A Load of Manure — Your Guide to Fertilizers

"I hate manure." --- Biff Tannen

In gardening, you have to work with the land you've got. This might mean tilling up a vacant lot. It might mean making a bed in a suburban yard where you're not sure what the soil conditions are. It might mean gardening in miniature if you're working with containers.

Even if you're lucky and the soil you're using is absolutely perfect, over time the plants will consume nutrients and drain the ground for everything it's worth — changing the look and feel of the soil.

So, growing plants means occasionally giving plants what they need to grow. Your goal is to have a rich, light, dark, loamy soil that is full of organic material. To check on your soil, you could do all sorts of things. They sell home testing equipment, and you could even take a jar of it to your local university extension and pay a few bucks for an official soil test. I use a different method altogether.

Turn up a shovelful of soil and count the worms. The lowly earthworm is maybe the best single indicator of how healthy your dirt is. If, in that shovelful, you can spot 5-10 earthworms, then your soil is the place to be for living things. That's good. If worms like your soil, then plants will too. If you can't find that many worms, then you know you have some work to do.

First, let's have a word on organic nutrients vs. chemical nutrients.

Why should compost be better for a garden than a bag of Miracle Gro? After all, if you look at the chemical content of the ammonium nitrate whatever, you can see that the chemical fertilizer contains two or three times more of the stuff plants need than an equal amount of organic fertilizer like compost or manure. But how much of it can a plant use? And what good do these chemicals do for your soil?

The difference between chemical fertilizer and organic fertilizer is like the difference between taking a multivitamin every day and eating junk food vs. eating a well-balanced diet that contains all the nutrients you need. That artificial stuff poured on top of a poorly maintained diet might do your plants some temporary good, but it can also easily wash out of it. Since the nutrients are so concentrated, it's easy to over-apply and shock the plants' systems.

Basically, the artificial stuff is not going to address many of the problems that you might have with gardening. Miracle Gro doesn't add organic materials to your soil, and once it washes away, it's gone. At that point you either have to add more, or start building a garden right. Many of your organic soil amendments are made from plant-based materials, minerals that occur in nature or animal-derived products that add nutrients to the garden slowly, and are absorbed over time — promoting long-term health for everything that lives in your garden.

Don't get me wrong. Chemical fertilizers have their advantages. Mainly, they work really fast and are easy to apply. If you time the application right and use the right amount, they can have some amazing results. But nothing does more good for your garden than ensuring good soil and plant health with organic materials that give your plants everything they need from root-hairs to leaf-tips. Storebought bags of chemicals do absolutely nothing for soil health and structure. In fact, the harsh chemicals sometimes used in these mixes can kill, hurt or drive away beneficial micro- and macro-organisms that create the best environment for your plants to grow in.

Without beneficial natural organisms and adequate organic materials in your soil, the ground will become sterile and lifeless. It will dry out and become compacted, strangling roots and holding water inefficiently. At this point you could spray on some more chemicals, but you'd only be making a crappy garden look less so. You wouldn't be giving the plants what they really need. This isn't hippie propaganda, either. It's science. And you can see it work too if you have the patience for it.

In the end, the choice is up to you. You can use lab-created chemicals and artificial fertilizers, you can use the stuff that's closer to what would help plants grow in the absence of people, or you could use a combination of the two.

As for me, I have no interest in giving nature a kick in the pants. Gardening is something that has taught me patience. You have to approach plant life on its own terms and understand what they need to grow. There are no short-cuts in gardening. Plants take their time, and so should we when we're looking after them.

Now that I'm off my soap box, let's talk a little about SCIENCE! There's a bit of chemistry involved in gardening, and the lives of plants hinge on three little elements: N, P and K.

Human beings have to go out and get our foods like suckers. Plants, on the other hand, have it figured out. They just sit there, and they make their food from the sun's rays, like we all learned in grade school. But to photosynthesize properly, they need three key nutrients: Nitrogen, phosphorus and potassium.

Have you ever noticed the set of three numbers on a bag of storebought fertilizer? It might say 25-30-10, for example. This means the fertilizer contains 25 percent nitrogen, 30 percent phosphorus and 10 percent potassium. Plants need these three nutrients like we need carbohydrates, fats and proteins. And just like us, they need to be in the right balances. Too much of a good thing can do just as much harm as too little. So now let's go over what these nutrients do, and talk about some ways to introduce more of them into your garden when they're needed.

In short, nitrogen is what makes plants green. They can't produce chlorophyll without it. So it shouldn't be too surprising that nitrogen-starved plants can look yellow and wilted. A plant can die of lack of energy without enough nitrogen. On the other hand, too much nitrogen can cause plants to focus too much on vegetative growth and they'll neglect their other important functions, such as putting on flowers and fruit. In extreme cases, excessive nitrogen can "burn" plants, turning them brownish yellow and wilted. You can flush away an excess of nitrogen with more water.

Good sources of nitrogen for plants are: Blood meal, compost, poultry manure, steer manure, swine manure, coffee grounds, feather meal, litter from livestock pens, alfalfa meal, rabbit manure, urea, fish emulsions, compost "tea," wastewater sludge, and water from a tropical fish tank (provided it's not salty). Growing nitrogen-fixing plants (clover, alfalfa, rye, oats, etc.) will boost nitrogen in the soil, and at the end of their growing season you can till them under your bed. Horticultural-grade charcoal will actually trap nitrogen for your plants to use, although the charcoal doesn't add any nutrients itself.

The second macronutrient, phosophorus, is needed in large amounts by plants. Plants with enough phosphorus will grow right on schedule and start giving you flowers, fruits and veggies exactly when they should. It's particularly important for plants to have adequate phosphorus when they are young or have been freshly transplanted into your garden because phosphorus encourages root growth. A plant with not enough phosphorous can look spindly and have darkened leaves with telltale purple margins or streaks. They will mature slowly, fruit poorly and sometimes produce no flowers or seeds.

It is hard for a plant to get too much phosphorus because they need so much of it and it's difficult for them to absorb in the first place. However, too much phosphorus in the soil can cause toxic chemical runoffs, which are harmful to the environment.

Good sources of phosphorus for plants are: Bone meal, rock phosphate, bat guano, fishbone meal, worm castings.

Potassium, also known as potash, helps plants build healthy cells that hold water well and perform all their metabolic functions properly. Signs of low potassium in plants include blotchy purple or spotted foliage, curled-up leaf tips, low crop yield, poor flower production and inferior crops. Plants without enough potassium are weak and more vulnerable to diseases and insects. They will also drink up more water than they should. Plants with a good amount of potassium, conversely, are tough and can resist droughts, bugs, diseases, and anything else the season can throw at them.

Good sources of potassium for plants are: Composted wood ash, composted banana peels, composted bracken ferns, seaweed meal, kelp meal, greensand (ground-up corals), muriate of potash, sulfate of potash, granite dust, cow and horse manure.

There are also any number of micronutrients in soil that are important for plant growth. To name a few, there's cobalt, zinc, copper, molybdenum, manganese, sulfur, iron and calcium. These are important not just for the plant's nutrition, but for your own (provided you're eating the plants). There are too many of these nutrients for me to go into here in this post, but look for them as the listed ingredients on any soil remediation products you might buy.


If you're still not sure what to do now that you've read all this...
I'll just tell you what I do. I get by most years with lots and lots of compost to boost soil condition, some steer manure and/or peat moss to loosen up the soil, and some blood meal and bone meal to add nitrogen and phosphorus to the soil. It works pretty well most years, and is totally organic.