Go get your soil tested

It’s almost spring and now is a good time to get your soil tested if you didn’t do it last fall. This gives you just enough time to interpret the results and make some changes before you fill your beds with plants. Otherwise you will have to wait for late summer or fall.

I bet you didn’t know that soil science is also a study in philosophy and culture. Different groups have conflicting viewpoints of how soils work like the organic community, biodynamic farming and even hired professional farm consultants. The most influential group is the agricultural colleges and land grant universities.

soiltestUniversity teaching is geared towards chemical agriculture and their experts do not necessarily subscribe to some of the competing ideas from the other groups. Unfortunately the typical University material downplays the differences in food quality despite abundant evidence to the contrary. The belief that an apple is an apple is an apple works well for industry, but not for the consumer. I’ve found the most useful information actually comes from a handful of agricultural consultants and black sheep professors. The ag-consultants jobs are dependent upon results, and not upon published papers, and results are what we care most about. My article on pH was a small example of this conflict in ideas.

Because of this, not all soil testing labs are equal. Understandably, most labs are oriented towards chemical agriculture and work well for that particular use. I hold the belief that our results can far exceed that and picking the right soil test is part of the puzzle. I’m over simplifying here but there are basically two groups of soil test labs out there. The first are those that attempt to identify total nutrients using strong acids to extract the minerals from the sample, this is the type normally used by universities and chemical-ag. The second group are those that try to identify what they call available nutrients by using weak acids, under the belief that this more closely represents what plant roots have access to. Both types have value for different reasons, but I put a lot more emphasis behind available nutrients.

The other thing to consider is what nutrients are tested for, and not just how they are tested. My local soil test lab only covers various forms of Nitrogen, Phosphorous and Potassium. These are the big three nutrients from chemical-ag philosopy, also knows as NPK. Unfortunately you can not get a best of class product using the NPK method. Great produce is only possible in well balanced soil, which means testing for a whole lot more. At a minimum the test should cover at least 10 nutrients if not 20 or more, 3 is just grossly insufficient.

Soil balancing is a very big topic, but I don’t want you to wait for me to write 20 more articles when you can make the necessary improvements to your own gardens now. Go get a soil test and pay the extra cost for the recommendations. Please remember that soil testing is just one of many tools we will be using. It is not the final and only thing you can do to improve your food quality.

Soil Test Labs  I recommend:

  1. Logan Labs – this is the lab that I use
  2. International Ag Labs
  3. Midwest Laboratories
  4. Kinsey Ag

For more information in book form on the topic that are well suited for gardeners:

  • The Intelligent Gardener by Steve Solomon
  • The Art of Balancing Soil Nutrients by William McKibben
  • The Ideal Soil by Michael Astera

~Sean

pH part II

In the first part of this article, I presented what the conventional approach to pH is, what it’s accused of doing, some ideas on how pH actually works in the soil and should have impressed upon you the notion that pH is hardly what it’s made out to be. There’s a claim that “good plant growth” can’t be assured unless you fix your pH, but I counter that notion and state that this assurance can only come from appropriate soil mineral nutrition.

pH is not a cause… it is an effect.

It is the reflection of the the soil makeup. In our case we want nutrient rich crops growing in fertile soil with the most happy pH of 6.4. This would afford maximum nutrient availability to the plants. If however your pH is too high or too low, the pH is not the cause of poor plant health rather it is sign, a message to you about the state of your soil mineral balance and biological activity. It’s also not the end of your gardening career if you can’t achieve the perfect reading, many native soils can be difficult to impossible to move very far. If you can’t get your pH into the ideal range experiments have shown that if a plant’s roots have access to adequate nutrients and there is no toxicity then pH makes little difference. Therein lies the crux of the problem, availability of nutrients is the limiting factor, not pH. A strongly acid or alkaline soil may be a sign that soil nutrition is in bad shape, but that can be mitigated by excellent biology.

vinesCalcium lime is not the only material that can raise the pH either, so can magnesium, sodium, carbon and potassium. Likewise sulfur is not the only mineral that will lower the pH, so will phosphorous and chlorine. On your typical farm, the heavy use of salt fertilizers creates a situation of rising pH levels, where calcium is not then being applied, resulting in a calcium deficient soil, followed by cascading nutrient failures and greater and greater problems. In your garden things could be different, or very similar, with over application of dolomite lime creating a magnesium problem, or an over application of compost/manure creating phosphorus or potassium imbalance achieving the same situation. Poor nutrient availability to the plant leads to poor plant health leads to disease and insect attack and a low quality nutrient poor product.

In my own garden space I had just this case. A slightly high pH with a soil mineral matrix that included naturally excessive magnesium and potassium, little calcium and several years of over zealous applications of manure and compost that intensified the imbalance. It was the perfect situation for induced plant stress, low quality vegetables and rampant weed problems… much to my dismay. Had I followed the conventional thinking, organic or not, a little bit of sulfur would have been applied along with more compost. Net result would have been an ever worsening change in the soil, including increasing soil compaction and no improvement whatsoever to produce quality.

What about the idea that certain plants prefer a soil within a particular pH range? For example blue berries are thought to prefer an acid soil of 5.5 to 6.5, alfalfa from 6.5-7.5 and corn and wheat from 6.5-7.0. Studies in plant nutrition and available calcium have shown the truth of the matter (Soil Acidity as Calcium (Fertility) Deficiency Albrecht), when there is sufficient calcium for good growth then pH as low as 4.5 can grow a great crop. And since low pH soils are usually limed with calcium it erroneously leads one to think that pH makes a difference. Even the nitrogen fixing abilities of certain soil bacteria on legumes only works effectively when there is sufficient available calcium in the soil regardless of the pH.

Interestingly there is an alternative way to understand pH that makes a lot of sense. Recall from the last article I introduced the idea of positively charged ions called cations, and negatively charged ions called anions. What’s the importance of this? It’s that pH is a measurement of electrical resistance in the soil. Thus a pH reading of 7 means that there is an equal amount of resistance between the cation and anion charges. A high pH indicates there is too much electrical resistance in the soil, causing a restriction in energy-nutrient flow to the plant, while a low pH indicates that there is too little resistance causing an overload of energy-nutrient flow. Keep this idea in mind as in the future we will discuss this in more detail and how we can use electrical conductivity to monitor and improve upon plant nutrient uptake.

So instead of working to adjust your pH, it’s more essential to manage the factors that construct the soil pH. A very fertile soil for high nutrient and energy production is a living biological system and must must be carefully balanced for the needs of the soil microorganism via an equilibrium of pH, soil minerals, energy, physical conditions and organic substances. Without this balance, the potential for plant nutrition and soil building erodes.

Remember then, that pH is a consequence of soil nutrient and biological interactions, it is not a cause of anything. pH can however be a useful gauge for you to monitor how various nutrients and other substances you apply are interacting with your soil. It is not however to be used to determine what nutrient, mineral or compound to apply to the soil. That should only be done after you have carefully reviewed all the factors that contribute to excellent soil fertility.

~Sean

pH part I

If you’ve been following along with me you should well know by now my interest in growing high quality nutrient dense foods. Unfortunately food like that is a rare exception, both in the grocery store and at the farmers market. Before we can begin to discuss what that really means and how to achieve it, there are a number of ideas that all gardeners are taught that need some amending. I must first bring up the problem of pH.

Simply put, pH measures the concentration of hydrogen ions, where a low pH is called acidic and a high pH is called alkaline. A quick search on the internet for pH gave me a random University Extension Office document that says “Soil pH is important because it influences several soil factors affecting plant growth”. It goes on to inform the reader that it can do many bad things like preventing bacterial release of nitrogen, soilit can cause nutrient leaching or restricts availability of nutrients to plants, creates heavy metal toxicity and makes clay soil hard to cultivate. It goes on to say that “a pH determination will tell whether your soil will produce good plant growth or whether it will need to be treated to adjust the pH level.” Most importantly it gives you a solution to this insidious problem: add lime if your pH is below 6.5 and sulfur if it’s higher than 7. And if your one of those lucky fellows who’s soil is in the sweet spot of 6.5 to 7.0 then you don’t have to do anything at all. Sounds like pH is very important and according to this we certainly couldn’t have good plant growth without it.

That is the conventional approach to pH and anyone that knows me well can picture me cringing right now. The issue I have with this is that pH is treated like it has meaning unto itself. The soil is considered secondary to the pH. If this recommendation were followed up by your typical NPK soil test lab and their garden soil correction plan of applying composted chicken manure, it’s quite clear that attention is only indirectly given to plant nutrition. Following these recommendations is a shot in the dark. If you’re lucky your soil conditions may actually improve until you do the same thing again next year, but for many gardeners it can do precious little to improve “good plant growth” and can actually make things worse.

First we need to talk a little about what pH is. It stands for “power of Hydrogen”. pH is a scale ranging from extreme acidity starting from a score of 1, to extreme alkalinity and a maximum score of 14,  with 7 being the happy middle, the point of perfect balance. Water (H2O) separates easily into two ions with one of hydrogen (H+) and the other called hydroxyl (OH-). When these ions are in a one-to-one ratio you have a balanced pH of 7. If there are more hydroxyl ions (OH-) than hydrogen (H+) then the pH will be higher than 7, and if there are more hydrogen (H+) ions then the pH will be lower than 7. Thus, pH is a measure of hydrogen (H+) ions in solution.

This is however too simple to be useful. Hydrogen ions only cause soil acidity as measured by a standard test when they are in water, think of the water based test kits you see in the stores. In the soil, most hydrogen ions
beansare loosely attached to the soil particles along with many other positively charged ions called cations. These cations are there because of attraction to the negative charged particles, called anions. Anyways, these soil born hydrogen ions may not even contribute to soil pH unless the soil conditions change. Another interesting point is that as plants and microorganisms develop they will pull the plant nutrient ions, the cations, away from the soil particles and swap them out with additional hydrogen ions, thus causing the pH to drop during the growing season.

Materials you might consider adding to the soil to raise the pH are things considered to be alkaline such as calcium lime. However, this is relative to what might already be in the soil. For example calcium applied to a high magnesium soil may actually lower the soil pH. The same goes for acids, it’s relative. The  application of an acidic substance to the soil can actually further increase your pH, the wrong direction. Further, your soil could be desperately short in calcium, an essential plant nutrient, and have a high pH. In that case following the standard pH amendment procedure of not applying calcium lime would keep your soil in a very poor state and the healthiest weed growth yet.

Lastly, those that worry about pH will also state that too low a pH can release too much nutrients causing heavy metal toxicity or too high a pH can cause the locking down of the nutrients so they’re not available to the plants. This may be true in a sterile laboratory, but in a biologically active soil it’s quite different. Biological compounds interact differently than non-biologic compounds. For example, a high pH soil can be induced to release nutrients when organic humates, molasses and biochelates are used. One more thing, if you measure your soil pH on a weekly basis you will see it change throughout the year, this is at least partially due to increasing or decreasing amounts of microorganism activity.

Thus your soil pH score is the result of complex chemical, physical and biological interactions and doesn’t give any clues about what might actually be in your soil. Taking actions based only on this number is the surest way to limit the nutrient potential of your vegetables and induce plant stress. A pH reading however isn’t completely useless, in part II to this article I will elaborate further on this topic and how it can be a useful tool to growing great foods.

~Sean