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Archived Questions
Q: I'm interested in a recipe for a universal plant fertilizer that could be prepared using commercially available chemicals.
The Expert: I'm not exactly sure what you are asking. There really isn't a recipe for a universal plant fertilizer. Presently, there are many different fertilizers on the market because there are specific applications where one is better than another.
For a good "all around" fertilizer, I would use 8-8-8 or 10-10-10. We call this a "balanced" fertilizer because it has all three major nutrients (nitrogen, phosphorus and potassium) in equal proportions. This is not particularly good as a lawn fertilizer, however. A good lawn fertilizer would have a higher percentage of nitrogen than phosphorus and potassium.
As for using commercially available chemicals, you can buy different fertilizer materials and mix them in different ratios, depending on what analysis you want. In agriculture we do this all the time. It is called custom blending. In this case we are making specific fertilizer analyses for specific fields and crops. We match crop and soil needs on a field by field basis with these custom blends. The fertilizer materials we use in these blends are commercially available, but not often seen in lawn and garden stores. You would probably need to go to a farm center to buy these "straight" goods. The most common ingredients to make custom fertilizer blends are urea nitrogen, diammonium or monoammonium phosphate as the phosphorus source and muriate of potash for the potassium source. There are several other sources but not all are available to the general public. How much of each you would use depends on what analysis you want.
By now I think you can see that this is not a real cut and dried easy process. That is why fertilizers sold to the general public are pre-blended and many different blends are available. The intent is to have different fertilizers available for different intended purposes. Hope this explanation helps.
Q: Do fertilizers have a pH level? And how does this affect plant growth?
The Expert: Yes, fertilizers do have unique pH levels. In the short term, however, the pH of fertilizers doesn't usually affect plant growth. When looking at it from a field basis, where we assume an acre of topsoil weighs about 2 million pounds, we aren't adding enough fertilizer to directly influence the crop. Also, soils are so well buffered that any pH affect from the fertilizer is short lived. Some people claim that an "acid fertilizer" will help release soil nutrients in alkaline soils, but from my experience, this is a temporary effect that has no long-term benefits.
As for soil pH and fertilizers, however, some fertilizers are more acid forming in the soil. All nitrogen and sulfur fertilizers will cause soil to become more acidic over time. On acidic soils, we need to follow this acidification process and apply lime when necessary. On alkaline soils, these reactions still take place. But again, soils are so highly buffered that a pH shift is rarely noticeable.
Q: I had a healthy stand of pacasandra until last summer. A well-defined section turned brown like something was poured on it. This year it's coming back, but the growth is short and sparse. Could this have been heat or drought related? I'm in Georgia. It grows in the shade, except about an hour a day.
The Expert: Since your problem is in a well-defined area, I doubt that it's heat or drought related. If in doubt, however, give it a good watering once a week and see how it responds. Also, you can add a little balanced N-P-K fertilizer to see if that helps. Other than that, I don't know what to tell you. Sorry I can't be of more help.
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