliflower, Brussels, and Broccoli. Because of this, gardeners should follow these heavy feeders with light feeders such as root vegetables, or follow with nitrogen fixing vegetables such as peas and beans.

Perennial plants need no crop rotation, of course, so I am specifically speaking on summer and winter annual plants.
pic source: Growers learning

Crop rotation works best as a three or four year garden plan because "this is the number of years it takes for most soil-borne pests and diseases to decline to harmless levels" (growveg).
Beans, which uptake nitrogen from the air, add nitrogen to the soil. This is why many farmers grow beans one year, then corn is grown the following year in the same place, because corn uptakes a lot of nitrogen from the soil.
 "Every year the plants grown in each given area are changed, so that each group (with its own requirements, habits, pests and diseases) can have the advantage of new ground. If your beds are divided into four groups, this means that members of each plant family won’t occupy the same spot more than once in a four-year period" (growveg). 

Dividing crops into four main groups (legumes, roots, leafs, fruits) becomes too simplified when practicing crop rotation.  The growth habit of these groups does not bear on the classification of the plant. For example, potato and tomato are in the same family, so they may attract the same pests and uptake the same nutrients from the soil.

To begin incorporating crop rotation, first identify the crops you want to grow, and then keep plants of the same type together in one area. Remember that Brassicas follow legumes. For example, sow cabbage, broccoli, cauliflower on soil previously used for beans and peas. 

GrowVeg provides a crop rotation table that may assist you when growing in four different areas:

Area 1 Enrich area with compost and plant potatoes and tomatoes (Solanaceae). When crop has finished sow onions or leeks (Allium) for an overwinter crop.
Area 2 Sow parsnips, carrot, parsley (Umbeliferae). Fill gaps with lettuce and follow with a soil-enriching green manure during winter.
Area 3 Grow cabbage, kale, arugula (Brassicas) during the summer and follow with winter varieties of cabbage and Brussels sprouts.
Area 4 If this is your second or subsequent year, harvest the onions or leeks previously growing here over winter. Then sow peas and beans (legumes). When harvest has finished, lime the soil for brassicas which will move from area three to occupy the space next.

Incorporating polyculture and companion planting, such as the three sister's method, offers more diversity and complexity within the same season or rotation. The three sister's is a polyculture system where corn, beans, squash are grown together. While the corn grows tall, the beans vine up the stalks and replenish nitrogen to the soil, while squash trails on the ground to prevent weeds growing amongst the vegetables. For more details on polyculture systems like three sisters method, go to my post on Permaculture here, No money, work, or tilling involved: Permaculture.
Companion planting and crop rotation offer many benefits, especially when growing on Hugelkultur mounds. This is another permaculture technique which I discuss in detail in the link I posted above. Hugelkultur is a layering system of decaying wood which adds nutrients and water within the soil through the fungal activity in decaying wood. From my experience after growing food on Hugelkultur mounds for the first time this year, I am amazed at the growth and productivity. I highly recommend adopting Hugelkultur in place of tilling practices.  
Overall, the practice of crop rotation in sequence with companion planting and growing in Hugelkultur mounds will retain water deep in the soil, reduce watering while preventing erosion (maintains soil structure), avoids nutrient depletion in the soil, pests or soil-born disease, eliminating the use of fertilizers, and controls weeds. 

On a final note, keep records of your garden and successes and failures. Play the scientist role, and do experiments, make observations, conclusions. Remember when beginning crop rotation, that members of any given family should not be grown in the same sport for more than one year. Secondly, vegetables from different groups can share a plot if they require the same conditions.

The overall message here today is that these permaculture practices reduce environmental pollution, reduce greenhouse gases from food production, reduce or eliminate any unethical treatment of insects, animals, and the environment. 

5 comments:

  1. I'm going to ask what may seem like a ridiculous question, but I am being serious. The matter to make crops comes from the soil. In other words, crops are ultimately made from the soil they were grown in. When we eat the crop, we are taking that matter away from the soil. How do we put it back in? Should we use our own manure as fertiliser? Is this what farmers have traditionally done? Does compost made from materials found off the farm suffice instead?

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    1. In permaculture, chop and drop is a method of cutting weeds within or around the garden, which can be chopped and used as mulch. Of course you can grow yarrow or comfrey (some plant that fixes nitrogen) in and around the plants that are heavy nitrogen feeders. As always, Compost made from the leaf litter, grass clippings, food scraps creates better soil.

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    2. Humanure works well too. The seeds from fruits you eat will be put back into the soil because seeds from berries and things usually do not get digested.

      I'm not sure what farmers have traditionally done except use fertilizers, pesticides, etc, and also tilled and plowed the soil. Farmers now would consider these methods too sophisticated despite its simple appearance/strategy.
      What farmers have traditionally done depends on the region and time period. For example Masanobu Fukuoka, a Japanese farmer, practiced "natural farming" in the 1930s, using methods of crop rotation, guerrilla gardening (seed bombing), no tilling/plowing/weeding/fertilizing. Hugelkultur is an old method as well.

      "Chinampa system farming (sometimes called floating gardens) is a form of ancient raised field agriculture, used by American communities beginning at least as early as the 10th century AD. The word chinampa is from a Nahuatl (native Aztec) word, chinamitl, meaning an area enclosed by hedges or canes. The term refers today long narrow garden beds, separated by canals. The garden land is built up from the wetland by stacking alternating layers of lake mud and thick mats of decaying vegetation; this process is typically characterized by exceptionally high yields per unit of land".

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  2. Thanks. I'm glad you made this post about crop rotation. You may remember that I recently expressed concern that a vegan can only live self-sufficiently in a tropical climate. This belief was due to being influenced by a nineteenth century writer, August Engelhardt, who believed plants become more nutritious as one goes closer to the equator, since they have absorbed and stored more energy from the Sun over their lifetime, and that plants growing far from the equator have not stored enough energy for a human to live off them. This is partially true. Certainly, the banana and the coconut are very nutritious. However, I thought about it a bit more and realised there are very few well-known fruits that can be grown only in a tropical climate. There is the banana, the coconut, mango, papaya... that's about it. I found it hard to believe that this handful of fruits is the decisive factor between survival and non-survival. Instead of tropical fruits, I'm now an advocate for grains and legumes. Together, these can provide everything you need in your diet, and they can be grown all around the world. For example, you can live off just lentils and rice. In the Americas, people have traditionally lived off corn and beans (although I'm not sure this is a complete diet). And the same pattern is repeated worldwide.

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    1. It's amazing what our food has been modified to become. Grains were simply grass, bird seed, and now there is rice, quinoa, oats. What was only wild mustard has been artificially selected to become cauliflower, broccoli, cabbage, etc. Bananas have been modified over time to be less seedy (no seeds). In fact the wild banana looks hardly substantial to live on. There are so many tropical fruits, and it would be a great advantage to live in tropical locations. I find that I am more attracted to tropical fruit, as well, and I also believe that the tropical fruits from south America, or Hawaii, are very nutritious because of the rich soil.
      I truly would love to grow tropical fruit indoors/heated greenhouses/underground greenhouses, but this will take another 5-10 years.

      But certainly there are so many varieties of berries that grow well in cooler climates. Berries, peaches, pears, plums, figs, persimmons, grapes, melons, apples. Actually I have post on the uncommon fruits to grow for cold & temperate climates.

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