Well, we are now starting our fourth season in implementing a no tillage system at the Farm. I have to say its been quite the learning experience. There are a number of nuances in doing this that have sort of evolved as we have gone. The first season we used no till we used a manually crimped winter cereal rye hairy vetch cover crop as mulch cover that we transplanted our flowers directly into. It really worked quite well at weed suppression and water conservation. The decaying root system of cover crop help soil tilth a lot. However, that year late May through the end of June was wetter than usual and we had a very large slug problem initially until the dry weather arrived in early July. Although the Zinnias struggled a bit they caught up quickly and yielded pretty close to normal. The later planted sunflowers also performed well and had little weed pressure.
Vetch and rye knocked down and ready for planting, using transplants only.
The soil under the vetch rye cover is loose and friable.
Our problems surfaced in the Fall when we tried to broadcast the next years cover crop. Most of the seed was devoured by birds and insects and we ended up with very poor germination. That second Spring we ended up applying compost and broad-forking the beds. Needless to say it was much more work but we still didn't use mechanical tillage. What we did notice though was that soil life, like worms, arthropods and other soil life was getting more robust. Unfortunately, that year we also had increased weed pressure and ended up weeding more than the year before.
After our second season what we realized is that our system of no tillage really needed several different methods operating in rotation with each other. In our third season we did two additional things. The first was implementing a system of Occultation. Using just a crimped cover-crop alone we realized that reseeding the next years crop would be more effective on soil that had lower biomass on top such that the seed could be gently covered by light raking. So that is when we turned to Occultation. This process has been used by Organic Farmers and others for years and what got me thinking about it again was how Jean Martin Fortier of Les Jardin De la Grelinette had integrated this practice into his cropping system. With some modifications for our row system we found this method to be an excellent way to get the soil life to do the work of eliminating crop residues. Simultaneously it also helped reduce weed pressure, improved tilth and gave an excellent bare ground seed bed.
As we discovered how to effectively use this for removal of our cash crop residues we also learned how to effectively work in rotations of cover-crops like buckwheat or clover. We began to realize that using this system on some beds and the over winter cereal rye/vetch system on others would be an effective rotation scheme . Its important to note that Occultation is used year round. By trapping moisture under the tarps, eliminating sunlight the good bugs thrive and can consume huge amounts of biomass in just a minimum of 3-4 weeks. We have found that soil tilth is improving dramatically on our heavy clay-silt soil.
Checking the soil depth for friablity or looseness.
At this point this bed is about 14 inches of nice loose soil with no mechanical tillage. Please note all this bed prep was done on Feb 24, 2015.
The important objective that we are trying to achieve is minimum disturbance of the soil, period. What we want to get away from is any kind of lifting or turning of the soil. Pictured below is a bed we tarped at the end of the season last November and are at a point to begin prepping this for Spring Larkspur. Bed prep entailed removal of the tarp, hand broadcast of basic minerals/feathermeal, a top dress of 1/2" compost then using a spading fork we quickly went through and just did what I call cracking the soil. What this means is slipping the spading fork or broadfork in and just giving it a rock back forth motion then move 6"-12" and do it again down the row. What we have found is that method gently allows the minerals and compost to get lightly dropped into the top of the soil. You'll notice from this picture that our drip lines were left under the tarp in place so when the tarp is removed we are good to go to plant fairly quickly. Total time to prep the 100' long 30" wide bed, not counting spreading the compost, can be about 45-60 minutes and your ready to plant. I'm sure the younger folks can move a bit faster!
Mudpuppies or salamanders like living under the tarps feasting away on slugs and other goodies.
Working the minerals in with a fork. Notice the drip lines are in place. Once the minerals are forked in, we are ready to plant.
So as an example above when the Larkspur is harvested we will manually knock down the remaining residue, probably apply 1/2' compost over the top, thoroughly soak the bed, and apply the tarp. In about 4 weeks we will remove the tarp and probably plant sunflowers as the next rotation with an under sowing of berseem clover or we will under sow the cereal rye/vetch winter mixture, if it is at least late August. If the under sown cover crop was berseem, we would cut the sunflowers at harvest as close to the ground as possible, with any culls get dumped back on the bed, and then tarp the bed again for a minimum of 4 weeks. Depending on the case this bed could be used for fall plantings of biennials or leaving the cereal rye/vetch mix through the winter.
This is an example of the cereal rye/vetch cover sown around Labor Day 2014. Photo was taken on 2/25/15
We have also used Occultation to reclaim beds that were heavily infested with noxious perennial weeds. Our favorite here on the farm is Canadian thistle. This weed spreads by seed and rhizome. We had one bed last year that we tarped for 4 weeks at just the time the thistle was beginning to grow. When we removed the tarp the first time there was some of the weed that had tried to grow in the dark but was a sickly yellow. We raked these off and then sowed a buckwheat cover crop. We grew this for 4 weeks and knocked it down (high tech...we used our feet) wetted the bed thoroughly and tarped it again for 4 weeks. After the second tarping (it was mid July by this point) we could find very little evidence of thistle. So we took the risk and planted a crop of Fall Marigolds. We had a few sickly thistle volunteers at the edge of the bed but the canopy of the marigolds kept the environment shaded enough that we saw no weed pressure in the center of the bed.
At this point we are 100% no till on our established beds and only use mechanical tillage and our bed former in late August before our Fall rains come to initially create new beds . Our long term goal is to build our organic material content to between 5-7 % and to balance the minerals and micro-nutrients. We think that on many of our areas once we reach a good organic material level we should be able to maintain this with crop residues in place and use of cover-crops in all seasons with little or no purchased compost. This is a work in progress so will keep working on this and fine tuning it.