Tuesday, January 20, 2015

A tale of two gardening methods

After my last post a gardening mentor contacted me with some suggestions on how I could improve my gardening practices (many thanks to my mentor!). As a result I’ve revisited the discussion on soil re-mineralization in Steve Solomon’s book The Intelligent Gardener (TIG), comparing it to the gardening method espoused by Ecology Action in the eighth edition of John Jeavons’ book How to Grow More Vegetables (HTGMV). In this post I’ll discuss what I’ve learned and how I will respond.

As part of my overall goal to grow a complete diet in a small area I have dedicated the last two years to developing a better understanding of my garden soil and its contribution to the goal. To do that I take soil samples at the end of the gardening season and have them analyzed for a range of major and minor nutrients and certain other parameters that affect crop growth. With the results from the analysis and using the information on soil mineral balancing in TIG I develop a plan to add organic fertilizers to the soil to address any deficiencies found by the soil test. By keeping track of how each crop that I grow fares over the course of the season and comparing that to how that crop fared before I began to re-mineralize the soil in 2013, I can determine what, if any, positive changes occurred as a result. I take the soil samples at the end of the growing season instead of shortly before it begins because my soil often does not thaw before early March, yet I should be planting spring crops as the month ends. Taking the samples in early March leaves insufficient time to prepare and mail them, have them run and receive the results, analyze the results to determine the soil prescription, and purchase and receive any needed fertilizers in time to add them to the earliest plantings.

The soil sample taken at the end of the 2014 gardening season shows calcium and magnesium at their target levels, compared to the deficiency of calcium and excess of magnesium found in early 2013 before two years of re-mineralization. In TIG Solomon notes that soil with a proper ratio of these two minerals has better structure. I felt that for myself when digging beds for the summer crops in 2014. Soil that had been quite sticky before is now easy to dig using an ordinary shovel and my middle-aged muscles. I can dig a 100 square foot bed in 1 1/2 hours versus around 4 hours before re-mineralization.

When my mentor contacted me I had worked out a fertilizer mix to re-mineralize in 2015. After sharing that information and the soil test results with him, he made some suggestions for my consideration. One of them was to add manganese sulfate to parts of the garden but not to others, to see if a deficiency in manganese relative to iron might be affecting certain crops.

The more important information he shared regarded nitrogen. As organic matter is eaten by the soil microorganisms, they release nitrogen in a form that plants can use. My mentor felt that many plants would grow better if they received more nitrogen than was present in the organic matter already in the soil and the compost and fertilizer mix that I had applied in 2014. Because I live in an area with hot summer days and nights, which leads to high microorganism feeding activity and rapid depletion of their food sources, the amount of cottonseed meal I included in the 2014 mix did not provide enough nitrogen for the needs of many crops. In 2013 I had added three quarts of cottonseed meal to each 100 square foot bed per the discussion in TIG. That at least doubled the amount of nitrogen available in each bed compared to using only compost, and yields increased in many cases. But I had been concerned about creating a dependence on imported nitrogen. In 2014, accordingly, I reduced the amount of cottonseed meal I added by 1/3, to two quarts per 100 square foot bed, while keeping the amount of home-generated compost constant. I noted that yields went down for many crops compared to 2013. My mentor suggested using four quarts of oilseed meal in the 2015 fertilizer mix as well as the 1/4 inch thick layer of compost that I normally add to keep nitrogen levels high enough for strong growth.

He also pointed out that because I have light soil (TCEC less than 10), meaning not much clay or humus present in the soil to hold onto the minerals that I apply to it, I might try side-dressing long season crops such as fall cabbage, tomatoes, sweet potatoes, and corn with another dose of the fertilizer mix every 6 weeks or so. TIG uses the analogy of clay and humus as the soil’s pantry. My light soil has a small pantry, insufficient to provide mineral meals to crops that remain at the dinner table for a long time. Occasional replenishing of the pantry will keep them growing strongly the whole season. Accordingly my mentor adjusted the quantities of soft rock phosphate and potassium sulfate for the 2015 fertilizer mix about 1/3 lower compared to what I had calculated. Lower-demand, short-season crops should still receive enough minerals to yield well. The long-season, higher-demand crops will get what they need with the extra dose of minerals and nitrogen from side-dressing. Assuming all else is equal, therefore, I hypothesize that by using the modified complete fertilizer mix on all beds and adding another dose to the long-season crops about 6 weeks or so into their season, yields of most crops, especially the long-season, higher-demand crops, should increase in 2015 versus 2013 and 2014.

HTGMV’s gardening method, which I had attempted to follow for over a decade, emphasizes growing grain crops in about 60% of the garden space. The grain crops provide two yields important to the method: the straw, which provides the carbon needed to produce enough compost to spread a layer 1/4 inch deep on the entire garden, and concentrated calories for the gardener, in the form of the seed grain. The grain crops, as well as special root crops that yield well and have a high amount of calories for their weight, form the backbone of a garden grown according to this method. HTGMV emphasizes this calorie gardening and its focus on increasing the weight per unit area obtained from these crops because of its concern with increasing human population and decreasing area of farmlands. Growing a higher yield on a smaller area addresses both of these concerns.

When I read the material on potassium in TIG, however, I began to wonder if HTGMV’s method might have a flaw that they do not acknowledge. TIG points out that the least expensive way to increase agricultural yields is to increase the amount of potassium in the soil relative to the other minerals that plants use. A potassium-rich soil can grow plants with high amounts of the carbohydrates, sugars, and fats that provide calories. However, other minerals are required to make the proteins, enzymes, and vitamins that we need for optimum health. In Solomon’s opinion, if potassium is just a little bit scarce relative to the other major and minor plant nutrients, the yield (weight per unit area) of the food grown will be somewhat reduced, but the plants will make the highest concentration of nutrients in proportion to the calories they contain. Hence he targets for less potassium relative to the other nutrients in order to grow nutrient-dense food. Nutrient-dense food, he feels, makes for healthier people, so he is willing to trade off some yield in order to grow the most nutrient-dense food that he can.

A goal common to both gardening methods is to build and maintain what each considers to be the proper levels of and balances among soil minerals. To do that you need to know what the levels of the various minerals are and, if they are not in balance, how to safely move them in that direction. Accomplishing this goal begins with collecting soil samples and sending them to a soil testing service. Gardeners often submit soil samples to their state extension service, but extension services typically provide only a restricted amount of information on the minerals in highest quantity. Thus both HTGMV and TIG recommend dedicated soil testing services for soil mineral analysis. Timberleaf Soil Testing, the soil testing service recommended in HTGMV, requires the purchase of two different test suites on each sample, the Basic Soil Test and Trace Mineral Soil Test, to obtain levels of all the minerals tested for by Logan Labs, the testing service recommended in TIG, at more than twice the cost of testing done by Logan Labs. The Basic Soil Test that you must buy from Timberleaf includes several other kinds of tests that are not mentioned in TIG or done by Logan Labs, one factor in the increased cost. Another part of the increased cost is accounted for by Timberleaf’s also providing some individualized information on what kinds and how much fertilizer to use to bring the soil into balance as well as individualized information related to the parameters they test for that Logan Labs does not. Logan Labs does not provide any soil information beyond the levels of the minerals, the soil pH, the organic matter level, and the TCEC, nor does it provide information on how to remedy the deficiencies in the cost of its basic test. However, someone who wants to follow the re-mineralization program in TIG but does not feel confident enough to convert Logan Labs’ soil test results into amounts of fertilizer to use to remedy deficiencies can subscribe to OrganiCalc at $9.50 per year to obtain that information. Put the cost of Logan Labs’ soil test and a one-year subscription to OrganiCalc together and you have still spent less money than the equivalent tests and information from Timberleaf.

HTGMV and TIG differ in the depth of their discussions of soil fertility and the range of potential materials with which to remedy patterns of deficiency and excess. The discussion of soil fertility in HTGMV is brief and sketchy, compared to the extensive and detailed discussion in TIG. HTGMV does not discuss what the target levels of each nutrient should be and that information is not provided on Timberleaf's website, while TIG discusses two different sets of mineral targets and why a gardener might choose one over the other. Further, compared to the wide range of potential nutrient sources given in TIG because of differing soil types and resultant patterns of mineral deficiencies and excess, HTGMV offers a very restricted range of nutrient sources to remedy deficiencies. Many organic fertilizers that were recommended in earlier editions of HTGMV are no longer recommended “because of potential problems with disease, pesticide residue, or heavy metal toxicity” (page 74). Unfortunately, that leaves out inexpensive and readily available sources of organic nitrogen such as oilseed meals and a wide range of fertilizers approved for organic farms to address differing soils and their needs. TIG acknowledges that oilseed meals from conventional farms may contain traces of pesticides and may be produced from genetically engineered seeds. All of us need to examine the various factors pertinent to each fertilizer material that might be appropriate for our soil and make the best choices we can from the limited information we have available. TIG prefers to offer a broader range of potential fertilizers, allowing us to weigh the choices involved and then make our own decision on what to use.

Suppose we find that we need to import a range of organic fertilizers and oilseed meal to up nutrient levels enough to grow nutrient-dense crops as described in TIG, or the more restricted range of fertilizers and nitrogen sources that HTGMV recommends to fulfill whatever its soil mineral target levels are. Both methods have as a goal importing the fewest resources from outside the garden and say that following their method will move garden soil in that direction over a period of years. Both methods have as a goal growing good yields of high-quality produce. Is there a basis for making a choice between them? I cannot give a definitive answer to that question although the discussion above highlights some of the factors that I think are relevant to that choice. As I’ve noted before, I only had one soil test done on my potential garden space in the decade I’d been gardening it before beginning re-mineralization. While I’d been following various aspects of HTGMV’s method, I had not done it as rigorously as they suggest; I never followed all the steps in the same year. I haven’t used Timberleaf’s soil testing services so I don’t know how its target levels and results might differ from Logan Labs’ and TIG’s. What I do know is that after over a decade of imperfectly following HTGMV’s method, yields were declining in many cases and none were increasing. Insect pressure and disease problems were increasing for some crops. After two years of following TIG’s method imperfectly (not giving long season crops sufficient nitrogen), insect and disease pressure has declined and yields have stayed the same or increased.

Ecological sustainability, a concept at the heart of HTGMV, needs to be understood in the broadest possible way. Focusing too intently on growing the most food in the smallest possible space as the answer to the problem of increasing human population and decreasing farmland area may not allow us to consider how everything interacts to produce that food and the impact that food has on our health. For instance, if we are producing less nutrient-dense food as a result of focusing excessively on increasing yield (weight per unit area), we may need to eat more of that food in an attempt to obtain the nutrients we need. If that’s the case, even if someone following TIG does not obtain as high a yield as someone following HTGMV, the latter may find she needs to increase the size of her garden in order to eat the same amount of nutrients as is produced by someone following TIG’s method on the same soil.

Considering the discussion above, I plan to optimize yield and nutrition by following TIG’s method as well as I can over the next several years. TIG suggests that as the soil minerals approach closer to the target levels, it might be possible to greatly reduce outside inputs while maintaining mineral levels and balance. After just two years I have been able to reduce additions of calcium and sulfur. As I learn how much it will be possible to reduce inputs to my own soil I will also gain enough information on yields obtained from this method to begin to sketch out minimum-area garden plans that will work for our soil and climate. And, of course, I’ll post what I learn here.

Discussions of garden methods have their place -- and so do concrete plans. In the next post I’ll discuss the concrete details of new tools, new procedures, and new crops for the 2015 garden.


  1. Hi Claire,
    Great post. Interesting that you are now getting a "feel" for the soil based on the results of the soil tests and observing what the differences are first hand. The digging example is a really good method.
    The nitrogen deficiency and experimentation is very interesting. I sometimes wonder if it takes a few months to a year for the soil organisms to simply make nitrogen in manures available for plants – it is certain that some minerals become readily available after application, but it is a slow process and is certainly not instantaneous. I'm unsure about this but in recent years I have been adding more manures with the composted woody mulches than previously and it is interesting to see what happens. It certainly speeds things up, but I reckon about 12 months is required before a tipping point is reached.
    That was very interesting too about the 1/4inch coverage of carbon mulch. As a comparison I go much harder and provide more than 1 and less than 2 inches of carbon heavy material - although that takes quite a while to break down (about 12 months here). It eventually forms a black sandy loam which virtually every plant thrives in - but it looks really ordinary for those first 12 months and as the woody mulch steals nitrogen from every source it really slows down. On the other hand I’ve started planting directly into it and stuff survives – although the plants are usually a bit stressed but when they take – wow and the eventual soil has masses of water and fungal hyphae in it.
    You are making me feel guilty for a generally more haphazard approach. I have a refractometer here and should probably test plants in different locations...
    Solomon is on the money by telling you how it is in relation to the heavy metals and toxic compounds in organic fertilisers. I struggle with that too, because I bring in vast quantities of woody mulches and manures and am pretty sure that there are all sorts of nasties in them. However having said that, by establishing fungal networks in your soil, my understanding is that those soils will eventually supply only the required minerals to the root systems of the plants in your growing area. Of course this is no guarantee, but what else do you do as we live in a world infused and saturated with toxic chemicals? Certainly the plant material grown here is much thicker than the shop bought stuff and I worry about the general mineral deficiency in the population.

    1. I think much of the difference in how thick a layer of mulch/compost we apply has to do with its woody or nonwoody character. I use a woody mulch on my herb bed, which is planted almost entirely to perennials, at about the same thickness (between 1 and 2 inches) as you use when you apply your woody mulch. I think it breaks down at about the same rate as you say yours does - maybe two years to mostly break down. On the separate vegetable garden, I use the compost from my compost piles, which ideally have no woody materials in them, just autumn leaves, garden weeds, and kitchen wastes. (Some twigs and branches get in there too because they get raked up with the leaves, but I remove as many as possible when I sift the compost.) The compost is much finer and in a fit state to be eaten rapidly by the microorganisms, so it doesn't need to be applied thickly in order to serve as a food source. Since I am doing a lot more digging in the vegetable garden (because the plants are annuals or biennials grown as annuals) it works better there to use compost rather than mulch. I mulch the perennial plantings and save the compost for the vegetable garden where it does the most good.

      Since the vegetable garden is getting dug each year it's not establishing much if anything in the way of fungal networks. That's something I have to accept as a given with that kind of management. I'm using conventional cottonseed meal that is almost certainly grown from genetically engineered seeds and grown using various 'cides. The fertilizers may be bringing in small quantities of heavy metals. Not much to be done for that. All that stuff is out there, being used to grow foods that I eat when we aren't eating homegrown food. Plus the rain and air bring in their own share of them. I do the best I can, as you do; we both try to make things better within the limited areas that we have some influence on.

      Speaking of fungal networks, when I planted goldenseal seeds into the developing food forest (nut and other trees) behind the vegetable garden, I could smell and see the mycelia in the soil! That was most heartening. When we moved here that was 10000+ square feet of mowed grass. All I did was plant and protect the trees. They did the rest. One of these days I'll write more about the bit of permaculture that I do.

  2. Exactly, the better established your soil is and the more access that that soil life has to various minerals as and when needed, the hardier your plants will be and the more resistant to pests/diseases. It really does make a huge difference.
    Spot on. You also have to begin to consider the needs of all of the life that exists in your gardening / productive space. There is a guy around this area that I know that has been producing food on his farm for over 30 years. And he's really good - some of the plants that I've gotten from him are excellent and he now obtains seeds from my place. However, he is also having problems with rusts and all sorts of other pest troubles because he fails to replenish the minerals that he extracts from his system. When you extract plants from your growing system, so too are you extracting minerals and all sorts of other stuff and that needs to be returned in some sort of cycle otherwise it has a finite end point. It can’t be gotten around except with applications of mineral fertilisers, mulches and manures. The old timers used to get around this problem by allowing plots to go fallow (ie. get really weedy – far more than we’d be comfortable with) for many years before ploughing and then replanting. The weeds accumulate minerals in their root systems which become available when those plants die. It is a massive and hideously complex loop and I'm only getting my head around this stuff very slowly. Many areas had historical mineral deficiencies in the food that they produced.
    Well done. I greatly respect your work. You do with science, what I do with observation.
    PS: The new coneflower (Echinacea) here seems to have taken this year.

    1. A huge part of science is observation! Back when I was going to college the first chemistry experiment we did was to make 50 observations on a burning candle. Its importance is to train us to do what you are doing. In my opinion you are doing science. You do it in a way that works for you and where you are. I have a formal background in chemistry and enjoy the opportunity to apply it in the wider world for a worthwhile purpose.

      You're right about managing for everything and everyone. We have a greater diversity of birds, insects, and amphibians now than when we moved here because of the increase in diversity of the plantings. People notice it when they visit our property and comment on how pleasant it is here.

      Glad to hear about the new Echinacea! Which species is it? I've planted four different species in the herb garden and at least three of them remain. The photo above shows either two or three of them (two of the species only differ in subtle characteristics such as pollen color). Echinaceas are among my favorite flowers.

  3. Well Claire, you are on the right track, but I suggest you think holistically rather than focusing on adding one nutrient or another. I go through this quite extensively in The Laws of Physics Are On My Side (2013) and I am a big fan of Solomon but not Jeavons. What I am doing now is using cover crops extensively to build organic matter (this includes weeds which I whack down, BTW), as well as green manure corps that transform insoluble phosphorous to soluble phosphorous (like buckwheat).

    You might also want to consider using indicator weeds to indicate the relative health of your soil. For instance, here on my farm thistles indicate low fertility, nightshade indicate middling fertility, and purple dead nettle indicates high fertility. I get more and more purple dead nettle every year. Since you are already using soil tests, a little observation should tell you which indicator weeds you can use. (BTW I don't use soil tests because of false positives and the feed-the-plant mentality behind them.)

    1. Thanks, Walter! Eventually I'll learn to read fertility from weeds and going by what they say. I don't expect fancy soil tests to be available and cheap for that much longer, but while they are and I am still learning about my soil, I think it is reasonable to make well-considered use of them. Plus as a chemist I understand their language.

      Speaking of indicator weeds, I'm getting more nightshade weeds in the garden than I used to. I'll have to look up purple dead nettle since I am not yet familiar with that weed by name, although it may be in my garden.

      I am working toward using cover crops much more than I am now. I didn't know buckwheat could transform insoluble phosphorus to soluble phosphorus; thanks for mentioning that! I'll make a note to try it where I don't have summer crops. And I found your blog and will read more of your work when I have time.

  4. Hi Claire,

    Exactly, herb beds tend to benefit from a good dose of woody mulch. Although these days, I'm now trying to accelerate all of the growing systems here by mixing the woody mulch with mushroom compost (which is really a fancy name for horse manure and bedding straw). It is sourced from racing stables so probably has quite a lot of anti-worming agents in them which will be a problem in the short term.

    As to not having woody materials in your compost piles - some plants such as tomatoes actually like a bit of carbon in their feed - but I did note in the previous post that your yields for that crop were good.

    Yeah, digging is definitely an issue with perennial beds - although the haphazard method of allowing annual plants in those perennial beds to self-seed allows them to establish their own life cycles and often they act like a recurring perennial plant. It is a different way of looking at those plants.

    Contamination is certainly an issue - here too, but what do you do? There really is no alternative and you are certainly better proceeding with your approach.

    It certainly does have its own smell. Yes, I'd be very interested to hear about that.

    My lady has a background in applied biology so that is a good help here too.

    It is great that people and all of the wildlife actively notice the difference at your place - that is a real credit to you.

    I think it was a purple cone flower - I don't believe that the plants have been in the country here that long – I believe a gardening club that I belong to brought them in – which is no easy feat here.

    Cheers. Chris

  5. Goodness, Claire (is that your first or last name we are referring to you by?) I am so impressed at your detailed analysis of Steve Solomon's work. I bought The Intelligent Gardener because Steve Solomon lives about twenty minute's drive away from me, and our soil and conditions are pretty much identical.

    But it is seriously the most difficult gardening book I have ever read! The salient points I got my head around - here in Tasmania we have nutrient depleted soils due to geographically old soil and high rainfall. We have plenty of potassium which makes our plants look green and healthy, but they are not high in other essential nutrients. So far I am with him, and the evidence is in the older, self-sufficient Tasmanians who suffer a lot of health problems, notably thyroid from lack of iodine in the soil. BUT then I lose him in the detail!

    What I have done so far is to start adding rock phosphates to increase mineralisation, and use more animal manures and lime and less mulch for our high rainfall area, and closely observing foliage for signs of mineral deficiency. I fully expect the process of really getting to know my soil to take years, but at least I have made a start..

    I will be interested to see how you get on. There is so much to take into consideration. I started out gardening so blithely thinking it was all about the planting, now I discover it is actually all about the soil..

  6. Hi, Jo! Claire is my first name. The SL refers to three different things, but I rather like a degree of anonymity on the internet, so I leave that to my readers to guess. Two of them can be gleaned from information in the blog for anyone who is so inclined. ;-)

    You're right, the book is highly detailed, and most people will find it difficult because it covers a lot of information they haven't been exposed to, or because it reminds them of a hated high school chemistry class or a hated math class. I had a big head start because I have degrees in chemistry. Steve made it as easy to grasp as he could (I doubt I could have done as well), and it is worth taking whatever time you need to study it carefully. It sounds to me like you are starting off well. I am trying to follow his advice to really GROW the plants, which means more careful observation on my part as well. So far, so good, but the growing season is young yet.