Measuring up soil tests

Being curious as to how soil tests might compare, I did a home soil test on the same sample of vegetable garden soil I sent off to the Soil Nutrient Analysis Laboratory at UConn.

home test vs soil lab test

home test vs soil lab test

 

The results reveal some interesting differences.

It is no surprise to have both tests note low nitrogen – vegetables use up nitrogen quickly each growing season.  Both tests also note high phosphorus.  One difference, however, is in the respective potassium ratings – the home test listed low while the soil lab came back “optimal.”  This variation in test results will likely not make a difference, as I only plan to add composted manure to increase nitrogen levels.

Another difference is in the tests’ pH results.  The home test shows borderline high pH of 7.5, while the soil lab test shows a neutral pH of 6.9 (7 is dead neutral) … much closer to vegetables’ general pH preference range from 6.0 to 6.8.

The test comparison tells me the home kit should be good for basic N (nitrogen), P (phosphorus), and K (potassium) spot checks, but to question the accuracy of its pH results.

The soil lab test offers other advantages over a home test that are particularly important to would be green-thumbers.  Soil lab results come with information on how to interpret results, recommendations on how to address imbalances, and information on soil structure and organic content – both important moisture and nutrient retaining factors – and how to improve both.  Since the soil lab confirms my soil as sandy loam with high organic content, I know my use of home-made compost has remedied a prior low organic content test result from the soil lab (I also know I’ve improved a previously too high 7.6 pH as described in an earlier Soil Test post).

The soil lab additionally tests for calcium – insufficient levels contribute to the black sunken spots known as blossom end rot in tomatoes and summer squash – and magnesium which helps seeds form, as well as trace elements (boron, copper, iron, manganese, zinc, and aluminum).  To keep your head from spinning, the soil lab explains why each nutrient is important and how to fix imbalances … and the website links to all kinds of other fact sheets (preparing a new garden bed; purchasing top soil or potting media; fertilization to name a few).

Granted, I tested just one home soil test kit.  There may be others that give more in depth information, but when all’s said and done, the $8 (plus less than $2 for mailing) soil analysis from UConn is a valuable investment that permits gardeners to direct sometimes pricey soil amendments to the greatest advantage – both for the soil and the budget.

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Filed under Edibles, Gardening, General, Soil

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