Experiment: Broadcasting cover crop seed over mulch?

Looking at ways to keep a constant cover of mulch or cover crop on permanent no-till raised beds in the tropics (Hilo, HI). We get 180+ inches of rain a year, pretty evenly distributed (2 rainy seasons each year, both are 6 months long...), 1400' elevation, average daily temperature is 72 degrees.

Have 68 beds of 125 sf each, that will be run through a rotation cycle, at the end of which they will go to cover crop. All beds are mulched heavily. Because of nutrient leaching, I want to keep a mulch or cover crop on the beds at all times. Being the tropics, nutrient cycling is pretty dang fast and mulch disappears in a hurry, so it requires more that just a chop and drop of a cover crop to keep things covered. I am moving towards supplementing the cover crop mulch (flail mowed) with transported mulch of white clover grown in dedicated areas in my pasture, see if that helps. Right now, am buying in green waste mulch from the city recycling center, costs $ and never really know what I am getting...

Enough intro, The Question:
Wondered if anyone has any experience with broadcasting cover crop directly over mulch, then "settling" it in with a roller or fluffing it up with a rake to get it to work deeper into the mulch, thereby eliminating raking back mulch to broadcast the CC seed. Since we get so much rain, moisture is probably not a problem in germination. When I have applied straw mulch, there has been a real bloom of the grain that bursts out of the straw, so I'm figuring to let that work for me and avoid the hassle of clearing the mulch, or using some sort of tilling.


Any thoughts/observations/guffaws appreciated...
David in Hilo

David MacKenzie wrote:Looking at ways to keep a constant cover of mulch or cover crop on permanent no-till raised beds in the tropics (Hilo, HI). We get 180+ inches of rain a year, pretty evenly distributed (2 rainy seasons each year, both are 6 months long...), 1400' elevation, average daily temperature is 72 degrees.

Have 68 beds of 125 sf each, that will be run through a rotation cycle, at the end of which they will go to cover crop. All beds are mulched heavily. Because of nutrient leaching, I want to keep a mulch or cover crop on the beds at all times. Being the tropics, nutrient cycling is pretty dang fast and mulch disappears in a hurry, so it requires more that just a chop and drop of a cover crop to keep things covered. I am moving towards supplementing the cover crop mulch (flail mowed) with transported mulch of white clover grown in dedicated areas in my pasture, see if that helps. Right now, am buying in green waste mulch from the city recycling center, costs $ and never really know what I am getting...

Enough intro, The Question:
Wondered if anyone has any experience with broadcasting cover crop directly over mulch, then "settling" it in with a roller or fluffing it up with a rake to get it to work deeper into the mulch, thereby eliminating raking back mulch to broadcast the CC seed. Since we get so much rain, moisture is probably not a problem in germination. When I have applied straw mulch, there has been a real bloom of the grain that bursts out of the straw, so I'm figuring to let that work for me and avoid the hassle of clearing the mulch, or using some sort of tilling.


Any thoughts/observations/guffaws appreciated...
David in Hilo

I tried it one year with winter rye. It didn't work.

Hi Scott,
What do you think the cause of it not working was?
David

David MacKenzie wrote:Hi Scott,
What do you think the cause of it not working was?
David

Poor germination.

I've done it two years in a row on top of wood chip mulch. The larger seeds, such as daikon radish, favas, and vetch have done quite well both years; smaller seeds such as clover and annual rye had very poor germination. This year, the second year I did it (without refreshing the wood chips, so they were more broken down), oats did VERY well along with the relatively large-seeded cover crops. The clover has better germination this year than it did last year, when the wood chips were coarser. These were all grown during the cold season.

Buckwheat did not germinate well for me last summer, but given the fact that some of the other smaller seeds had improved germination this winter, I'm going to try buckwheat again this coming summer.

Great to hear, Emilie!
Did you use any particular technique to seat the seeds in the mulch?
David

Hi Permies;
The best way to broadcast seed over mulch I came up with is seed balls (similar to masanobu fukuoka). I did that in the last 3 years first with radishes (large black varieties, daikon), than with rye, clover, wild flowers, comfrey and any other wild plant seeds that I used to rehabilitate the land. Fukuoka used seed balls over naturally mulched surface, while I used it over 5- 10 inch layer of wood chips, leaf, and kitchen waste. Seeds are already planted in seedballs there is no need to plant them again. First year I used way more seeds than recommended, expecting failure rate will be more like 90%. All of them germinated, creating a thick radish semi-forest. The land is almost pure clay, on a 20-30 degrees slope and south facing.
Since it was more like a torture than pleasure to make all those seed balls, I built a seed ball drum (search for Alfred von Bachmayr or Von Bachmayr Rotary Seed Ball Drum) . It is dismantled right now, but it is a heaven-send, producing seed balls for 1 acre less than 20 min.
I'll try to add some pictures, first time here so

Fantastic looking cover! I will have to go back through Fukuoka-san's book, kind of slipped my mind...

David MacKenzie wrote:Great to hear, Emilie!
Did you use any particular technique to seat the seeds in the mulch?
David

Well, the favas I kind of punched in using a heavy rake (it's a relatively small area, easy enough to do by hand). The others I simply broadcast and let settle on their own with irrigation/rainfall. Because the mulch was fairly coarse, they were able to find gaps and settle in on their own (plus, I didn't want them to get *too* deep in the coarse mulch, because I figured they'd have a hard time coming up then). If you're using a finer mulch such as straw, you might need to do a little more to get the seeds settled in.