Tuesday, March 16, 2010

Soils and Plant Nutrition

Plant Nutrition goes hand in hand with Soils. After all, with the exception of oxygen, hydrogen, and carbon, all the other plant nutrients come from the soil.

Plant nutrients are classified by how much a plant needs to grow. The macro-nutrients, needed in large amounts, are carbon, oxygen, hydrogen, nitrogen, phosphorus, potassium, sulfur, calcium, magnesium, and silicon. Micro-nutrients, needed in very small amounts, are: iron, molybdenum (molly be damned, if you are a James Garner fan), boron, copper, chlorine, nickel, zinc, sodium and manganese.

In areas where the plants are undisturbed, like a forest or prairie, the nutrients cycle from the dead plant materials left to decompose on the soil. The nutrients are then taken up by the growing plants; dead plant material falls to the soil to decompose, etc.

In our gardens, we remove the dead plant material because it is unsightly (in our eyes) and it can lead to fungal diseases and insect infestations in our growing plants. Because we remove the dead plant material we need to add fertilizer to ‘feed’ our plants.

Plants are not able to discriminate synthetically produced nutrients from organically produced nutrients. Nitrogen is nitrogen to a plant. It is the soil that is damaged from the use of synthetic or even condensed organic fertilizers because there is nothing for the biota to feed on. We need the animals, whether large or microscopic, to burrow through the soil making pores for air and water and roots.

Like I said in Part 1, soil is a dynamic system, ever changing.

About 20 years ago, an older gentleman of my acquaintance, had an infestation of European Crane Fly, Tipula paludosa, larvae. The local farmers coop recommended a synthetic insecticide. The gentleman was so concerned about the patches of bare lawn, he doubled the dose.

The next morning he was astonished to see the lawn covered by dead worms and insects. Oh wow, what had he done?

I suggested he get a load of compost and spread it over the entire lawn, raking it down to the soil. Then, buy a couple of pounds of worms and scatter them about. Water about one inch a week and let nature take its course. I also advocated the use of coffee grounds sprinkled about for worm feed. He ignored me, choosing instead to over fertilize and over water. I got to see first-hand what dead soil looked like, it wasn’t pretty!

It took years for the soil to rebound. It compacted due to no animals living in it. The gentleman tilled and replanted the lawn at least twice in five years. The grass did not grow well at all, even with over fertilizing with synthetic fertilizers. Thanks, in part, to the gentleman learning about composting and his applications of compost to the flower beds running around and through his acre of landscape.

The moral of the story, soil needs the biota (living and dead plants and animals) to support its health. And to that end, I suggest using compost to feed your soils.

I covered how to make compost before. You can also buy compost from nurseries, farmers coops, or businesses that specifically deal in soil amendments.

Spreading three to four inches and tilling it into your veg garden every year, will feed your soil and your plants. I add compost to my landscape beds about every three years. I use hemlock bark to ‘finish’ my beds and it will last about three years before I need to add more. I spread the compost, dig it and the remaining bark into the soil, and finish with the hemlock (a dark brown color and it doesn’t have the splinters doug fir has.)

I use a slow release fertilizer every spring. Yes it is synthetic. I don’t apologize for that. The plants need a little extra nitrogen because of the hemlock using nitrogen to break down

Adding compost to the lawn is so simple. Just toss it about with a shovel, best not done on a windy day. You are only going to put down about an inch or less. Rake the compost into the grass and water one inch per week for the growing season. I do this every year along with using a mulch mower. I have one of the greenest lawns on the block.

I also spread one pound of Epsom salts per 1000 sq ft, over my entire property. The Epsom salts are magnesium sulfate. Plants use magnesium the same way we use iron. Iron is the center of our red blood cells. Magnesium is the center of the chlorophyll cell.

We have slugs. Everywhere. When we bought this house, the slugs were so large they looked like dog poop! And they climbed the trees! I have tried wood ash in small amounts, copper strips, and deadly poisons to no avail. Upon reading about iron phosphate, I stocked up and use it. It’s safe for kids and pets, kills the slugs, and fertilizes the plants.

The past ten years I have been dusting the entire property with lime, calcium carbonate. I put down less than ¼ inch to help raise the pH of the soil. I don’t test the soil; I do know from my studies that using nitrogen fertilizer increases the pH of the soil. By adding either lime or dolomite (calcium, carbonate, magnesium) you will raise the pH. If you want to use dolomite, I strongly urge that you do not use Epsom salts as the dolomite already has magnesium.

Feeding the soil feeds you plants by feeding the living critters that live in it. Compost helps to loosen clay and to increase water retention in sand.

Just a reminder, over fertilizing leads to run-off into our lakes and streams. That run-off causes algae blooms which lower the oxygen levels in the water. Lower oxygen levels kill off the fish and other aquatic animals. Please be a concerned gardener and remember, ‘Moderation in all things.’

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