Sand anybody?

[SlipperFan]

So, how about if I go to Lake Michigan and scoop up some of the sand from the dunes?

Or pick out some sand from the bottom of the little river that goes through the back of our property?

 

[Rick]

I carried the experiment one step further, which overlaps with my sphag/basket potting method I'm trying.

I took a 4 inch basket with a recently potted roth seedling in it (which has grown about 20% since potting up).

The media makeup in this basket is:
1) at least 80% by volume sphagnum
2) about 20% hydroton pellets
3) about 1heaping tablespoon of white play sand
4) about 1/4 tsp of "Cichlid sand" (an aquarium buffering sand).

Using my misting wand I applied my irrigation water until I collected about 100 ml of water dripping from the bottom of the basket.
Irrigation water chemsitry:
1) pH ~ 7.5
2) conductivity about 40 useimens/cm
3) hardness ~ 20
4) alkalinity ~10

My irrigation water is about a 10:1 mix of lab grade RO water and my household well water.

The chemistry of the water dripping out of the basket:
1) pH = 6.2
2) conductivity = 300
3) hardness = 60
4) alkalinity = 19

Slight yellow color.

These are numbers that look optimal for nutrient/mineral uptake by orchids, and its apparent that the white play sand (or the dash of Cichlid sand) is not raising the pH to unsafe levels.

 

[Rick]

So, how about if I go to Lake Michigan and scoop up some of the sand from the dunes?

Or pick out some sand from the bottom of the little river that goes through the back of our property?

Probably wouldn't hurt:wink:

 

[gonewild]

So, how about if I go to Lake Michigan and scoop up some of the sand from the dunes?

Probably a good source.

Or pick out some sand from the bottom of the little river that goes through the back of our property?

Probably not a good source.

The dune sand would be very clean and free of organic matter.
The river sand may contain undesirable micro organisms and also fine silt.

 

[gonewild]

Using my misting wand I applied my irrigation water until I collected about 100 ml of water dripping from the bottom of the basket.
Irrigation water chemsitry:

Another good comparison would be to collect the free water in the basket and test that. This would allow you to analyze the water that the roots sit in contact with and be less influenced by the fresh irrigation water.
About midpoint between waterings tilt the basket at an angle and some water should run out of the bottom. Collect from several different baskets and test that sample.

 

[Rick]

Probably not a good source.

The dune sand would be very clean and free of organic matter.
The river sand may contain undesirable micro organisms and also fine silt.

Depends where you are on Lake Michigan.

It may not be so great if you are down in the Chicago/Whiting/Gary end where all the steel mills are.

In either case it may not be a bad idea to boil it or wash/soak it in chlorinated tap water.

 

[SlipperFan]

Thanks, guys! I'm a long way from Chicago. Next time I'm at Lake Michigan, I'll take a scoop and a sack.

 

[Rick]

Another good comparison would be to collect the free water in the basket and test that. This would allow you to analyze the water that the roots sit in contact with and be less influenced by the fresh irrigation water.
About midpoint between waterings tilt the basket at an angle and some water should run out of the bottom. Collect from several different baskets and test that sample.

Yup thought about that.

Unfortunately with the sphagnum moss acting like a sponge, it really doesn't hold significant interstitial (free) water. I might be able to squeeze a bit out. I also tried not to bias too much by "flushing" by applying water fairly slowly, and grabbing the first flush (rather than letting it dribble out for a while before starting collection). Figuring that this first flush would have been a mixture of old/equilibrated water and new water. Lots of ways to standardize the proceedure.

I also need to correct the incoming water chemistry. (Made a fresh and precise batch and took it to the lab).

pH = 7.04
conductivity = 115
Hardness = 51.2
alk = 33.

 

[Lance Birk]

If you want the benefits of organic and elemental nutrients use the river sand. Plants will love it and will respond noticeably.

If you want silica sand without nutrients use the sand from the dunes.

 

[cnycharles]

if you use the river sand, should it be baked to get rid of any unwanted micro-organisms?

 

[Rick]

if you use the river sand, should it be baked to get rid of any unwanted micro-organisms?

The world is full of micro-organisms so I usually feel its futile to achieve sterility, but you never know

 

[gonewild]

Yeah you don't need to try to get rid of all the organisms.
Id you are using washed river sand like what is sold to mix with plaster or bagged sand there is no need to wash or sterlize it.

But if you are using sand that you collect I would suggest being careful about not sterilizing the sand. Because the sand is from a river it surely contains a high volume of fungi, nematodes, and probably even root eating insect larvae.
Sand from dunes probably never had much terrestrial fauna growing in it and commercial river sand is usually dug from deep in the riverbeds where all organic matter has been gone for years and years.

 

[gonewild]

If you want the benefits of organic and elemental nutrients use the river sand. Plants will love it and will respond noticeably.

If you want silica sand without nutrients use the sand from the dunes.

Some rivers cut through limestone mountains and some cut through volcanic mountains.
Are you considering all river sand as equal?
Eastern USA vs Western USA?

 

[Rick]

Some rivers cut through limestone mountains and some cut through volcanic mountains.
Are you considering all river sand as equal?
Eastern USA vs Western USA?

It's hard to generalize even at the level of east vs west of the Mississippi. Even in TN we have at least a dozen different geologies with sandstones, limestones of all kinds, and granitic areas. But TN could be special, it has more species of crayfish, freshwater fish, and freshwater mussels than any other state in the union reflecting the diversity of aquatic habitats in the state.

 

[Lance Birk]

"Sand' does not come from limestone mountains.

If you anticipate gaining the benefits of using sand in your potting mix use the 'washed river sand' like I first described in my grower's manual from 1984.

 

[smartie2000]

i also have decided to use sand as soon as I get to repot The results I have seen on the forum has shown.

I don't know if this is worth mentioning, my Cypripedium parviflorum growing in perhaps 50-70% sand had no root rot at all.

 

[Rick]

i also have decided to use sand as soon as I get to repot The results I have seen on the forum has shown.

I don't know if this is worth mentioning, my Cypripedium parviflorum growing in perhaps 50-70% sand had no root rot at all.

You don't have to wait for repotting, you could top dress now, and most of it will work its way into the matrix with shaking and watering.

One of the Phal experts in our society mentioned that it was a great life extender of bark and moss substrates (which I mentioned in the first post of this thread).

 

[Rick]

"Sand' does not come from limestone mountains.

If you anticipate gaining the benefits of using sand in your potting mix use the 'washed river sand' like I first described in my grower's manual from 1984.

The creeks around here definitely have some sand in them, but you also trip over limestone boulders to get to the creeks in the first place.

Granted the creeks in the "limestone hills" around here more likely than not have solid bedrock bottoms with very little sand or gravel in them at all. As the grade declines you find more areas of cobble / gravel, and the big sand deposits are at the lowest gradient streams.

Since limestone is so soft, the finer particulates are composed mostly of hard silicates, which is probably pretty universal in "sand" from one river to the next.

 

[Rick]

Some of the numbers on my irrigation seemed off compared to some older records I had for my well water, so I tried it again.

I pushed the dilution rate closer to 10:1 and got:

pH = 6.86
conductivity = 61
hardness = 25.6
alkalinity = 25

Here's a new one PO4 (orthophosphate) 1.25ppm.

Given something close to the 10:1 dilution rate that means that the conductivity of my undiluted well water is presently close to 700 useimens. Which is about 2X higher than I've ever recorded for it.

The phosphate is a great bonus for regular watering, but once again with a 10:1 dilution that indicates I have 10+ ppm of phosphate in my well water! About 3X any historical amount I've measured in the past.

 

[gonewild]

Is you well deep or shallow?
Where does the water column stand in the well, is it deeper than before?
Maybe you have more or less water in the formation so the mineral dilution is now different. Or could indicate that there is some new water source entering your well. When you see the chemistry of well water change it is wisse to look for possible contamination.