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| Hi,
Are these two fertilizers OK for roses. Because of the Muriate of Potash, I believe, it has 28% Chloride. I have several other fertilizers I could use but have a 50 lb bag of this stuff which can be very water soluble or just used as a topdress. Thought maybe I could use it on Roses since the Urea makes the soil more acid. But I don't know if roses get Chloride toxicity. Any experience with this? Thank you for your help. Bob |
Follow-Up Postings:
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| Organic fertilizers, manure, and compost all release nitrogen in the form of urea, which is part of the natural nitrogen cycle. Any acidifying effect is caused by overuse of any N fertilizer, when the urea (or whatever form of N) converts to excess nitrate, and the nitrate leaches out of the soil with rain or irrigation. But a more immediate problem with excess N is the danger of poisoning the plants. Apply only 1 TB of urea per average-sized plant (6-10 sq. ft). It can be reapplied in 4 weeks for sandy soil or 6 weeks for heavy soil. MOP should also be applied only by the tablespoon, but if the soil contains clay or organic matter, it may already hold enough potassium for years to come. (One of the reasons to get a soil test.) The issue with chloride is the potential buildup of non-nutritive salts, mainly NaCl. I doubt that would become a problem in well-drained garden soil unless you use MOP excessively or combined with sodium nitrate. I would avoid using it in alkaline clay soils, especially in arid regions. But here, I apply MOP (in cheap 10-10-10) a couple of times a year. |
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- Posted by mike_rivers z5 MI (My Page) on Wed, Jun 20, 12 at 11:03
| I agree with what Michael wrote. "Chloride" sounds like bad stuff to people and that's probably the major reason why fertilizer makers use the old name, muriate of potash, for potassium chloride and why most rose fertilizers use the slightly more expensive potassium sulfate instead. Large scale users of fertilizers (i.e. farmers) use potassium chloride almost exclusively. Potassium chloride does have a higher salt index than potassium sulfate but this should be no problem with well-drained soils and proper applications. It's maybe worth noting that both potassium chloride and potassium sulfate are certified for organic crop production. |
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| Thanks for the responses michaelg and Mike Rivers, I must plead ignorance when it comes to roses. I left roses a few years ago and moved to other plants. I am now adding some Belinda's Dreams again. Your answers have been very inspiring and will result in me doing more research before I get started. Sorry I might be wrong (and please shed some light, if I miss this)but I always thought BASICALLY that Nitrogen moves through three basic stages if you start with urea. (and plaese excuse this long ramble but it does lead back to my initial question.)First it is broken down to ammonium which can be used by plants. Excessive ammonium can be converted to ammonia and it can evaporate. The ammonium, when the plant exchanges the ions during the absorption process exchanges an ion which causes the soil to be acid. Microorganisms further break the ammonium down to nitrates which can also be absorbed by the plants (and micro-organisms). If the nitrogen is not fixed or taken into the bodies of the microorganism it can be subject to denitrification and can also evaporate. Additional conversion can produce a water soluble version which can be leached. The nitrate version, through the ion exchange can result in a alkaline ion which can make the soil more alkaline. This is why it is perfered to have a fertilizer with a 40% Ammonia versus 60% nitrate ratio if the PH is to stay neutral. (Ammonia being a stronger producer on ions.) My question really asks about the effect of Urea in creating the right PH for roses. It is like relying on the Urea to convert to a slightly acid state and not being negated by the nitrate producing alkalinity state. But I guess that depends on the soil and buffer effect, etc. When you state the "excess nitrogen ...poisoning the plants". Do you mean the salts? What PPM of nitrogen will poison roses? Isn't nitrate poisoning possible through nitrate accumulation when the nitrates are above 5000 ppm? Wonder what the threshold is for roses? I try to keep the PPM for nitrogen at about 300 when applying most my plant formulas. Don't know about roses, however. I need your help to understand the concept of holding the potassium for years. In my environment it is the phosphorous that is held. The potassium leaches only second to the nitrogen. I did just find a comment in the presentation below that states that roses are one plant sensitive to Chloride, so I guess that is resolved. Thanks again for you informative answers, Bob |
Here is a link that might be useful: Don't get burned
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| Maybe I should leave the chemistry to mike_rivers, but, subject to correction, nitrogen evolves as follows: protein -> urea -> ammonia ->ammonium -> nitrite -> nitrate Organic sources contain protein, manufactured fertilizers one of the others. But no matter where you start in the sequence, you end up with nitrate. The only major effect on pH occurs if much excess N in any form is applied; then when the unused nitrate leaches out, it carries a (+) ion with it and lowers the pH. For this reason Miracid can acidify soil through a slight overdose of N, starting with urea, but the nitrate end product does the acidifying, and only when it leaves the scene. Roses happily accept ammonium. An excess of ammonium applied to the soil or the leaves can burn foliage. Roses also take up nitrate. An excess of nitrate causes dwarfing and abnormally dark green foliage. This is what I meant by poisoning the plants with excess N. Denitrification occurs when nitrate is in waterlogged soil. It isn't harmful beyond the waste of fixed N (which reverts to gaseous N). N can also be wasted as ammonia gas if urea or ammonium are not dissolved in the soil moisture. Really the only thing we need to worry about is ensuring a steady supply of available nitrogen while avoiding a large excess. "Holding potassium for years." Potassium, like other cations, bonds lightly to clay particles and organic matter so that it doesn't leach out, but plant roots can detach it. (Ammonium is another (+) ion. It will stay a few weeks until used or converted to nitrite.) Maybe 5 years ago, I saw a bulletin from the Arkansas ag extension announcing that some farmlands were running short of K for the first time ever--after having been cropped for well over a century without K fertilizer. However, sandy soils may need K on a regular basis. Again, I don't think you need to worry about salt buildup in Florida soils. It is a concern in container gardening, and in the West where irrigation water is salty and the soil is not flushed by rains. |
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| And if you want a simple, but well done, presentation on how Nitrogen affects soil PH" here is a very good video. See the link below. |
Here is a link that might be useful: Nitrogen and soil PH
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| For anyone wanting to learn more about nitrogen and how it works, here is an easy to understand video on the nitrogen cycle. |
Here is a link that might be useful: Nitrogen Cycle
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