Experimental Garden

Jul 24, 2016 18:16:53

Hi All,

I wanted to share this project with you all at Weaton Labs. I live in VT at an intentional community called the Center for Transformational Practice. Its a small community that tries to meld spirituality and meditation with sustainability. There are a lot of gardeners in the area that are friends of the community and as you may have noticed there are as many opinions on what the best gardening techniques are as there are gardeners. Although I escaped long ago to become a carpenter I do have a background in Chemistry, so I decided to try to take the opinion out of two gardening techniques by using scientific design to do a controlled experiment. I wanted to test both Hugelkultur as well as no-till gardening.

I set up an experimental design so that two variables can be tested using only 4 trials (see the attached pdf). The beds all have the same soil mixture and amount. The soil is 50% finished compost and 50% sandy loam. Two of the beds have a mulch cover that consists of small branches and leaves (chipped) from a medium sized Box Alder. The mulch is about half green leaves and half ramial wood chips and is already composting at the soil surface. Beds B and D are no-till, mulch covered. The two right hand beds (beds C and D) have about a foot of box alder wood under them. I have more pics of this if you are interested. I've been taking a lot of pics of the plants progress over the Summer.

All the plants are the same variety and are placed in the same relative position in each bed. I have been watering the beds as needed, but if I add 4 gallons to Bed A, I'll also add 4 to bed C etc. So far the mulch covered beds only have needed about 1/2 the water of the bare dirt beds. I weighed the mulch and made sure that beds B and D had the same amount of mulch, and this fall I'm going to till in an equal mass of finished compost to beds A and C. I've also been weighing the weeds on each bed. Not too many weeds so far. I've also been taking height measurements each week, and will plot those out as growth rate for each bed. I should have gotten the soil in each bed tested at the beginning but I am not into becoming rich so I don't have that much money.

It might sound crazy to test it this way, but the beauty of this design is that for each parameter being tested, (like pounds of tomatoes for instance), you get two trials. Subtracting the weight of tomatoes of Bed C from bed A is one test for the hugel variable as well as subtracting the lbs of tomatoes of bed B from bed D. The no-till variable will have two trials as well. By Subtracting Bed C from Bed D and bed A from bed B both will give data that should be due only to whether or not it is no-till(mulch covered) or tilled (bare dirt).

So far the best bed is bed D (hugel and no-till) followed by bed B(regular and no-till) followed by bed C (hugel tilled), and bed A (regular tilled)

A few surprising results however. The tomatoes and peppers did a little better in the bare dirt beds at first. I think it was because of the hotter soil. We are in VT and the soil tends to be cooler in the early summer.

I don't want to bore you with all the gory details, but its been a lot of fun. I hope other people want to do similar experiments testing hugelkulture and no-till. I have had a lot of great results with both techniques over the years, but since it wasn't a controlled experiment it can't be said with certainty that it was the wood underneath that had the effect unless you had another bed just like it without wood underneath to compare it to.

So let me know what you think and if you are interested in replicating this experiment or modifying it or if you have done anything similar in the past. I would love to hear about it. It would be cool to see some solid evidence that goes beyond opinion.

Jul 25, 2016 09:39:17

I find this very interesting. I have been doing no till, mulch beds or years. I have 3, 4 x 50' beds that are doing ok. I just put them in last fall. Have amended with composted wood chips, mushroom compost, and hay twice. As I know it will take a bit for it to really take off, I've done it before. I'm contemplating digging in and doing hugels. It's a lot of work, I have the material on the property. Would you say go for it per your experiment? Lots of brush and dead trees down that I need to do something with. Sitting on the fence post.

Jul 25, 2016 10:43:38

@Karl R.: "Subtracting the weight of tomatoes of Bed C from bed A is one test for the hugel variable as well as subtracting the lbs of tomatoes of bed B from bed D. The no-till variable will have two trials as well. By Subtracting Bed C from Bed D and bed A from bed B both will give data that should be due only to whether or not it is no-till(mulch covered) or tilled (bare dirt)."

Looks like a nice design, Karl. I can see where this would provide some useful information for those wanting to test out scenarios for their own operation. One concern would be with the treatment replication within the experiment. For example, although I can't see the whole area of study to be sure, it looks as if there is some shade creeping in at the left side of the photo. This would put bed A under shade earlier than the other plots....maybe? Although it may be an ugly increase in work to do so, if you were to replicate the beds at random, increasing the experiment to 12 beds so that each bed-treatment was replicated 3 times, it may reveal (or reduce) variability between readings that would be attributable to "noise", bed location, or otherwise in the experiment. In addition (no pun intended), as noted in the clipped statement above from your post, there often are variables that are not additive....cannot be separated out by simple addition and subtraction:

"A problem with data that we actually look at is that you do not know in advance whether the effects are additive or not. Because of random error, the interaction terms are seldom exactly zero. You may be involved in a situation that is either additive or non-additive, and the first task is to decide between them." -- https://onlinecourses.science.psu.edu/stat503/node/31

So for example the variable "mulching" might provide a plant-yield benefit, the variable "watering" might provide another yield benefit, but under certain conditions, put the two together and you may get over-saturation of the soil and see a yield penalty due to increased root rot or anoxia. Not the best example, but something to be aware of. Nevertheless, for bulk effects that give a good starting point for other tests and trials, a nice layout here.

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