Our small farm in Colorado includes in-ground seasonal production from mid-April through September and year-round indoor hydroponic production.  If you are growing in-ground in Colorado, planning on doing so, or just thinking about it, and you want some information about soil amendments, here is what we do.  Before we get to our list, we'll share a few details to give you more context.

First, we operate a small, organic, local farm.  We follow organic practices as best as possible and scrutinize our inputs to production, including soil amendments, seed quality, water quality, and pesticide control. These are done to ensure we grow an organic product free from all or as many pesticides and synthetic materials as possible.  We don't classify our equipment for growing and harvesting as an input.  It's more like a facilitator, but still we scrutinize the type of equipment just as much as we do the inputs.

Second, we generally stick to using warm-season crops that have done well for us outdoors.  Those include vegetables like carrots, parsnips, radishes, cucumbers, zucchini and squashes.  Our cool season crops like lettuces, other leafy greens and broccoli have not done well for us outdoors due to the heat we get in the height of summer in Colorado, so we stick to growing those crops indoors hydroponically.

Third, we grow on generally sandy loam soil that drains well.  You can find out more about your soil type where you live from the web soil survey by the U.S. Dept of Agriculture.  You can drill down to a very specific geographic area like we did with the screenshot image. It shows the location of our in-ground growing area and the soil type information. Knowing your soil type is very important so you know what additional amendments are needed and in what quantities to achieve your growing goals.

For us, the our main soil amendments that have worked well include the following:

  1. Organic material.  Our main source of fertilizer is composted horse manure from a ranch located next door to us.  This is a small working ranch with horse stables for local owners and grass-fed cows that free-range on parts of the 1200 acre ranch.  We know the owners and ranch managers and know their inputs to what they feed the horses, so are comfortable in the quality of the manure we get from them.  We also use composted chicken droppings from our own chickens  and our own composted kitchen scraps, but neither amounts to much.  The horse manure provides most of our organic material.
  2. Colloidal Phosphate.  This is a natural source of phosphorus and calcium. It is comprised of the bony structures of prehistoric marine creatures.  We apply it about every 5 years.
  3. Greensand.  This is a mineral called glauconite, which is found on the ocean floor and mined for use as an organic fertilizer and soil conditioner. We apply it about every 5 years.

A short list, and that's the way we like it because it makes growing easy. Our crops do very well with the above soil amendments and we don't see the need to do anything further. The horse manure is our main amendment and we use quite a bit of it.   The nice thing for us with the manure is that it is free, abundantly available and easy for us to pick up in our tractor and trailer and bring to our farm.  If you can obtain horse manure, that may be all you need to meet your growing goals.