One thing I hear a lot about (and teach my agriculture volunteers) is the method of double digging for garden beds. It’s a lot of work, but there’s a bunch of reported benefits, so that’s one of the main reasons we keep teaching it, even though it can be a bit hard to convince people of it’s usefulness for the amount of work it takes. In this time during quarantine, where I’ve been working on updating our training sessions as I have no volunteers, and so wanted to dig (haha) a bit more into double digging to see if it’s really worth all that fuss. I was surprised not to see that much info here on ECHO community, or in a lot of academic journals, though I did see one or two articles in some African journals that unfortunately I was unable to access.
So, if any of you and give me anecdotal evidence or can point me in the direction of reports/experiments of benefits (or lack thereof) of double digging, that would be most helpful.
Generally I’ve heard:
–the loosen soil makes a better aerated zone for deeper root growth
–the addition of manure/biochar/etc is helpful nutritionally, and enhances the soil properties
–it can extend your growing season, particularly if surrounded by pits and trenches, as the loosened area with amendments will act as a sort of basin to store water in. (I think perhaps deeper roots could also come to play in being able to hold out longer in dry conditions.)
– Conversely, I’ve also heard that it helps with drainage.
–by double digging you are careful to maintain topsoil on top, so it’s better than just general tilling.
I’ll be very interested to hear from the community also, particularly to gain reliable resources. This option is taught in various regions of the world, but you are correct. There is not much available in the way of published research that I can find, either. Here are a few additional resources collected in ECHOcommunity that may be helpful to the conversation. https://www.echocommunity.org/resources/5caa5860-323a-4a89-83de-110f0b63d655
Desde los años 70 estuve muy entusiasmado con el BIG, pero mi conclusión es que no funciona igual en todos lados, además el esfuerzo es demasiado, en las zonas donde llueve mucho no es cierto que se mantiene esponjoso por 3 ó cuatro años como algunos aseguran. Creo que es importante mirar del otro lado a los métodos que no excavan del todo, un buen punto para comenzar es con Charles Dowding, y Paul Gautschy.
Una buena señal de que un método es bueno consiste en que se propaga mucho sin necesidad de promoverlo mucho, y por lo menos en la región donde vivo eso no ha ocurrido, a pesar de algunos intentos de promoverlo. Hay varias referencias que ponen en duda lo que se dice acerca del aumento sorprendente de los rendimientos:
Personalmente prefiero no excavar, cuando las diferencias no son significativas, me quedo con las opciones de no excavar, de paso la naturaleza no lo hace.
In the tropics, tillage in general, and especially double digging, rapidly accelerates the decomposition of organic matter in the soil, which can be problematic. Surface application of compost or fresh organic matter (chop and drop) is probably preferable in the tropics.
Hi Laura, Dawn reminded us today that ECHO had published info in EDN #10 on “hugelkultur” or hill culture – http://edn.link/edn10 (“Some thoughts on Composting”). This could be a possible alternative to double digging. There is plenty of information on the internet about the technique.
Wil wrote something in Spanish and I read Spanish and then I did a google translate since I am not perfect with every word. Here is what he says “Since the 70s I have been very enthusiastic about the Double Digging, but my conclusion is that it does not work the same everywhere, also the effort is too much, in areas where it rains a lot it is not true that it stays spongy for 3 or four years as some claim . I think it is important to look the other way at methods that don’t dig at all, a good place to start is with Charles Dowding, and Paul Gautschy.
A good sign that a method is good is that it diffuses far and wide without having to promote it a lot, and at least in the region where I live that has not happened, despite some attempts to promote it. There are several references that question what is said about the surprising increase in returns.”
Let me add a few comments since I agree with Wil in what he has said. I have used the system when I have had very poor soil in my home landscaping in town and I would bring in a bunch of leaves and put some soil over the top and then some fertilizer on the outside edge of the organic matter and then plant. In that case it worked wonders for many years of high fertility without much effort at all. This double digging method is particularly good for trees (leave a divit when you can to put your mulch in) and it is basically the same thing as the Zai hole method and I have modified the Zai hole to Zai trench when crops are to be planted at closer spacing. You need organic matter, you need charcoal if you can get it and if not then some wood ash a tablespoon when plants are planted closer and 2 when further apart. Use human urine when using seed a little on the outside edge of the organic matter and if using transplants wait two weeks and then wait again for cloudy weather and add a very small amount of urine on the outside edges of where you put the organic matter. It does not make sense to use double digging for agronomic crops and I don’t think it makes sense to dig down double deep even for vegetables (unless you have a very small garden and if you do perhaps you should look for additional land you can access or team up with someone else) when a layer of organic matter from one shovel depth will work wonders for you but two shovels depth is too much work relative to good results from less depth and putting in a layer of leaves or weeds or anything brown that is organic. The urine will restore your soil to nice compost with plenty of fertility. I have never composted anything in my whole life because I have found it unnecessary to go to all that trouble. If I have something organic or store something organic it may compost some until I can use, ant then it gets used as mulch or goes in a planting hole. Let’s mulch but not compost since you can grow on a lot more acreage if you avoid the labor of composting by just adding urine (at small amounts at a time) to anything you have put in the ground after you have placed the organic matter in the hole or trench.
Hi Laura - I grew up in England in an area where there were heavier soils. My grandfathers and father always said that you doubled spaded to open new areas. This brought up minerals and also allowed root crops to go deep and bring up more nutrients. You double spaded, then planted potatoes the next spring and forked the hills as you harvested. Everyone grew potatoes first time around to break up the soil. BUT you will notice the planting was for the next spring - so these big clods of earth sat through a winter of frost which broke up the soil. My dad bough a rotatilla but it wasn’t as good as the old method - it didn’t go deep enough - and so the deep soil either sat there or was compacted into a hard pan of clay. (And we were lucky because the land had once been part of a livery stable right into the 1930’s/40’s.)
I tried this same method in Toronto when I had a garden there and it worked fine. I wouldn’t try it here in Cuba - the soil tends to go to fine powder and loses all of its nutrients with heavy rain.
Lewis Mumford tried similar methods at Malabar Farm - trying to restore the land which had been destroyed by growing corn over and over and plowing up and down hills. He also used alfalfa to go deep and pull up nutrients and minerals. Worth a look at the documentation there at Malabar. Also worth reading Ploughman’s Folly.
