Homegrown Column May 30, 2009
What is best fertilizer numbers for a garden in Rangely. We have very poor soil with zero in it.
The place I usually tell people to start in cases like yours is with a soil test. This will tell you exactly what your soil is like nutrient-wise as well as give you valuable information on pH, organic matter and soluble salts. This information will enable you to provide the right nutrients for your plants. Having said that, here’s a primer on fertilizer for this area:
We apply fertilizers to plants to provide the nutrients they need for proper growth and development. There are 16 essential plant nutrients. Three of them are gasses (oxygen, carbon and hydrogen) which are taken primarily from the air. The other 13 are minerals that the plant absorbs from the soil. These minerals are divided up into three groups: primary nutrients, secondary nutrients and micronutrients.
When you look at a bag of fertilizer there are three numbers printed on it. This is called the analysis and tells you how much of the three primary nutrients are in the fertilizer. The first number is the percentage of nitrogen, the second is the percentage of phosphorus and the third is the percentage of potassium. There are other major nutrients (the secondary nutrients) plants need like calcium, magnesium and sulfur but they’re either already present in our soils in adequate amounts or they’re also in the fertilizer. The last is a whole group of what are called micronutrients which are necessary for plant growth but in smaller amounts. These are things like copper, zinc, iron, boron, manganese and others.
The primary nutrient plants need in our soils is nitrogen. Be aware that not all nitrogen is the same. Some are quick release like nitrate and ammonium forms, some a bit slower, like urea, and others quite slow. I like using fertilizers with slow release forms of nitrogen.
They give plants a slower, more even fertilizing and you don’t have to apply them as often as faster release products. If you look at the fine print below the analysis numbers it will tell you the breakdown of what forms of nitrogen make up that fertilizer. Slower release forms of nitrogen cost more but I think they’re well worth it. I like fertilizers with 20 to 30 percent total nitrogen.
Phosphorus and potassium are generally available naturally in our soils in adequate amounts so we don’t have to be looking at adding a lot. I like adding a bit (usually less than 10 percent) since they will deplete slowly over time.
The main micronutrient we’re lacking is iron but I have seen deficiencies of zinc and copper as well. You want to use a fertilizer that contains iron. I like to see 3 to 4 percent in a bag. Many granular fertilizers don’t have much in the way of most micronutrients; you may have to use a product like Fertilome Liquid Iron (in spite of the name, it contains several other micronutrients besides iron). It’s also important when you’re fertilizing with iron that you also apply nitrogen with it. The two work together and you’ll see much better results if you do that.
One last word of caution: fertilizers aren’t a magic pill you can give to your plants to make them grow and thrive in our challenging soils. There is no substitute for good soil preparation before planting by mixing in good amounts of well decomposed organic matter. This provides at least a start on creating a soil environment where plant roots can grow and thrive.
I have flowering inside hibiscus that hasn’t bloomed since early winter with lots of new growth getting real leggy. What can I do to make it bloom?
Tropical hibiscus usually don’t bloom well inside the house because of a lack of light. It’s surprising how much darker even a bright room indoors is than outside. What I would do is to move the plant outdoors to a spot where it will get some shade in the afternoon. Cut it back a bit to reduce the legginess which will also stimulate lots of new growth. Since they bloom on new growth, you’ll have more flowers on the plant this summer.