Asked November 15, 2013, 5:25 PM EST

Soil test #7B46E6. If I add Horse or Cow Manure (fresh or composted)this fall does that change the other recommendations? Is Horse or Cow Manure considered a Natural Organic Fertilizer? Can I purchase just Potassium to add to the garden? Thank you, Jo

Grand Traverse County Michigan

3 Responses

Compost or composted manure are adding organic matter. There are only tiny amounts of nutrients. Your soil needs organic matter. But manure or compost are not fertilizers.

This is a soil that need a lot of nutrients, organic matter and pH adjustment.

Your soil needs a great deal more than potassium. According to your test results, you have a sandy soil with very little organic matter. You want about 5% organic matter. You have 1.1 % currently. Your soil pH is have alkaline soil which is not good. You have 7.8 and want 6.5. That's about from here to the moon apart. Your soil requires nitrogen, phosphorus and potassium:

3-4 lb. 1.1 lb. 7.2 lb.
(nitrogen) (phosphorus) (potassium)
This is what you need of each, but these are fertilizers that are 100% pure of that nutrient. None exist. They all come in percentages. This is what you would use with traditional fertilizers for the season:

Nitrogen: 14-19 lb. 21-0-0 (ammonium sulfate) that will also lower your high pH
Phosphorus: 9 lb. bone meal
Potassium: 12 lb. 0-0-60

This is what you need for the entire growing season.
You will divide the fertilizers into three or four relatively equal applications like... one third before planting. One third six weeks later and the last third six weeks later. If you are using the 19 lb. nitrogen, add the last one-fourth of nitrogen six weeks later. You will have already applied all of the phosphorus and potassium. Repeat for three years and get another soil test to see what has improved (potassium, phosphorus and pH).

Once the garden is in, put the fertilizers in the aisles and not on the plants. The soil must be damp and them watered in.

If you are using organic fertilizers, these numbers will all different. Since I do not know what you can find in nitrogen, phosphorus or potassium, I cannot give you recommendations because I don't know what numbers are on the bags. But you really have to lower the high pH. The 21-0-0 will do that.

Thank you for all the great info. Are your suggested NPK amounts based on a 1000 square foot area? And yes I would like to go the organic route.
Thanks, Jo

Yes...1000 sq. ft. just like the recommendations on the test.

You will have to find organic alternatives for the N, P, and K and you may need to add sulfur if your N source does not acidify. That whoppingly high pH will block the uptake of most the added nutrients and whatever is available in your soil. Good luck!