By Sarah Robertson
Columnist | Posted: Sunday, June 1, 2008 12:00 am
It's amazing the things you discover when clearing out the garden shed.
Five opened containers of least-toxic fungicide, three cartons of Epsom salts; two unopened gallons of transparent deck stain, several tarps of varying size (still in their original packaging), a bounty of mismatched garden gloves and multiples of just about every fertilizer imaginable.
As I quietly pondered our plastic tarp collection, my spouse hefted a box of bat guano in one hand and several packets of almost-empty (but not quite!) snow pea seeds in the other.
"What's really scary is that I understand the bat guano," he said, shaking his head. "But please - can we ditch the seed packets and mate-less gloves?!"
I can't blame the poor guy. He built this space as a place for us both to share, but my gardening stuff tends to spill over into his tool/shop side on a regular basis.
This is especially true of fertilizers and related nutritional supplements. The products we use tend to be primarily organic in nature, and I'm always open to trying something that has worked successfully for someone else.
As a result, the shelves in our shed are often bulging with products designed to give the soil in our garden an added nutritional boost. I tend to use primarily organic fertilizers in our garden, and over the years have refined my favorites to reflect ease of use, effectiveness and cost.
Most of us tend to think about fertilizer in terms of nitrogen, phosphorus and potassium. All three are very important, to be sure, but there are a number of other ingredients - calcium, magnesium - and trace elements such zinc, iron and copper that can make a big difference in how well your garden soil supports healthy plants. What follows is a basic primer on some of these unsung soil-building heroes:
Calcium
Calcium is needed in greater quantities than perhaps any other nutrient. It's important for cell wall integrity, root development and leaf growth. Low levels of calcium in the soil cause a lack of vigor, which shows up as deformed new leaves and branches, weak stems and roots, and issues such as blossom end rot in tomatoes.
One good source of calcium is gypsum, which can also lower soil alkalinity. The most popular calcium source here in the Northwest is limestone, with dolomite limestone a good choice because it also contains a fair amount of magnesium.
Ground eggshells, buried directly into the soil of your garden or laid on top of the soil as a barrier against slugs and snail, are also high in calcium.
Magnesium
Although soils are seldom deficient in magnesium, the addition of this mineral can help in the production of healthy, long-lasting flowers - especially roses. Epsom salts, which contain about 10 percent magnesium, are an easy and inexpensive way to get this substance to your roses and other flowering shrubs.
Studies have shown that two half-cup applications of granular Epsom salts per season - the first in late winter, before rose buds break, and the second in autumn before leaves drop - results in thicker stalks, larger flowers and improved overall rose health.
Trace Elements
We all know that nitrogen, phosphorus and potassium are the three big essential ingredients for plant growth.
But if there were no trace elements in the soil, it would be impossible for plants to properly digest and absorb those ingredients. Trace elements such as sulfur, zinc, cobalt, iron, molybdenum, and boron help developing roots take advantage of all that the soil has to offer.
The difference between rich, fertile soil and poor, infertile soil is its mineral composition. The very flavor and nutrition in fruit, grains, and vegetables depends on available soil minerals - not the amount or type of organic matter. While compost is critical to soil health, promoting microbial activity and providing excellent organic matter, it's those minerals that create sweetness, flavor and nutrition in food.
A number of products contain trace elements in varying amounts, according to master gardener Paul James. Greensand, which is mined from old marine deposits in New Jersey, is ordinarily used to boost potassium levels. But it is also loaded with trace elements and it lasts in the soil for up to five years.
Alfalfa meal, a good source of nitrogen, also contains lots of trace elements, as do seaweed products such as kelp meal, and even animal wastes, including bat guano and worm castings.
Various rock dusts, such as granite dust and rock phosphate, supply good doses of trace elements and their benefits can last up to five years.