Whatever dosage you choose I think it's far more important in the manner the ferts are given to the plants opposed to the amount, that's why I only foiler feed my plants. It gives you a LOT more control over what the plant intake is because the intake is almost immediate opposed to a LONG slow intake by the roots when you add ferts to the soil. Wouldn't you like to say that 85% of the ferts you give your young plant was absorbed in the first couple of hours? Plus your not wasting money on your ferts by washing them out of the pots when foiler feeding. I use a 12-9-6 until they start flowering and after flowering it's 9-18-9. You can use just about any powdered fert, by adding water and a wetting agent. I use water directly from a large fish tank and throw in a tablespoon of liquid detergent that contains polysorbate 80. Some guys go as high as 30 on the NPK scale which is fine for soil feeding because most of the fert isn't really used by the plants anyway so although you are loading up the soil with ferts the plant is probably only taking in a 3rd of those ferts. So a 15-30-15 mix is probably only giving the plants a 3-10-3 intake. I also foiler feed them with worm tea, a shot of cal/mag, and a few drops of superthrive every 4th feeding. If your not familiar with foiler feeding it's worth the research. I'll go ahead and post one of the many articles I've read on the topic for review in case you can't find it with the search function.
FOLIAR FEEDING
Foliar feeding is the entry of small amounts of liquid fertilizer through the surface of plant shoots. This allows for rapid nutrient utilization by the plant, and also provides the applicator the ability to blend the fertilizer with other products, such as pesticides and micronutrients. Current formulations of liquid fertilizers are believed to penetrate mostly the transcuticular pores on foliage, which are open virtually all the time compared to stomata. Nutrients also enter stomata, but these often are closed due to environmental stresses and darkness. Also, the majority of the stomata are located underneath leaves, away from fertilizer spray patterns. Drawbacks to foliar feeding include the inability to apply large amounts of N, phosphorous (P) and potassium (K) without potentially burning the foliage. Therefore, frequent applications at a low volume are required to maintain consistent color and plant growth.
FOLIAR ABSORPTION
Many products claim to be true foliar fertilizers that can solve most fertility problems. However, the majority of these products lack published research to substantiate these statements. A primary concern is whether you are applying a true foliar-absorbed fertilizer. Research on banana plants determined whether foliar applications of urea were absorbed through foliage or washed off and absorbed through roots. Up to 65 percent of the foliar-applied urea was absorbed within 25 minutes, with the majority being absorbed by the lower (or younger) surface of the foliage — where the greatest number of stomata exist. Similar findings were reported in coffee, cacao and McIntosh apple. The lower leaf surfaces and younger leaves rapidly absorbed urea from foliar applications as compared to older leaves and upper leaf surfaces. Complete absorption of the urea occurred in coffee and cacao in less than 24 hours and in banana by 30 hours. The absorption of urea by the lower surface of younger McIntosh apple leaves was as high as 85 percent in a two-hour absorption period, compared to the lower leaf surface of older leaves.
Many foliar applied products also contain “hidden” ingredients, such as iron, not specified on the label. So while you may be satisfied with the results, you may not realize which ingredient, specifically, is providing this response. One way to identify it is to know exactly which elements can be absorbed and moved through the plant. Mobile elements such as N, magnesium and sulfur are transported through phloem tissue in leaves. Meanwhile, immobile elements such as calcium and boron will not move through the phloem, thus, would not be as effective if applied as a foliar fertilizer.
Previous research in McIntosh apple focused on parameters hindering foliar urea uptake. These included existing N levels in the foliage, pH of the spray, temperature and the influence of wetting agents. High existing nitrogen levels in the foliage and low temperatures (~21°C compared to 32°C) promoted best absorption. Also, incorporating a wetting agent into the spray (Tween 80 and Tween 20) approximately doubled the percent of urea absorbed, compared to a pure water solution.
Most research indicates that with urea, for instance, liquid and dry (granular) formulations produce little differences in turf growth and quality. However, previous research with urea noted foliar feeding accounted for 95 percent of plant use compared to approximately 10 percent use from soil applications. In an attempt to address efficacy questions, studies compared fluid and foliar nutrition programs to conventional programs (conventional programs designed by select golf course superintendents in the state of Nebraska) on Providence creeping bentgrass. Fluid and foliar programs were comparable to the conventional programs in terms of color and density while incorporating 25 to 80 percent less N. Furthermore, it was suggested foliar fertilizers should not replace conventional fertilizer programs (liquids and water-soluble controlled-release granular fertilizers). However, “true” foliar fertilizers can increase the growth and vigor in turf under high maintenance, especially under stresses such as increased heat. Also, with the increased attention placed on N and phosphorous leaching, liquid fertilization could be very beneficial. The low input required by foliar applications could pose a smaller risk to the environment in terms of leaching.
Wesley Totten is a graduate research assistant and Bert McCarty, Ph.D., is professor of turfgrass science, both in the Department of Horticulture at Clemson University (Clemson, S.C.).
http://forums.gardenweb.com/forums/load/lab/msg041655342430.html
http://foliarfert.com/pages/introduction.htm
