We talk about green manures and how important they are for the soil all the time, but the logistics of getting the seed into the ground can be daunting, especially on a large scale, so we decided to share how we did it this week in the nursery.
Carr’s Organic Fruit Tree Nursery is made up of three different blocks, and at any given time one of them is fallow.
This is the perfect time to plant a green manure crop to restore soil fertility,
replenish the soil, and replace the organic matter we’ve removed by growing and harvesting hundreds of fruit trees.
After hearing soil scientist Dr. Christine Jones a couple of weeks ago and learning more about the importance of multi-species groundcovers, we got inspired to ramp up our green manure seed mix even more than usual. More on that in a moment, but first, how do you actually prepare the soil?
We’re lucky enough to have equipment, so Hugh jumped on the tractor and first up used the disc plough to turn in the weeds that were already growing. You can see the result in the first photo above.
Those weeds were in effect the first green manure crop, which we’re now following up with a more diverse plant mix that will hopefully stay green over summer.
We’re always wary about using equipment like discs, harrows or rotary hoes because of the way they smash up the soil and can damage microbes, particularly soil fungi.
But you’ve also got to find a way of getting the seed into the soil, and Dr. Jones was very much of the opinion that it’s worth disrupting the soil (albeit as minimally and infrequently as possible) to get diverse, perennial groundcover crops established. The benefit should quickly outweigh the initial cost.
The disc did a good job of turning most of the weeds in, but it was still too rough for the seeds to connect with the soil well enough, so next we put on the rotary hoe.
You can see the difference just one pass with the rotary hoe makes (on the left hand side of the photo above). It’s still not a super smooth seed bed, but it’s good enough for the seeds to hit the soil when they’re broadcast, rather than getting stuck on a clump of grass – where they definitely wouldn’t germinate and grow!
If we had seed-drilling equipment that could inject the seed straight into the soil we wouldn’t need to do this step, and in fact many innovative regenerative farmers are sowing seeds directly into pasture these days, with no soil disturbance of loss of ground cover at all, and getting excellent results.
But needs must, so the next step is broadcasting the seed by hand. It’s always a challenge to scatter the seed evenly over a patch this size, but by dividing the patch into sections and weighing out portions of the seed mix we got a pretty even spread.
The last step is raking the whole patch to get a light cover of soil over the seeds, and finally give the whole patch a really good watering in.
We’ve always used a fairly diverse mix of seeds for the green manure, but this year we went nuts! We were also influenced by Dr. Jones to make a couple of other modifications – we mixed in a good dose of worm castings out of our worm farm, and then we soaked the seeds in raw whey (sourced of course from Sellar Farmhouse Creamery) for a couple of hours before we sowed. These are both great sources of microbial innoculation to help the seeds get the best possible germination rate, and because we had access to both we gave it a double whammy!
This left the seed mix pretty wet, so then we mixed it with enough dry sand to make it spreadable.
The reason we were inspired to increase the diversity of our green manure seed mix was that Dr Jones explained that prior to European invasion, “the natural grasslands that once covered vast tracts of the Australian, North American, South American and sub-Saharan African continents – plus the ‘meadows’ of Europe – contained several hundred different kinds of grasses and forbs.”
Several hundred species! Imagine that!
A multi-species crop is an entire community of plants working together to convert sunlight into liquid carbon (remember learning about photosynthesis at school?) which it feeds the microbes in the soil. It’s called the plant-microbe bridge, and it builds soil, converts carbon from the air into stable compounds in the soil and holds far more water in the soil.
So, feeling inspired, we set out to create our own multi-species crop. We didn’t quite get to 100 species, but we managed 40:
- Alfalfa (lucerne)
- Broad bean
- Butterfly pea
- Kidney beans
- Lab lab bean
- Millet – French white
- Mung bean
- Soy bean
Now we just have to get them to grow! Stay tuned for photos….and if you’d like to find out more about how to quickly build fertile soil at your place using green manures, we’ve packed a lot more detail into this short course.