I thought I would take a crack at defining some commonly used terms around our farm. In an ongoing struggle to describe exactly what is the purpose of my business/passion, I find that these phrases get a lot of usage: calorie crops, carbon crops, and staple crops. I first encountered these terms and the concepts behind them through reading materials produced by John Jeavons’ Ecology Action of the Midpeninsula. Anyone familiar with Ecology Action’s work will be aware of these terms (primarily calorie crop and carbon crop) and the prominent role they play in Jeavons’ agricultural philosophy. Years ago, I came across a book written by Mr. Jeavons called How to Grow More Vegetables than you ever thought possible on less land than you can imagine. Unlike many books that take profoundly simple concepts and turn them into seemingly complex ideas by using lots of big, nebulous words, this book took profound ideas regarding the complexity of sustainable farming and presented them in clear, layman terms. This book along with other publications from Ecology Action have had a huge impact on my own personal farming philosophy. In turn, the terms calorie crop, carbon crop and staple crop each have broad applications but are relatively simple to define.
A calorie crop or “calorie-efficient” crop would be any vegetable that produces a large amount of food energy (calories) per unit of garden space. This would be specific root crops like potatoes, garlic, and parsnips, as well as perennial vegetables like Jerusalem artichokes. The primary concept here is that if you want to feed yourself and your family from your own garden you will not get there by growing only tomatoes, lettuce, and sweet corn. These may be grown in a way that make them healthy and more nutrient dense, but pound for pound there won’t be enough calories available to meet you or your family’s daily needs. You would have to eat 27 lbs. of lettuce to equal the number of calories in 1 lb. of potatoes. This seems simple enough, but another consideration in regards to raising more calorie crops in your garden, is that they tend to be heavy feeders. That is to say, they remove more from your soil than they are capable of giving back. Over cropping will rapidly deplete your soil’s fertility. This brings us to the second term, carbon crops.
A carbon crop or “carbon-efficient” crop would be any food plant that produces a large amount of carbonaceous material for the compost pile. This would include any grain like wheat, oats, upland rice, etc. and any seed crop like sunflowers. The primary concept behind carbon crops is that if you want to grow heavy feeders like potatoes and maintain healthy soil, you would need to add carbon crops to your rotation to help replenish the nutrients used by the heavy feeders. Many growers add cover crops like rye and clover into their rotation to help maintain soil fertility, but the added benefit to growing carbon crops, like grains, is that as a dual-purpose crop you are growing food for your soil and food for yourself. Grains can provide a significant amount of dietary calories in addition to your root crops. Regarding small-scale grain raising, I do intend to have some future posts detailing my experiences with these crops, from planting all the way through to harvest and low-tek processing. I would also highly recommend reading Gene Logdson’s book Small-scale Grain Raising.
The third term, staple crop, is not quite as simple to define as calorie crop or carbon crop, but it encompasses both. I would describe it this way, “any crop you would really want in your larder in the event of a national economic crisis like the Great Depression”. I am not advocating here for a survivalist mentality, but rather using the idea of a “national crisis” to set the framework for adequately determining what a staple crop is. If a national crisis were to happen, energy (gas, electricity, etc.) could be disrupted. Food that requires refrigeration would be a problem. The solution would be foods that can be preserved easily and stored without the requirement of electricity. Grains can be stored long term if properly dried. Root crops can be stored without electricity for many months in a cool basement or root cellar. Parsnips can simply be left in the ground in winter and dug as needed. These would be some of the staples you would depend on in a long term crisis.
Dry beans, while not classified as a calorie crop (root vegetables) or as a carbon crop (grains or seeds), do share similar characteristics. Dry beans are a good source of calories and nutrients, especially protein, and being nitrogen- fixing they can play a role in soil fertility management. Dry beans (Pinto, Navy etc.), require no electricity for long term storage. The soybean (not Edamame), is another type of bean that is nutritious, nitrogen-fixing, easy to store when dry, and has the added quality of its many diverse uses including soy milk, soy meal, and soy flour, and soybean oil, to name just a few. Dry beans would surely be a necessity in the event of a long-term crisis situation and are therefore classified as a staple crop.
To determine more clearly what is or is not a staple crop, you may want to consider the following criteria. Is the crop reasonably easy to grow in my region? Is it nutrient-rich and/or high in calories? Is it easy to harvest, process and store? Can it be effectively managed in a crop rotation to help maintain soil fertility? Can it be eaten raw, or cooked with minimal, if any, processing? These questions can be somewhat subjective based on your level of experience or the availability of specific processing and harvesting tools, but they can help in drawing up a further list of what is a staple crop. Such a list might include, peanuts, winter squash, and pumpkin seeds as well as nuts, fruits and berries.
Let me wrap up this little treatise by suggesting that these terms, calorie crops, carbon crops and staple crops, do not give us “new” ways to talk about sustainable food growing. What they really do is redirect our thinking back 50, 100, or even a 1000 years to a time when the farmer, the gardener, the homesteader thought about their food production in similar terms and would have asked themselves very similar questions.