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The most common problem gardeners experience with fertilizers is a mis-communication or mis-understanding of the terms that describe them.

  • Fertilizer: A fertilizer is any substance applied to the plant or soil to increase productivity. In the U.S., any product sold as a fertilizer or plant food must include the percentages of N-P-K on the product label.
  • N-P-K: The percentages by weight of Nitrogen (N), Phosphate (P), and Potash (K) in a fertilizer. For example, a fertilizer labeled 4-1-1 has 4% N, 1% P, and 1% K by weight. This is true for both liquids and solids. A common beginner's error is attempting to make a custom fertilizer mix by volume instead of weight.
  • Minor and Micronutrients: Plant scientists have identified over 20 minerals required by plants for normal growth. The Primary nutrients are N, P, and K. For convience, manufacturers and retailers usually lump the others under the single name 'micronutrients' -- although a plant scientist would label Calcium, Magnesium, Sulfur, and sometimes Iron as 'minors'. It is important for gardeners to understand that there is a complex chemical relationship between all of the mineral nutrients. Too much or too little of one in the growing media can inhibit the plant from uptaking others. This condition can be avoided by choosing products and materials that contain a set of micronutrients that are balanced for plants.
  • pH: A numeric scale that indicates the acidity or alkalinity of a soil or liquid. The values range between 0 and 14. The value of 7 is neutral -- i.e., neither acidic or alkaline. A pH below 7 is termed acidic and a pH above 7 is termed alkaline. Most plants (including bananas) prefer a pH between 6.1 and 6.6 because it permits the maximum uptake of minerals. Naturally occurring substances that cause changes in pH are usually slow to act. In this case, you should make measurements over a period of months before adding any more. In contrast, liquid solutions manufactured for pH change in soils act very quickly. During the temperate times of the year, updates to the pH can be made in weekly intervals if necessary.
  • Salt: A dry form of a mineral compound, for example potassium nitrate. Although some salts (e.g., table salt) are alkaline, many salts are acidic. For example, water soluble fertilizers are typically salts and many of them form an acidic solution.
  • Urea form of Nitrogen: The urban myth is that it comes from urine, but in reality it is most often mined from dry lake beds in deserts. Note that if you are growing in a soil-less media, the proper microbes are missing to break down the urea for the plants.
  • Chemical Burn: This condition can be caused by (1) an over-abundance of a mineral nutrient -- the most common two are Sulfur and Chlorine, esp. from murate of potash, (2) the presence of a mineral form which the plant cannot process -- the most common being urea in soil-less media, (3) the soil being too acidic or alkaline -- i.e., the pH being too low or too high, (4) the presence of a chemical toxic to the plant such as an herbicide.
  • Plant Hormone: Plant hormones are not fertilizers. Instead, they are compounds (usually enzymes) which when applied to a plant will effectively 'signal' it to perform certain growth characteristics. Most commercially-produced plant hormones are substances which plants also produce during certain phases of the life cycle. Gibberellic acid is one of several common plant hormones available in various forms by manufacturers. Notice that the plant is likely to suffer if you signal the plant to grow but do not provide it with enough nutrition.
  • Soil Conditioner: Soil conditioners are designed to improve the physical and/or biological characteristics of a soil such as percolation, ionic exchange, and bio-symbiosis. Examples include perlite, pumice, humic acid, and mycchorizae. Soil conditioners are not plant food and not a fertilizer. Depending on the contents, U.S. labeling requirements might or might not require a listing of some or all of the ingredients.
  • Chelate: Some elements of fertilizers are highly reactive in raw form -- e.g., phosphorus. A chelate is a liquid or solid substance that keeps elements in an inert compound until the plant is ready to use it. Most commercial fertilizers use oils extracted from plants for this purpose because (1) they are the most effective way to deliver the nutrients to the plants, and (2) they are usually the least expensive substance available.
  • Composted: Biologically distilled minerals and/or soil ingredients from more or less raw plant and animal material. In the U.S., any product labeled and sold as compost must be cured for a lengthy period which depends on size of the heap, day- and night-time temperatures, materials in the heap, etc.
  • Mulch: any coarse-grained material applied to the surface of the soil which protects the soil in some fashion. In the U.S., mulch is not required to be composted. Notice that uncomposted mulch can contain unwanted diseases from some unknown location(s).
  • Natural: The substance(s) is/are from a naturally occuring source -- which might be biological or physical such as seeds from a tree, a rock quarry, or a dry lake bed. 'Natural' can also legally (U.S.) include materials that have undergone some processing such as mechanical sorting or the leaching out of wanted or unwanted materials in a tank or vat. This leaching process can involve ionic chemistry -- for example the addition of powdered calcium to a tank of dissolved minerals to cause wanted or unwanted minerals or metals to precipitate.
  • Synthetic: These can be substances which also occur naturally, or substances that have been invented by humans. All of them (U.S.) are substance(s) produced by covalent chemistry or a metal alloy process.
  • Organic: This can mean just about anything, since it is not a legally regulated term. Depending on who your audience is, the interpretation might be plant material, animal excrement, coal tar extract, or an organo-phosphate chemical synthesized from petroleum.
  • Government Certified Organic: In the U.S., this has little or no bearing on whether the substances are natural or synthetic. The legal definition for fertilizers is that they have negligible effect on the local environment. For foods sold as 'government certified organic' in the U.S., it does not mean they were produced without synthetic substances -- it means they were produced in a fashion that had little or no effect on the site where they were produced.
  • OMRI Certified Organic: Currently has the same meaning as Government Certified Organic, described elsewhere in this section.
  • CCOF Certified Organic: This is a very strict (and costly) certification. The CCOF will certify that no synthetic materials are present or have been used.

Specific Needs of Bananas

  • Fruiting Bananas: University studies from Yale, U of Florida, U of California, U of Hawaii, Tamil Nadu, etc. all conclude that fruiting banana plants can utilize up to 1 pound of Nitrogen per year and 1.5 pounds of Potash per year when planted in suitable growing media and space. Further, they uptake and interact with little Phosphate and in about the same proportions as Calcium and Magnesium. The proportions of micronutrients needed are the same as for most bulbs and tubors. Like most plants, the recommended pH is 6.2 to 6.3.
  • Ornamental Bananas: Far less Potash is needed, only 2/3 lb per year. Otherwise, the quantities are the same.
  • Plants Grown in Containers: A 'standard' size plant (8 to 15 foot pseudostem) in a 25 gallon pot will utilize up to 1/2 of the above amounts.
  • Small and Huge Plants: Small cultivars such as 'Truly Tiny' grown in a container can only utilize a 10th of the above quantities. The gargantuan 'Saba' can utilize twice those amounts in the subtropics and 3 times or more in the tropics.
  • Very Young Plants: 1/4 teaspoon (TC's) to 1 teaspoon (TC starts in 2" or 4" pot) of a water-soluble such as 20-10-20. More phosphate is needed during this stage to promote root development.
  • Plants Grown in the Tropics: In many parts of the central Americas, southern India, the Philippines, Hawaii, etc. the local environment will input about 1/4 lb of nitrogen per plant per year. Potash might also be present in the soils there, but after 7 years plants will typically have consumed most of it. The target nutrient proportions for these areas are 3/4 lb Nitrogen to 1.5 lb Potash. For example, Banana Fuel 15-5-30 is designed for the tropics.
  • How to Compute the Amount to Use: Suppose you have access to a fertilizer with N-P-K of 15-15-15 or 15-5-15 (better, because it is lower in Phosphate). To obtain 1 lb of Nitrogen per year, you will need to use 6 2/3 lbs of it because (1 lb N divided by 15%) = 6 2/3 lb. Notice that these formulas have the same percentages of Nitrogen and Potash. This means you are still short 1/2 lb of Potash because you wanted a total of 1.5 of Potash per year. This could be obtained from one of many Potassium supplements. For example, if you choose 0-0-22 as a supplement to 15-x-15, then you would need (1/2 lb divided by 22%) ~= 2.3 lbs per year. You could also save yourself the trouble of using two different fertilizers by obtaining one that has 1.5 times K as N. For example, 15-5-22 or 20-5-30.

Foliar Or Soil Drench?

It all comes down to total amount of nutrients delivered to the plant. You can choose to deliver them by foliar spray or soil drench. Since there is more capacity for storage and uptake in the soil, it takes many more foliar applications to deliver the same amount of nutrients as applied to the soil. If you use a water-soluble fertilizer, consider spraying some on the leaves when applying a soil drench.

The optimal time for foliar application is in the early morning when the plants pores are open to accept dew from condensation. Bananas are a monocot, so the side of the leaf you spray doesn't matter much. However, local humidity and temperature can favor the sun-ward side.

Nursery Fertilizers

  • Banana Fuel: 15-5-30. Great for the tropics but in the U.S. (esp. the midwest) you'll need Nitrogen supplement.
  • Going Bananas: 9-3-27. An excellent Potash supplement.
  • Grow More or Scotts (Fruiting Bananas): 20-5-30 natural water soluble with minors; maximum of 5 lbs (8.5 cups) per year per plant in the ground. For example, in a 10-month growing season apply 3/4 cups of 20-5-30 per month. Dissolve in water before applying.
  • Grow More or Scotts (Ornamental Bananas): 28-8-18 natural water soluble with minors; maximum of 3.6 lbs (6 cups) per year per plant in the ground.
  • Potassium Nitrate, also known as Saltpetre in Europe: 13-0-38 natural water soluble in pure form. Excellent potash supplement, also strong enough to be used on tree stumps for removal.
  • Seaweed Extract: typically 0.1-0.1-1.5 plus significant quantity of the plant hormone gibberellic acid.
  • Stokes Tropicals Banana Blend: 3 months controlled released fertilizer 6-2-12 w/minors.
  • Sul-Po-Mag, also called K-Mag: 0-0-22 plus 10.5% Magnesium, 22% Sulfur, and less than 2.5% Chlorine. Careful, in addition to Potash it contains large amounts of Magnesium, Sulfur, and a significant amount of Chlorine. It is an excellent potash supplement and soil acidifier but I do not recommend applying more than 1 lb per year to bananas.

N-P-K of Several Natural Materials

  • Banana Peel: 0-3-42. Has a high percentage of Potash and no Nitrogen. An average store bought banana has a dried peel weight of about 8 grams, so the net amount of potash per peel is about 3 1/3 grams. To acheive net 1.5 pounds of potash per year for a maturing banana plant, you will need about 510 of those peels. To be a meaningful supplement potted ornamental flowers, you'll need about 20 per month.
  • Composted Cow Manure: 0.2-0.1-0.2. Weak, relatively high in Phosphate.
  • Worm Castings (Vermicompost): 0.5-0.5-0.5. Worm castings are an excellent addition to any soil mix because they put low dosages of phosphate in the root zone. The worm flem present in the castings is also a food source for mycchorizae and other organisms beneficial to plants. However, agricultural studies (with control groups) in San Diego county have shown that worm castings applied to the soil surface are no better and far more expensive than composted mulch. Further, surface application of worm castings provides an environment for the growth of noxious weeds. Up to two hundred pounds of dried worm castings per year are needed to meet the full requirements of a single banana plant.
  • Composted Steer Manure: 0.7-0.3-0.4. A good soil amendment for herbs and veggies grown for leaf and/or stem; i.e., where flowering is not to be encouraged.
  • Composted Horse Manure: 0.7-0.3-0.6. Both sheep and horse manure are great soil amendments for fruiting veggies.
  • Composted Sheep Manure: 0.7-0.3-0.9. Not a bad ratio of N to K for fruiting bananas, but you'll need up to 143 lbs of it per plant per year.
  • Composted Chicken Manure: 1.1-0.8-0.5. Feed it to your lettuce and watch it bolt early.
  • Composted Sea-Bird Manure: 1-10-1. Great in tiny dosages if you are trying to stimulate root growth.
  • Alfalfa Meal: 2-0-3. An excellent ratio for most fruiting plants. An excellent addition to soil. As a sole-source, you would need up to 50 lbs per plant per year.
  • Composted Rabbit Manure: 2.4-1.4-0.6. A great addition to compost piles. Be sure to add more Nitrogen sources to counter-act the relatively high Phosphate content. Applied alone it will cause some leafy vegetables to bolt early, but herbs like oregano will be less affected.

How To Make A Custom Mix

Suppose you have two fertilizers, one to be used as a "nitrogen source" and another to be used as a "potash source". Obtain the N-P-K rating for each and denote them like this:

N-P-K of fertilizer #1 (nitrogen souce) = n1, p1, k1.

N-P-K of fertilizer #2 (potash souce) = n2, p2, k2.

Fertilizers #1 and #2 should met this criteria: D = (k2*n1 - k1*n2) > 0.

Pounds of fertilizer #1 to use per plant per year: A = (k2 - 1.5*n2) / D

Pounds of fertilizer #2 to use per plant per year: B = (1.5*n1 - k1) / D

First IMPORTANT note: measure by weight, not by volume.

Second IMPORTANT note: if these are liquids or water solubles, do not mix them or add them to your fertilizer tank at the same time unless the total Calcium percentage (add them) is less than 4%, and the total Magnesium percentage is less than 1%. If either of these are true, then you may add them one week apart to the plant or your fertilizer tank (in the case of the tank, assuming constant or weekly feeding).

  • Example -- supplementing Banana Fuel with a nitrogen source: Suppose you have Banana Fuel 15-5-30 and wish to increase the amount of nitrogen you are feed your plants with Fish Emulsion, 4-1-1. You would calculate D = (0.30*0.04 - 0.01*0.15) = 0.0105; A = (0.30 - (1.5*0.15)) / 0.0105 = 7.1 lbs per plant per year; B = ((1.5*0.04) - 0.01) / 0.0105 = 4.76 lbs per plant per year.
  • Example -- supplementing Triple 15 (15-15-15) with K-Mag (0-0-22): D = (0.22*0.15 - 0.15*0) = 0.033; A = (0.22 - (1.5*0)) / D = 6.67 lbs per plant per year; B = ((1.5*0.15) - 0.15) / D = 2.27 lbs per plant per year.

Members Methods

  • The Flying Dutchman: Dried Cow Manure and once in a week a liquid fertilizer(7+4+6)
  • MediaHound: I make a compost mixture with surplus material from the kitchen combined with most all organic waste from the yard. I'm now using use three UCT9.5 compost bins. I also use a variety of packaged commercial fertilizer and micronutrients. Seaweed, liquid fish, composted manure, etc. MediaHound 09:46, 24 April 2007 (EDT)
  • Patty in Wisc: Tomato food 18+18+21 because it has more K.
  • Pitangadiego: Triple 16 is cheap and effective
  • Chong: I find that since bananas are heavy Potassium feeders, any fertilizer that has the K component the highest, the N second, and P the least, would be advantageous since the majority of the banana make-up is Potassium. In any case, I don't think that the "P" component should ever exceed the "K". recommanded-15+10+30 or 15+8+27 E.g.
  • Joe Real: I use 6+27+27 XB with minors from BEST fertilizer brand. It achieves a nice balance of growth, pup and fruit production.
  • momoese: I use loads of steer and chicken manure as well as worm castings from my own red wigglers that have taken over the garden. I also use homemade compost and EB-Stone organic plant food 2-3 times a year.
  • Frankallan: I use aged rabbit manure
  • Rmplmnz: Compost tea wich is more or less a liquid version of compost. You take your solid compost, and soak it in water and let the mixture sit around for a few hours or a few days. Then you pour the liquid through a screen, or through cheesecloth or something similar to strain out the solid material into a bucket. What you have then is compost tea. Compost tea is great, because it is a very mild, organic liquid fertilizer that provides beneficial live organisms that improve the soil where you use it. It doesn't burn plants like store bought fertilizers can.If you can not find any of the above dump a bag of cow manure in the trash can and fill with water..
  • Bananimal: I use a custom fertilizer blend of 6-2-12 with minors. And especially important - I apply fert monthly. Up to 3 pounds when the plants are bigger and show real vigor.
  • FunSoCalTiger: I use a balanced granular slow-release such as Dynamite 13-13-13, Osmocote 14-14-14, Vigoro 17-17-17 or MiracleGro 10-10-10 every couple months or so and at planting. I also use any of several water soluable mixtures at 1-2 times the recommended doseage/frequency such as the balanced Peters Professional or MiracleGro Select 20-20-20 or the MiracleGro Tomato Food 18-18-21 (has slightly more K and also has some Magnesium). I also supplement with Epsom Salt each week to boost the Magnesium content at the rate of 1-2 teaspoon per gallon.
  • Nanaman: I use about 50% Jungle Growth potting mix, 40% composted cow manure, and about 10% added vermiculite, plus a few handfuls of Pre Plant Plus 7-5-7 organic fert. I fertilize about once a month with whatever I have on hand at the time, some times palm fert., some times 10-10-10, miracle grow, etc... I water them every day, sometimes twice a day if its really hot, which it usually is. In colder climates this mix may hold too.
  • Richard: 5 lbs of water-soluble 20-5-30 with micronutrients per maturing plant in the ground per year, applied monthly during the growing season.



(credit the flying dutchman)