Types of calcium for best bloom formation
Calcium is needed for best bloom formation, and potassium for bigger blooms. My soil is limestone/dolomitic clay, yet my soil test came back barely adequate in calcium, due to calcium-tie-up at high pH.
In hydroponic experiment with fertilizers, the biggest root growth was through high potassium, some phosphorus, and nitrogen through calcium nitrate. If the soil is sandy, more nitrogen is needed through leaching, and calcium nitrate would supply both calcium and nitrogen.
I checked many sites on gypsum whether or not it lowers soil pH. Some sites says "yes", some sites say "no". So I tested it: I put more gypsum (calcium suifate) on some rose bushes before our week-long rain.
The dark-green ones that like alkaline soil: French Romanticas & Meilland DIDN'T LIKE the excess gypsum: leaves became thinner, and droopy. It's very much like the time I put too much sulfur on Sweet Promise ... leaves became thinner, more droopy.
Roses with musk or multiflora parentage that prefer acidic soil, LIKE gypsum. Excellenz von Schubert, a hybrid musk, does well with added gypsum, so does Annie L. McDowell.
U of CA Extension chart in the below link listed 1 ton of gypsum as equivalent to 5.38 ton of sulfur. It also listed 1.09 ton of Ferric Sulfate as equivalent to 5.85 ton of sulfur. See link below:
If your soil is acidic, hold off the gypsum. That stuff is great in California, where the soil & water is alkaline ... but there are better sources of Calcium for acidic soil, according to the info. from EarthCo. booklet, provided FREE with the $20 soil test (gives soil pH, calcium, magnesium, phosphorus, potassium, and organic matter).
Gypsum provides 22% calcium, 17% sulfur, with salt index of 8.1, used to de-salt sodic soil, also to neutralize bicarbonates in alkaline tap water.
Dolomitic Limestone provides 25% calcium and 10% magnesium, salt index 0.8, sandy soil lacks magnesium
Calcitic limestone provides 36% calcium when the rain water (pH 5.6) breaks it down, low salt index 4.7
Colloidal rock phosphate provides 19% calcium and 18% phosphate. Best for acidic soil, cannot be utilized at pH over 7.
Hard rock phosphate provides 48% calcium and 30% phosphate, cannot be utilized at pH over 7.
Bone meal has 11% phosphorus and 24% calcium. Bone meal cannot be utilized if the pH is over 7.
Superphosphate provides 20% calcium, 12% sulfur, and 20% phosphorus, low salt index 7.8
Wood ashes provides 20% calcium, 2% phosphorus, 7% potassium, magnesium, and all trace elements. CAUTION: Wood ash is very alkaline, pH over 10, will burn roots if applied directly to plants.
Wood ash is great for acidic clay, where my Mom put wood ash on top of a thick layer of leaves. Snow and rain (pH 5.6) counteracts the alkalinity of wood ash. Below is a bouquet picked recently in 90 degrees humid weather. I use both gypsum and sulfate of potash for best blooms:
Here is a link that might be useful: on-line-soil test at EarthCo. for calcium & soil pH & others
This post was edited by Strawberryhill on Mon, Nov 18, 13 at 10:31