Hole prep for the next grow - a discussion

[DTOM420]

I’m digging some big holes in preparation for next year and I thought a discussion of holes in the ground and the soil prep to fill them would make for an interesting topic. We all have our individual challenges and goals; so there are undoubtably as many approaches to preparing sites as there are soil types and environments.

Here’s my situation:

Grow type: Semi guerilla grow
Latitude: 28.5°
Native soil: significant clay and alkaline (7.7pH). Very compacted below 18” Topsoil is very fertile aside from those issues.
Water source: Well water that’s alkaline (7.8pH) w/ hardness of 6 grains/gallon. That’s about 100ppm of calcium & magnesium.
Goal: To grow some really massive photo plants
Rainfall: Minimal but we can (and do) get some torrential downpours occasionally. They can drop 2-4” in a few hours and the water “runs” quickly due to the soil and a decent slope.

So, since I want my plants to have every chance to maximize on their growth potential, I’m digging some pretty big holes. They’re about 7’/2m wide and 3’/1m deep. Let me tell you...it’s NOT a fun project doing this in 38°C/100°F temperatures with a shovel and a pick! Lol!

Obviously, my native soil won’t work as is. It turns to concrete. So, I’m going to amend it with lots of compost (60%), composted horse and chicken manure, perlite (15%), gypsum & green sand (to break up clay and release nutrients), sulphur and sphagnum peat moss to help acidify the native soil and other nutrient rich amendments. Since my water source is alkaline I thought I’d try to get the soil on the acidic side (pH6) of what cannabis likes, in order to buffer the water and (hopefully) provide a happy growing environment around pH6.8. If this isn’t a solid plan, please let me know.

My biggest problem is the clay soil. Sure, I could even completely replace the soil in the hole with something perfectly suited for growing, but that giant hole is basically a bowl without much drainage. Like trying to grow in a bucket without any drain holes. The clay in the native soil prevents good drainage. If we get one of the 10-12cm/4-5” turd floating rains we get from time to time, those holes will be holding an awful lot of water at the bottom. Especially if it runs downhill and finds my holes to drop into. My plants could find themselves suddenly living in a pond! At first, I thought about digging drainage ditches to let water escape; but that’s just TOO much work - digging a 1m deep ditch for 10-12m? NO THANK YOU! Lol. So, I came up with a couple ideas to deal with any heavy rainfalls. The first idea was to build a berm around the hole. Using the dirt I excavated from the bottom of the holes, I built a 34cm/12” high berm around the edge of the hole. This berm will force water to flow around the hole instead of into it. Sure, I’ll catch the rain that falls but not the water that’s running. It also makes my holes even deeper! If I backfill all the way to the top of the berm height, my plants will have about 134cm of soil below them!

My next trick/experiment is a pedestal than I left at the bottom of the hole(s). Check out the picture below. Basically, it’s a reverse doughnut shape. The 15cm-20cm pedestal in the middle is that compacted native clay filled soil. My hope is that this compacted soil will serve as a ‘stop’ for any tap root that grows that deep and that the surrounding channel will catch the majority of a major rainfall; keeping the rootball from getting too waterlogged in the event of a major downpour. Do you think the majority of the root ball will remain above that pedestal if a tap root doesn’t go any deeper after hitting the pedestal?

The last thing I thought I’d try is setting several lengths of 4” pvc pipes, with drain holes, into the outer rim of the hole. I’m going to make a cutout at the bottom as well, so I can reach down and see if moisture is reaching the bottom of the hole, when we’re at the height of the summer heatwave. If water from the surface irrigation isn’t getting down there I’ll know it and I could even fill the pipes with water to provide moisture (or nutes) to the bottom. Also, I’ll be able to see if a heavy rain has left standing water at the bottom of the holes - letting me know when it’s safe to water again. .

Here’s a link to a quick video (Vimeo) of the hole with a brief explanation:

They don’t look big in those pictures but they’re the size of 2 man foxholes. I could barely climb out. Lol!

I’m all-ears if anyone has suggestions or a critique of my plan. The soil amendment to really another topic and something I’m still playing with. My focus here is the actual hole itself; and how it works for the challenges I have at my grow site. Hopefully it may help someone else with similar soil; even if they want to do it on a smaller scale. Digging these by hand is NO fun; and filling them with high quality soil sure isn’t cheap. Hopefully, it’ll all be worth it, though!

How do YOU prep your holes and have you come up with any tricks to compensate for your particular environmental challenges?

 

[G.Leave]

I’m digging some big holes in preparation for next year and I thought a discussion of holes in the ground and the soil prep to fill them would make for an interesting topic. We all have our individual challenges and goals; so there are undoubtably as many approaches to preparing sites as there are soil types and environments.

Here’s my situation:

Grow type: Semi guerilla grow
Latitude: 28.5°
Native soil: significant clay and alkaline (7.7pH). Very compacted below 18” Topsoil is very fertile aside from those issues.
Water source: Well water that’s alkaline (7.8pH) w/ hardness of 6 grains/gallon. That’s about 100ppm of calcium & magnesium.
Goal: To grow some really massive photo plants
Rainfall: Minimal but we can (and do) get some torrential downpours occasionally. They can drop 2-4” in a few hours and the water “runs” quickly due to the soil and a decent slope.

So, since I want my plants to have every chance to maximize on their growth potential, I’m digging some pretty big holes. They’re about 7’/2m wide and 3’/1m deep. Let me tell you...it’s NOT a fun project doing this in 38°C/100°F temperatures with a shovel and a pick! Lol!

Obviously, my native soil won’t work as is. It turns to concrete. So, I’m going to amend it with lots of compost (60%), composted horse and chicken manure, perlite (15%), gypsum & green sand (to break up clay and release nutrients), sulphur and sphagnum peat moss to help acidify the native soil and other nutrient rich amendments. Since my water source is alkaline I thought I’d try to get the soil on the acidic side (pH6) of what cannabis likes, in order to buffer the water and (hopefully) provide a happy growing environment around pH6.8. If this isn’t a solid plan, please let me know.

My biggest problem is the clay soil. Sure, I could even completely replace the soil in the hole with something perfectly suited for growing, but that giant hole is basically a bowl without much drainage. Like trying to grow in a bucket without any drain holes. The clay in the native soil prevents good drainage. If we get one of the 10-12cm/4-5” turd floating rains we get from time to time, those holes will be holding an awful lot of water at the bottom. Especially if it runs downhill and finds my holes to drop into. My plants could find themselves suddenly living in a pond! At first, I thought about digging drainage ditches to let water escape; but that’s just TOO much work - digging a 1m deep ditch for 10-12m? NO THANK YOU! Lol. So, I came up with a couple ideas to deal with any heavy rainfalls. The first idea was to build a berm around the hole. Using the dirt I excavated from the bottom of the holes, I built a 34cm/12” high berm around the edge of the hole. This berm will force water to flow around the hole instead of into it. Sure, I’ll catch the rain that falls but not the water that’s running. It also makes my holes even deeper! If I backfill all the way to the top of the berm height, my plants will have about 134cm of soil below them!

My next trick/experiment is a pedestal than I left at the bottom of the hole(s). Check out the picture below. Basically, it’s a reverse doughnut shape. The 15cm-20cm pedestal in the middle is that compacted native clay filled soil. My hope is that this compacted soil will serve as a ‘stop’ for any tap root that grows that deep and that the surrounding channel will catch the majority of a major rainfall; keeping the rootball from getting too waterlogged in the event of a major downpour. Do you think the majority of the root ball will remain above that pedestal if a tap root doesn’t go any deeper after hitting the pedestal?

The last thing I thought I’d try is setting several lengths of 4” pvc pipes, with drain holes, into the outer rim of the hole. I’m going to make a cutout at the bottom as well, so I can reach down and see if moisture is reaching the bottom of the hole, when we’re at the height of the summer heatwave. If water from the surface irrigation isn’t getting down there I’ll know it and I could even fill the pipes with water to provide moisture (or nutes) to the bottom. Also, I’ll be able to see if a heavy rain has left standing water at the bottom of the holes - letting me know when it’s safe to water again. .

View attachment 945320 View attachment 945321

Here’s a link to a quick video (Vimeo) of the hole with a brief explanation:

They don’t look big in those pictures but they’re the size of 2 man foxholes. I could barely climb out. Lol!

I’m all-ears if anyone has suggestions or a critique of my plan. The soil amendment to really another topic and something I’m still playing with. My focus here is the actual hole itself; and how it works for the challenges I have at my grow site. Hopefully it may help someone else with similar soil; even if they want to do it on a smaller scale. Digging these by hand is NO fun; and filling them with high quality soil sure isn’t cheap. Hopefully, it’ll all be worth it, though!

How do YOU prep your holes and have you come up with any tricks to compensate for your particular environmental challenges?

Hey man....when i have some spare time i am going to get right into this thread...you do indeed have some uniques challenges, and you have some great ideas on how to overcome the challenges. When i was reading it, your burm idea was exactly what i was thinking would be a solution.

Hardwood leaf compost - do not overlook rotted hardwood leaves!! Go to a forest and scrape back a few leaves and check the dirt from the rotted leaves. Prime dark brown or black, would work great for your situation to help break up the consistency of the clay, and potentially you might have a source close to the grow site.

 

[G.Leave]

Repped for all that work.(cant rep until i pass out to somebody else!)

 

[DTOM420]

Repped for all that work.(cant rep until i pass out to somebody else!)

Thanks, brother! Always respect your input! That crazy rain period really stopped progress on the holes. Lol! I need to get back to digging but I’ve been working on composting for them lately. It’s gotten busy at work too. Time is going to be very limited for the next few months. Ugh.

 

[Exotic Flower]

Wow. That's some serious digging.



I think your berm idea is good.
And the 4" PVC pipe check thing.

I was reading because I have maybe the opposite prob.
(Thread in this same sub-forum...)

I'm not sure about the pedestal idea.
Maybe.
What if the lower donut shape was filled with gravel or stones?
Would that provide more space for water to drain into?

 

[DTOM420]

Wow. That's some serious digging.



I think your berm idea is good.
And the 4" PVC pipe check thing.

I was reading because I have maybe the opposite prob.
(Thread in this same sub-forum...)

I'm not sure about the pedestal idea.
Maybe.
What if the lower donut shape was filled with gravel or stones?
Would that provide more space for water to drain into?

Thanks Maria!

Yeah, I’ve been thinking about adding gravel at the bottom. Or some river rock, to be specific. Ugh, that’s a lot more work! Wish I had a big tractor. lol! I think the tap root would penetrate the pedestal after all. So, that makes it useless. Lol. Another possibility is covering the pedestal with some plastic. The main idea is to keep the tap root from going any deeper than a certain point. Still got some thinking to do on this.

The berm is going to need to reinforcement. We had some incredible rain (even more than the kind I’ve been trying to prepare these holes for) and there’s been some serious erosion of the berms. So, I’m considering sewing up some fabric to use as an erosion control around the outside OR buying done 200 gallon grow bags and cutting out most of the bottom. This would contain the soil. Again, something I’m thinking about. It’s a learning process.

I’ve been on a break from digging. First we had a torrential rain event that deposited a year’s worth of rain in less than 3 weeks and then I got super swamped at work. But, this is why I started early. I’ve been really focused on the soil that will go back into the holes. I’m going all organic and have been doing loads of research. We’ve got a pretty good discussion going on over in the Organic section in my Mycorrhizae thread. Come join us if you’d like!

 

[Exotic Flower]

@DTOM420 -- wow. From the sound of that rain, your preparation is needed.
I thought it maybe a bit too much at first, but now, probably not!

Tractor. Yes. You need a tractor.

 

[Exotic Flower]

@DTOM420 -- how are the holes and plants going? Manage to defeat the rain and flooding?

 

[puffy]

Growing near to the Sea I have a regular routine for what I do with my holes when packing them up for the winter.

Beforehand I have picked a lot of seakelp and seaweed, which I've had outside so rain can flush the salts. I then chop it up and add it to the holes.

Also I fish a lot of these small fish you get nearby shore in Norway (add some mussel to the hook and you get a bite every time, can pull up 30-40 in an hour).

I chop these up as well, add lawnmowed grass and mix it all up in the hole. Then I spread a layer of mulch on top to aid with heat creation (put your hand in a pile of mulched grass, the gasses generate heat).

Holes just keep getting better and better, year by year :smoking:

 

[DTOM420]

@DTOM420 -- how are the holes and plants going? Manage to defeat the rain and flooding?

I stalled out on the holes for a while but will start back on them shortly. Work got crazy for several months. We did get past the flooding although rivers and ponds are still at historic heights. The weather continues to be weird, though. No freezes at all which will make for LOADS of bugs this spring/summer if it doesn’t change soon. On the bright side, digging those giant holes is a lot more pleasant in the 50°’s and 60°’s than it was at 95°to 100°!

Thanks for asking!!