A book review by Marina Bistrin.
The Intelligent Gardener – Growing Nutrient Dense Food by Steve Solomon, 2013.
The book is particularly relevant for those with clay soils.
How can you not pick up a book with that title?
In an intro by Erica Reinheimer, she repeats a famous aphorism, “Growth is controlled not by the total amount of resources available, but by the scarcest resource. Please let the scarcest resource be something like the gardener’s time, not some bit of mineral lacking in the soil.”
The author, Steve Solomon, now lives in Tasmania and has previously lived in various regions of the USA with totally different climatic and soil conditions. Throughout, he has been working out how to improve soil and has developed his own ‘Complete Organic Fertiliser’ that can be adjusted for various soil types. He also shows you how to read soil charts and interpret them for your conditions.
As I love compost, I was very impressed by the sections on composting and how to keep volume and nutrition in compost rather than letting it be off-gassed. To make nutrient rich compost, he adds clay and mature compost (an an inoculant) to the new compost heap, does not let it get too hot and does not add woody materials (such as cardboard or sawdust), which use up too much nitrogen in their decomposition. In many ways, nutrient-rich compost can be the simplest answer to most growing problems: for its water and nutrient-holding capacity, keeping soil structure open and friable, pH buffering and encouraging organisms in the soil such as worms etc and micro-life.
There are useful charts on such things as mineral availability with soil pH, lab test charts of soil minerals and the ways to interpret them, and even practical information on how to send soils to labs.
I feel this book should be called the dedicated and intelligent gardener, because the information on any one topic is scattered through the book (though he has chapters on various topics) so you need your notebook and pen handy.
Here is my precis of the general ideas in the book and what I understand from it.
- Minerals alter soil structure – its friability – especially calcium and magnesium. Magnesium and sodium tighten up soil to an airless structure limiting plant growth. . Gypsum has calcium in it and loosens up clay soils to make them more friable.
- pH alters minerals’ ability to dissolve, and so be available to plants (and microlife). There is a good graph of mineral availability at increasing pH. There are optimum pHs for growth of various plants.
- Clay and humus are vital to soil fertility, both to temporarily hold onto minerals and make them available for living organisms when needed, and as pH buffers (stabilisers). They stop minerals leaching out in the subsoil where plants cannot reach them, and stop them bonding into insoluble compounds where the minerals are unavailable for uptake by plant and animal life. Clay has a high Total Cation Exchange Capacity (TCEC). Clay attracts cations, (positively-charged ions), whereas humus is a good buffer of pH and attracts anions (negatively-charged ions). Clay is essential to humus formation, so humus is not easily formed in sandy seaside soils. The author’s definition of humus is “The resistant bits remaining after all the easy to rot stuff has rotted.”
- Mineral-rich compost is made with clay and compost addition – either a clay slurry and some fertile compost as an innoculant, or clay-rich loam soil. The author does not add woody carbon (rich materials such as paper, cardboard or sawdust) as this uses up nutrients in their decomposition. The heat of the compost should not exceed 57°C (if possible), with the hottest core temp not exceeding 68°C. Overheating kills nitrogen-fixing bacteria that can capture nitrogen in the pile. Carbon can escape by off-gassing as CO2, and other gases can escape, depleting the nutrition in the compost. Composting at lower temperatures gives more final volume. He only turns the pile once during decomposition and allows a 6-12 month period for the composting process. His target for compost percentage in garden soil is 7% in cold climates and 3.5% in hot climates (if irrigated). A clay percentage of compost is recommended at 1-2% starting volume or he adds about 5% loam soil (loam by definition contains clay and humus/compost).
- Calcareous (sandy) soils amendment: add clay to the compost to aid in humus development and sprinkle that compost onto the top layer of soil.
- Add ‘Complete Organic Fertiliser’ annually to your soil or mix in with the compost. After your soil has been amended, the only addition that you need to add is around 1/4 inch sprinkle of well-made rich compost over the top of the beds annually, plus his ‘Complete Organic Fertiliser’ (recipe below). His initial amendment of a new plot of land is 1 inch of enriched compost on top of the soil, or 2 inches half-rotted manure,. Allow time for that to be digested into the soil and you do not need to dig it in. Adding more organic matter than this is not necessarily better. There is a limit to how much organic matter you should add to your soil – more is not necessarily better.
Recipe for ‘Complete Organic Fertiliser’ (from page 84)
This is added to the compost before spreading usually or directly onto soil. This makes enough to cover 10 square metres.
- 3L of oilseed meal (or 2L oilseed meal plus 0.5L feather-meal and 0.5L fish-meal).
- 1L soft or colloidal rock phosphate, OR bonemeal.
- 1L kelp-meal and/or 0.5L azomite (for trace minerals), and/or apply liquid kelp fortnightly as foliar feed.
- Lime. If on forest land, add 0.5L ag lime 100# (fine grind) and 0.5L ag gypsum.
- Add 1/3 cup potassium sulphate.
Can also add 1 teaspoon borax, 1.5 teaspoon zinc sulphate, 2 teaspoons manganese sulphate and 1 teaspoon copper sulphate.
The author prefers ag lime to dolomite lime (which contains magnesium and tightens up the soil). He says that many Tasmanian farmers have been adding beach sand to their soil to make it more friable. The author has used ag lime and gypsum for the same purpose with success.