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Tuesday, February 3, 2009

No Till Farming Rotation

Reduced Tillage at Seven Seeds Farm

Tilling the soil eliminated the earth’s natural protective biological cover of vegetation to create a weed free environment in which farmers can grow crops. It releases abundant nutrients to those seasons’ crops by allowing organic matter in the form of humus to become mineralized by sunlight and water forces. Repeated tilling exhausts the soils natural fertility, thereby forcing the farmer to apply fertilizer, usually composted animal manures and cover crop green manures on an organic farm. Nonetheless, these practices do not have a long track record of sustainability. Contemplate how long tractors have been in wide usage (maybe 50-60 years). Traditional farmers had to preserve much more land as pasture to feed draft animals for power. Usually this amounted to 2/3rds of a given mixed farm. Tractors changed this whole systems approach by freeing up that land for the growing of crops, which could be sold, and eliminating animals from the fertility loop on many farms. Consider one cow can produce enough manure to fertilize one acre of high production vegetables. However, it requires 4 acres of grass to pasture and produce hay for that one cow (now you can see where the 2/3 -> ¾ pasture based whole system farm model). Assuming farmers are not yet willing to forfeit their tractors for draft horses (which actually carry a larger ecological footprint if the farmer has to buy in hay than using biodiesel in a tractor. Remember a horse is like a tractor “idling” all day,) how can we develop a more sustainable model of vegetable farming?
I have experimented with no till small scale farming for a few years. I am actually doing a reduced tillage system as I learn what works for me. I have 7 years of very active soil improvement (cover cropping, rock dusts and lots of biodynamic compost) into our clay loam soil. I doubt that the project I describe next would be successful on a rougher soil. We grow seeds for Seeds of Change in blocks that are about 1/8 an acre (30' x 100') and I am developing a no till rotation scheme with this plot size. A few years ago I had a block of tomatoes I had grown for seed. Normally I pull the trellising and disc it all under in the fall and sow rye, peas and vetch over the winter, which is mowed or grazed down in May and then disced and tilled and compost spread (at 15yds/acre) to make beds.
My experiment began by doing my normal soil prep/cover crop regime as described above on one half of a block and on the other I simply left the tomato beds sit over the winter (they had been mulched with straw when the tomatoes were planted) and then I pulled the vines in the spring (very easy to do by then) and I transplanted lettuce plants for seed (3 rows on a 4 foot wide bed) into both the tilled (cover cropped and compost applied) and untilled/mulched (no cover crop or compost) beds side by side 4 beds of each. It was a little trickier transplanting into the untilled beds, but a right angle trowel made the job doable. Amazingly the transplants in the untilled beds took off right away growing vigorously while the ones in my fluffy spaded beds sat there for about 2 weeks until they began growing again.

My hunch is that the undisturbed soil flora/fauna/fungal populations were intact in the untilled beds and took a while to recolonize the tilled beds. What really surprised me was that after this initial growth the untilled ones produced larger heads and more seed even though they didn't benefit from the compost and nitrogen rich cover crops that the other beds received.

What I want to try next is including a cereal grain in the rotation, so that my straw is grown in place. A conceivable 5-year rotation might look like:

1) Fall sown Rye/Oats/wheat possibly with a legume like dry peas,
* This would be ready for harvest in June/July, graze chicken/ducks/turkeys to clean up left over grains, then
2) Plant summer crop from transplants into straw
3) Garlic in the fall
4) Broadcast buckwheat before forking our garlic, so that it is planted when you pull garlic, grow buckwheat to seed, harvest some and clean up the rest with poultry.
5) Plant a winter crop of fava beans (seeded in early October) to be harvested in May/June then back to another summer crop
6) Plant summer crop in June (tomatoes, or vine crop)
7) Plant grains in the fall

Over the course of five years you could get:
* 3-grain crops
* Poultry clean up opportunity in between each
* Fava Bean crop
* Garlic Crop
* 2 summer crops

A total of 7 vegetable crops and also animal products within 5 years. Now if I could only pull it off within a commercially viable farm. I have done aspects of this rotation but never in a seamless cycle.

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