WTF! What the Fertilizer! Anyone else suffering from Fertilizer Frustration? It boggles the mind with how many options there are in fertilization! There are so many options and recommendations for vegetable garden fertilization. There are so many myths and home remedies and “my grandpa did it this way” stories. With that being said, there is no one size fits all for every garden but it does help to have a good working knowledge of the  nutrients in fertilizers and what their purpose is in relation to plant growth and production.

If you have even just started to scratch the surface dirt of fertilizer research, you probably already know what those three little numbers on the bag or bottle represent. Respectively, they represent Nitrogen, Phosphorus and Potassium (sometimes called Potash). Theybare always listed in the same order. Hence, 10-10-10 would be equal parts of each and 10-20-10 would be double the phosphorus as nitrogen and potash.  Ok? Now what? If you were like me you have many questions regarding this: how much do vegetables need of each nutrient,  what does each of those nutrients do for the plant, how often do I use each type, when do I start fertilizing, and do I really need to fertilize? I don’t remember the “old timers” out there with their miracle grow specifically designed for tomatoes, peppers, roses, etc. After a little research I have some answers for these questions (ok! a lot of research)!

First remember, gardening mastery does not occur in one season. It is often trial and error. I’ve had many garden failures. Success depends on many factors some you can control and some you cannot. Factors include your soil type, weather trends, seed germination rates, animal and insect control, weed control, soil care or amendments, etc. . Soil testing is the most definitive way to amend soil for optimal soil health for the best plant growth. GET YOUR SOIL TESTED! Initially, it is probably best to have your soil tested every year until optimal health is reach consistently for two consecutive years and then  you could probably switch to every other year.

If you are like me, you keep putting off getting your soil test but need some guidance on how to feed your plants. Before we talk about when, where, and how much fertilizer , lets discuss the why! Why? because we want strong healthy and productive plants.  We all have to eat including the plants. Knowing what each nutrient does for the plant helps us determine what concentration/ratios that we want to use.  For the purpose of this post we will discuss the functions of nitrogen, phosphorus and potassium; however, there are many other important trace minerals and elements such as iron, zinc, sulfur (sometimes the 4th number on they bag or bottle) magnesium, etc. that plants use.

Now let’s get the down and dirty on these three key nutrients. Nitrogen is truly needed in some degree for ALL parts of the plant — the roots, leaves, stems, flowers and fruits. However, it is primarily responsible for the green part of the plant and is needed to form protein. It does this by enabling the plant to make chlorophyll. Nitrogen deficiency usually shows up as stunted growth or pale greenish yellowing leaves. Fertilizers with too much nitrogen combined with soils deficient in the other two main nutrients (phosphorus and potash) result in big green plants without flowers hence decreasing fruit production. Fertilizers with exact amounts of nitrogen, phosphorus and potassium such as 10-10-10 or 13-13-13 should be used on plants that are all green such as grass and corn but not on flowering plants such as tomatoes and squash. Ideal ratios for flowering plants should be 3-1-2 which include 6-2-4 and 9-3-6. Be cautious, way too much nitrogen can also kill your plants. You can always add more but you can’t take it away after you add too much. Fish emulsion and blood meal are good sources or organic nitrogen, 5-1-1 and 12-0-0, respectively.

Now you ask: well how do I get good flowering and fruit production? Its the phosphorus! Phosphorus is responsible for cell division to help root formation, flowering and produce fruit. Good sources of organic phosphorus are bone meal 1-11-0 and the very slow acting rock phosphate or colloidal rock phosphate. I really like Jobe’s organics for good flowering with a concentration of 2-7-4 which is not the recommended 3-1-2 ratio but I fertilize with higher nitrogen concentration initially for increased green growth and increased nitrogen needs during periods of rapid growth.

In my area (rocky Central Texas) I do not use bone meal because I suspect I already have high phosphorus because of the high prevalence of limestone in the soil. Moreover, I do not want to make my soil any more alkaloid than it is already. Bone meal will make your soil alkaline and blood meal makes it more acid. I need the acid.

If I still lived in East Texas I would use more bone meal since there is more pine and acid in the soil. Please check out my previous post titled “Love the Soil You Are In” for further information on soil types.

Finally, Potassium (Potash) keeps your plant healthy by protecting from disease and facilitating micro-nutrient absorption. Potassium is also important in root development and helps with photosynthesis. Luckily, potassium and other micro-nutrients are likely already present in your soil. So it doesn’t need to be replenish at the same rate as nitrogen and phosphorus per se. A slight excess in potassium is not harmful to your plants. So, if you are concerned you may have low potassium (really you shouldn’t be if you haven’t had your soil tested [stating that] —it is unlikely), wood ash and glauconite rock are good organic sources of potassium if needed. Again, soil testing is the best way to know exactly what your soil needs and eliminates the need for speculation.

First question, when do I start fertilizing my soil? Ideally, you should be putting out organic matter in late winter given its slow release into the soil. Examples or organic matter for your garden should include things like manure or compost. This is especially important for areas where you will be putting your heavy feeders such as tomatoes, broccoli, brussel sprouts, cabbage, cantalope, etc. Remember, the heavier the harvest should equal the heavier the feeding the following year or growing cycle. If you are starting seeds indoors, you will need to start with a mild fertilizer once you have true leaves. The cotyledons (first leaves) have enough nutrients to support them until true leaves develop.

I like to try and stick with organic fertilizers (disclaimer I am not afraid to throw a chemical fertilizer on my plants {not seedlings} if they need a quick boost because they are looking tired and hungry).  Initially, I like to start my seedlings with fish emulsions diluted to half strength. I like this because it is mild, organic and I can dilute down easily. It is 5 times higher in nitrogen than phosphorus or potassium. I am trying to encourage green growth initially not necessarily flowering and disease resistance because they are young and protected in a nutrient rich potting soil at this time. I want them to be green and strong.

Then before I transplant or start seedlings in ground I pre-treat my my soil with blood meal to add nitrogen again until my plants are bigger and ready to start flowering. In the off season we also dump our horse manure in the garden. This year we also added some turkey manure and mushroom compost we bought. In addition to a small composting corner we use for kitchen scraps. This is a little tomato seedling that came up after we spread the compost!

Once they get bigger and more green, (approximately 4 weeks later) I use Jobe’s organics for things that will be flowering such as tomatoes, peppers, eggplants and squash. This is because it has a higher concentration of phosphorus. Things like corn, cabbage, and asparagus I would use equal parts of NPK+ to promote green growth. If the plant has really been struggling with growth I will also use my trusty old miracle grow I mix up in my watering can. I do this because it is quickly used by the plant. The new asparagus loved it!

For me it is easier to think about what the plant needs during its life cycle and what my goals are (green growth, flowering, disease resistance, nutrient absorption) in relationship to fertilizers versus memorizing multiple different numbers and concentrations. If I want green growth I need nitrogen, if I want flowers, I need phosphorus, and if I am worried about my plant absorbing nutrients and disease fighting ability I will throw a little potassium at it. Remember to read labels and follow recommendations for application procedures and types i.e. side dress, band/row application, broadcast, starter solution, etc. and most importantly the recommended about. You don’t want to over do fertilizer!

If this year’s soil doesn’t agree with your plants make the changes you need and look forward to the next season.

~Chas