When it comes to using cow manure, this is what I do to prepare my mix, and I suggest you do the the same thing:

1) Lay out a large tarp, plastic sheeting, or my personal favorite: tin roofing sheets.

2) Collect your dirt. I use native soil, but I live in a rich region. Depending where you live, you may want to buy soil from your local hardware/gardening center.

3) Put your dirt on top of the tarp or plastic sheeting, and SPREAD IT OUT EVENLY. Don't just put into a large pile, or it defeats the entire process of what we are doing.

4) Collect your manure. Make SURE this manure is atleast 3 months or older. You'll be able to tell this by prying it open with a stick and making sure it is completely LIGHT BROWN throughout every layer, including the top and the bottom. It should essentially look like an extremely compressed clump of dead brown grass, which is exactly what it is. If it is dark brown throughout any layer, don't use it, as the manure is still "burning" and considered too hot to use for young plants.

5) Collect your manure and CRUSH it up thoroughly. I personally put the manure into a 5 gallon bucket, and use a small hand-shovel or spade to break it up until each clump is less than 1/4 inch in size. It's important to have this broken up as much as possible so that you get an even distribution in your mix.

6) Take your crushed up manure and pour it on top of your soil, remembering to maintain a 1/4 ratio. Make sure the manure and soil is tossed and mixed as much as possible. I use a ho and a square-head shovel for this, turning the entire pile over 10+ times on all sides.

7) This is the easiest, but most important step: LET IT COOK. Given you have a few decent days a week of sunlight, this mix will "cook" and decompose under the sun. Allow this pile too cook for atleast 3 months, remembering to turn this pile over ONCE A WEEK to ensure that all of the layers of dirt and manure cook evenly.

You should start your entire process 3+ months before planting. Really, 3-6 months is ideal, and some people will even go to the extent of cooking ot for over a year. Although ideal, that's a bit excessive and not really necessary unless the manure is dark/fresh. I honestly forget some years and make my mix about 6-8 weeks before planting, and I can tell you that I have never had a problem with that. But then again, I look for very old piles of manure, and keep my ratio down more than others. Hoipe this helps anyone and I encourage all growers give it a try.

That's it. It's a great and simple mix for beginners, and veteran growers of 60+ years experience still use it to this day on everything that grows under the sun, especially including marijuana! Try it this year and you might just find out you've been wasting far too much money on chemicals and store-purchased fertilizers.