Most soluble fertilizers (20-20-20, 15-30-15, 30-10-10, etc.) which are sold in garden centers have urea, ammonium phosphates and potassium nitrate as their major ingredients. 20-30-20 and 10-60-10 also have a lot of monopotassium phosphate (MKP). Over the long term, these products acidify the soils to which they are applied. However, some base-rich blends such as 15-5-15, 15-2-20, 15-0-15, 14-0-14, 13-2-13 and 12-2-14 have been developed for the hydroponics and greenhouse trades. They are dominated by nitrates of Ca, K and (in most cases) Mg. Where P is present, an acidic P carrier is essential to prevent precipitation of Ca-Mg phosphates. Urea phosphate (made of urea and phosphoric acid) is most common; 12-2-14 uses MKP. The P-containing products may acidify the soil over a short term, but their abundant basic cations ultimately put the soil pH on an upward trend. I have had satisfying results from 15-5-15, 15-2-20 and 14-0-14 (which are frequently available in at least one specialty outlet near Victoria). Given the strongly acidic nature of most soils in humid parts of B.C., these fertilizers should be more widely used. -Tony
interesting thread start Tony, I am curious to see where it goes. For my .02 I would say this; Do you feel that even with the minimal amounts of actual nutrient being applied with a soluble fertilizer, is pH action and cation exchange a major factor in an outdoor landscape? I can understand the concern in a closed system with limited moisture (aka reservoir).
Hi Tony You say that you have had good results with a listed number of fertilizer. just a few Questions :) What PH did you start with and what nutrient level 1 What are you growing 2 closed or open enviroment 3 15-5-15 does that not = 5-1-5 ?( can't rember the formula of the top of head) 4 What type of micro or macro nutrients are added ? In hydro systems (or closed) the "food does not leave the system but gets flushed and refreshed an a regular basis. In the landscape enviro this is not true ( in my opinion) Looks like we are going to the moon or is this just general :0 regards doug
I've used these products on an outdoor garden, and indoor potted plants. I don't have a hydroponics system. Soils are sandy in my front yard (the sand was added), gumbo in the back. They are strongly acidic (pH around 5.2), unless limed. The most impressive results I've had were with peony and rose on sandy soil. The 15-2-20 coaxed more growth and better bloom from these plants than 20-20-20 or 15-30-15 did. This year I got excellent results from using 15-5-15 on cosmos, marigold and nasturtium, also on sand. The abundance of soluble calcium in these base-rich fertilizers makes a good crumb structure easier to maintain in clay, but the urea/ammonium phosphate-rich products produce more vigorous growth. All of the fertilizers mentioned above have the usual group of micronutrients -- boron, copper, iron, manganese, molybdenum and zinc -- except for the 20-30-20 and 10-60-10, which only add iron, manganese and zinc. -Tony
It can be, if the soil has a very low cation exchange capacity. Plants growing on sand would likely benefit from soluble basic fertilizers, as would gardens supported by Oxisols (common in the humid tropics). -Tony
That's certainly possible, but at least one manufacturer has provided detailed information about element concentration and electrical conductivity at various solution strengths. At http://www.scottsprohort.com/products/water_soluble_fertilizers/peters_formulas.cfm you can click the Tech Sheet icon for each product. -Tony
Is the soil to which all this material is being applied being repeatedly sampled and tested, to keep track of how it is being affected?
No ... my goal is to see if the base-rich nitrate fertilizers have any advantages for plant growth over the more common urea + ammonium compounds in the outdoor garden. -Tony
