Simple Tips for Better Garden Soil
(Page 3 of 4)
April/May 2009
By Barbara Pleasant
Should You Test Your Soil?
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Mulching with grass, leaves, hay or other organic materials is always a good idea for all types of soil, but what other soil amendments might you need? Soils that tend to be too acidic or alkaline make it difficult for many plants to take up nutrients, so pH is one soil characteristic that calls for a fact-finding approach. An acidic pH below 6.0 can be nudged upward with lime, and an alkaline pH above 7.5 can be lowered with sulfur, but neither should be used unless you know your pH is way off.
The $15 or so invested in a laboratory soil test arranged through your extension service, or a do-it-yourself soil-test kit, will be money well spent, because it will tell you what you have to work with. I like home soil-test kits because I can quickly check the pH in different parts of my garden and get a general idea of major nutrients present, too. These kits are sometimes dismissed as unreliable, but a recent study conducted by University of California soil scientists revealed that two brands — Rapitest and LaMotte — give accurate pH readings more than 90 percent of the time.
Getting Nitrogen Right
Unfortunately, no soil test can answer your most pressing question: Is there enough nitrogen present to meet the needs of the plants you want to grow? A soluble, slippery nutrient, nitrogen is hard to measure because temperature, pH, cultivation and many other factors affect its availability. Even if you know the history of the soil in a certain bed — including the amendments added and the crops grown — guesstimating nitrogen is a sticky business.
Ideally, you want to make sure that crop plants have just enough — but not too much — of this essential plant nutrient customarily found in manures, seed meals and dead plant and animal matter.
Nitrogen is probably already in good supply if you have been increasing the organic-matter content of your soil by digging in compost and using biodegradable mulches for several years, because organic matter stores nitrogen. Cool temperatures keep much of it locked away, but as temperatures increase, more nitrogen becomes available to plants. If you over-fertilize in spring (as many folks do in an attempt to speed up growth that is being held back by cool soil temperatures), it can backfire in a big way. Plants may grow to monstrous size, but they won’t start flowering until they have used up all that luscious nitrogen. You would have had a better crop with no fertilizer at all!
