raised bed mix that holds moisture

[jbclem]

My regular ground soil is sandy silt/silty sand and water drains through it fairly quickly. I'm using it in my raised beds and I need to add something to it so it will hold more moisture...for growing upland rice that needs as much moisture as corn. It's too expensive to buy bags of commercial mixes, and I'd like to amend what I've got. Any suggestions?

[maxjohnson]

Compost. Be that leaves, mushroom, or composted manure.

Growing in the ground in Florida sandy soil, no matter how much I buy fertilizer, they just get washed away quickly. It was the discovery of compost that made healthy soil happen. Mulching is also important in hot climate with dry soil, just remember rule of thumb to not mix fresh woodchips into the soil otherwise the wood will bind up the nitrogen until it is broken down. If you have a pickup truck then it'll be much easier to buy compost by the cubic meter from local supplier, but you have to test a small sample and grow something in it first to see its good quality and no contaminated. Some municipals may have free mulch and or compost and give details from their website, ymmv.

[jbclem]

When you mix compost with your sandy soil, how much compost do you add per square foot of soil. I have some compost piles, but I'm not sure I'll have enough...although I'm starting out with a raised box that's about 15 sq ft. Since I'm growing organically, I can't just go out and buy compost or horse manure. Not many people make organic compost (like I do ) and horse manure is going to be full of pesticides/herbicides that are sprayed on the hay that is fed to the horses.

Have you tried adding peat moss to the sandy Florida soil, I wonder how that would work. Perhaps combined with compost.

[MissS]

Peat moss is a great addition to sandy soil. It holds a lot of moisture but also a lot of air. Do be aware that it does take some time to initially get it wet so you may want to pre-moisten it before adding it to your beds.

[Cole_Robbie]

Vermiculite also holds moisture. You can often find it sold as insulation.

[PlainJane]

I use coco coir in my raised bed mix in lieu of peat. Does well!

[bower3]

I would just add as much of your compost as you can, and see what you think of the results, maybe add more the following year.
I've never worked with sandy soil. But I have to say that composted horse manure is the best amendment I've seen for moisture retention. I grow organically too, and I haven't had a problem with my local source of manure. But I'm leaving it to rot for an extra summer before I use it. I also take some and layer into my compost piles to heat them up. Those slow compost piles take a full year anyway before they'll be used.
I know it's not as ideal as having your own horses or an organic pony source, but time does break down the contaminants. Herbicide I know is the worst, and lingers, but so far I haven't had that problem, which turns up really clearly in tomatoes.
Peat will certainly contribute to moisture retention, although adding no nutrients.

I'm really interested in grain growing, and tried some different wheats but not the upland rice as yet. Please let us know how it does for you.

[maxjohnson]

When you mix compost with your sandy soil, how much compost do you add per square foot of soil. I have some compost piles, but I'm not sure I'll have enough...although I'm starting out with a raised box that's about 15 sq ft. Since I'm growing organically, I can't just go out and buy compost or horse manure. Not many people make organic compost (like I do ) and horse manure is going to be full of pesticides/herbicides that are sprayed on the hay that is fed to the horses.

Have you tried adding peat moss to the sandy Florida soil, I wonder how that would work. Perhaps combined with compost.

Honestly I never calculate how much compost I add in raised bed since they drain well. I'm only concern of too much compost in containers which if have poor drainage can cause anaerobic activity.

As for peat moss, this year I dumped two years old potting mix from my Earthbox containers into my raised bed. They do hold moisture well, but if you let them dry completely they become hydrophobic and water can't penetrate the top layer. So say you neglect to water your raised bed and the peat moss below become very dry, even if you think you water well each day it may not be enough to moisten the layer beneath. So if this is fresh peat moss you are adding, I would mix it with the soil and or compost and water it a lot while mixing. The other thing is fresh peat moss don't have nutrients, and potting mix barely any, so fertilizer is a must imo.

Mulching was key in Florida. These days I try to top up my raised beds with a 2inch layer of compost each year which is considered a mulch layer too.

I actually used vermiculite once and stopped because I thought it was holding too much water in containers, maybe that helps I can't say by experience.

MIgardener have this concept called core gardening, I never tried it myself since I try to not till my soil. Here he is adding straw on the inside of his beds. I have done strawbale gardening and one thing I liked it about it was how well the bale holds water so I didn't have to water them daily. I'm guessing for this method if you don't have or don't want to use straw, maybe dried grass clippings or vegetations could work.

[zeuspaul]

Peat may be among the cheapest alternatives. Compost of course, Special Kitty Natural Clay Cat Litter, Fragrance Free from Walmart, Ground Cover bark from HD or Lowes depending on the batch. You have to inspect the contents first. Some batches are mostly wood shavings, you want the bags that actually contain bark nuggets. The last bags I purchased looked more like peat moss, probably came from the bottom of the pile. AutoZone floor dry (granular diatomaceous earth) good for moisture retention but a little pricey.

[jbclem]

I've added peat moss, moistened, to my first 15 sq ft raised bed . I filled (4) 18 qt dishpan containers with peat moss, and mixed it into 8-12" of the sandy soil. It looks much better and if I have enough I'll also put about 2 inches of compost as a top layer/mulch. I'll try to attach a photo that shows the original soil and the peat moss mix...this was taken before I finished the entire bed so you can see the difference.

P1230150.JPG

I would also have added mini bark (or ground cover bark) to the mix if it was available, but for some reason it hasn't been available at the box stores (here in S. Calif) for many years. Lowes has some junk called Pathway Ground Cover, but it's just large pieces pf shredded bark and mold.

[karstopography]

Hardwood Leaves and conifer needles are wonderful if you can get them in quantity, I rake them up and they are a free fix. They have to be incorporated into the soil and aren’t an instant solution, they need some breaking down over time. Dark reed sedge peat is an instant fix and in my experience far superior to sphagnum moss derived peat for how it handles moisture, but the dark sedge peat is harder to find and costs more.

I’m leery of anything bagged or bulk compost these days that comes from anywhere where horses or cows are involved. Aminopyralids are widely used, even in dairy cow feed streams(look it up if you don’t believe me, no restrictions in US with grazon for dairy cows), and they wreck tomato gardens coast to coast. Grass clippings can be suspect as well as lawn services use broadleaf herbicides. You can’t be too careful with aminopyralids, this stuff lasts a long time, doesn’t degrade in hot compost piles or ruminant guts, and is devastating to tomatoes in minuscule amounts.