Now that we've got many of our seeds started it's time to start thinking ahead to transplant time. Adios, down jacket! Hello fingernail dirt!
Before you consider the wholesomeness of your soil for your plants, get a heavy metal test to make sure that you don't have lead, mercury or the like in your yard. Heavy metals are neuro toxins, i.e. they poison your BRAIN! So if you are fastidious about nothing else, be fastidious about this. I got mine through UMASS. Get info at
http://www.umass.edu/plsoils/soiltest/
Here in Somerville we have many houses with lead paint and many residential lots that were industrial sites in the past so heavy metal contamination is prevalent.
Once you have made certain that your site is free of heavy metals it's time to check your pH and macro-nutrients. If you remember anything from high school chemistry... or in case you don't remember a thing, pH is the scale by which acidity and alkalinity are measured and for most plants, you want a pH in the neighborhood of 7 (1 is most acidic, 14 is most alkaline). Slightly below 7 will keep most vegetables happy. The macro-nutrients are nitrogen, phosphorus and potassium.
Some testers are meters with metal prongs and others are tubes in which you place about 1/2 teaspoon of soil with the contents of a capsule and distilled water. I chose the tube variety because the kit included tests for pH and all of the macro-nutrients. They cost about $4. I picked up four so I could test before planting anything then make changes and test again, then test once more in the middle of the season.
Nitrogen is the most important early in the season because it contributes to leaf growth and general hardiness but later in the season, too much nitrogen can lead to very leafy plants with few flowers and thus few fruits. Potassium promotes root growth so if your target product is a root (eg. carrots), favor potassium over nitrogen. Potassium also works in tandem with phosphorus to help reproductive organs like flowers and fruits grow. I'm not a chemist or a botanist, but from what reading I've done, I've gathered that ample nitrogen is very important when you first plant and potassium and phosphorus gain import as the season progresses and harvest time draws nearer. If you've got several soil tests on hand you can make sure you have proper levels of each element throughout the season. To make it more complex, if the soil pH is not correct, some minerals will not be accessible to the roots even if they are present at appropriate levels.
If your soil is anything like mine, it's been neglected for years and isn't exactly prepared to nurture your delicate little seedlings but don't fret, it's not time to transplant yet and you have some time to make corrections- and if you've tested, you can make targeted corrections.
Here's a quick guide I've compiled using two books (Botany for Gardeners, and The Gardener's A-Z guide to Growing Organic Food)
Problem Solutions
Too acidic Add limestone
Too alkaline Add sawdust or sulphur
Not enough nitrogen Add compost, manure, or fish emulsion
Not enough phosphorus Add compost, bone meal or introduce worms
Not enough potassium Add compost, kelp, worms, rock potash,
or crushed granite
