One would think this could be answered using the search function, but I'm really having trouble finding anything that fits with what I'm doing. I have several citrus trees, mostly eureka lemon and one orange (can't recall the exact type). All of them are planted in 12 inch pots using the 4:1 CHC/peat moss recipe recommended by Millet. What I have been doing in the past is watering about every 2 weeks and adding Miracle Gro for houseplants. This is a 24-8-16 fertilizer with trace minerals. I've been following the instructions on the box for indoor plants which is 1/2 teaspoon for every gallon of water. However, I'm starting to think that may not be quite enough. Everything I've read recently in the forums say that the trees are a "heavy feeder." The indoor plant specification is the lowest of them all. Outdoor plants call for 1 tablespoon per gallon. What I've been considering doing is adding Osomocote 19-6-12 (no trace minerals) to the top portion of the growth medium in addition to adding the Miracle Gro to each watering. From what I've gathered, this type of system isn't uncommon. I just really don't want to accidently overdo it. Sorry to be such a pain, but with my limited knowledge, this raises a number of questions for me.... 1. How much of each? 2. How often should I renew the Osomocote? 3. Is the trace minerals in the miracle gro alone going to be enough? 4. Should I also add epsom salts to the regime? How often/ how much? 5. Maybe I'm way off base here? :) I realize this isn't something totally cut and dry here. However, there is no question even an educated guess from some of the experts here is certainly better than my non-educated guess. Thanks in advance, this forum rocks. Nearly forgot to mention the trace mineral content... B - .02% Cu - .07% Fe - .15% Mn - .05% Mo - .0005% Zn - .06%

Matt, I'm interested in all the same questions. If fact I got on this forum this morning to find out some of the same questions. Very excited to hear the feedback. Thanks for posting these questions.

If you continue to use the MG, I would increase the amount to 1 Tbs/gal. I use the same Osmocote, but I add a trace mineral mix. The amount of Osmocote is dependent on the container size, but I apply it about every 4 months. Since your trace minerals do not include Mg, I would add Epsom salt to your routine.

Skeeterbug, Since you use the Osmocote slow release fertilizer with no trace minerals, how often do you add your trace mineral mix & how much do you add to a 12 inch pot. Do you just sprinkle the powder on top of the soil & water it in or do you mix it with water first. Also how often do you add epsom salt in your plant?

Matt-- If you increase the MG to 1 Tbs, I would not use Osmocote. It would be best to use one or the other. eulowife-- I just apply the trace mineral mix to the surface of the container. I apply about a 1/4 tsp to 1 gal pots once a year. The mix I have is something like "Essential Element Mix" from Southern Agricultural Chemicals. I get it at an Ace Hardware. This mix also has Mg, but I still add about a Tbs of Epsom salt to a 5 gal bucket of water a couple times a yr. We have a lot of rain here most years (about 5 ft) and our sandy soil does not hold minerals very well, so a little extra Mg is not likely to cause any salt problems.

According to research at the University of Oklahoma, by Dr. Carl Whitcomb, the most successful method of growing nursery (containerized) fruit bearing trees, and containerized non-fruit bearing trees, is by a nutrition program that utilizes both a slow release fertilizer, and a water soluble fertilizer. Research has shown the addition of a slow release fertilizer, such as Osmocote, along with the regular feedings from water soluble fertilizers, lessens the nutritional feast and famine cycle that occurs when only water soluble fertilizers are used, especially during the faster growing seasons of the spring and summer months. - Millet

Excellent, thank you very much for the info guys. Stupid question -- does 250PPM once a month refer to the sum of the NPK?

250 ppm (actually 250 to 300 ppm is the N concentration recommended by citrus reseachers for routine watering) would be slightly over 1 g per liter of 24-x-x.

Matt, no question is stupid, actually you ask a great question. Many people do not understand parts per million (PPM). By convention, when parts per million of a fertilizer is calculated, it is customary only to use the element nitrogen (N) in the formula as the referenced element. Therefore, when one wishes to calculate 250 PPM of the formula 24-8-16, only the 24% nitrogen is calculated. By definition 1 ml per L = 1 PPM. Here is a formula to determine PPM: When 1 ounce (30ml) of fertilizer is added in 100 gallons (378 L) of water, this is equivalent to 75-PPM. In using the number 75, it is possible to calculate PPM for any fertilizer. Step 1: Multiply the percentage of nitrogen in the fertilizer by 75. Step 2: Divide the result from Step 1 into the desired PPM of nitrogen. Example using your formula 24-8-16, 250 PPM will be calculated. Step 1: 75 X .24 N = 18 PPM N Step 2: 250 PPM Divided by 18 PPM N = 13.89 Ounces fertilizer per 100 gal. water Then divide by 100 to get PPM per one gallon of water. 13.98 ounces fertilizer divided by 100 gal. water = .1389 ounces per 1 gallon. Therefore if you add .1389 ounces (3.8 grams) in one gallon of water you have 250 PPM nitrogen. NOTE: There are 28 grams per ounce. Practice the formula a little, and it will become second nature to you. Great question, I'm sure your question will help a lot of people understand PPM and how to calculate it. - Millet

My calculation is a little more straight foreward. There are 1000 g in a liter. 1,000,000 mg in a liter--therefore 250 mg in a liter is 250 ppm. 24% of 1 g of 24-x-x is 240 mg N. So as I said, a little over 1 g per liter of 24-x-x is 250 ppm. My guess is that your calculation included the other elements into the calculation N+P+K, but the 250 to 300 ppm recommendation refers only to N. Millet's calculation is correct for 1 gallon.