{"id":1285,"date":"2016-04-20T18:17:29","date_gmt":"2016-04-20T18:17:29","guid":{"rendered":"http:\/\/tobyhemenway.wpengine.com\/?p=1285"},"modified":"2016-04-28T19:07:39","modified_gmt":"2016-04-28T19:07:39","slug":"permaculture-cover-crops","status":"publish","type":"post","link":"https:\/\/tobyhemenway.com\/1285-permaculture-cover-crops\/","title":{"rendered":"A Permaculture Guide to Choosing Cover Crops"},"content":{"rendered":"

One of my constant refrains is \u201cPermaculture is a decision making tool for arriving at regenerative solutions.\u201d Here I\u2019m going to show how permaculture can help create strategies for deciding what cover crops to use. In permaculture, we\u2019re always looking for potent leverage points, and soil-building is a big one. If we create fertile, water-absorbing, biology-rich soil, a lot of higher-level problems\u2014things like insect damage, low nutrition, poor growth, and excess water use\u2014all go away. And cover cropping, which is the use of specific plants to add organic matter and nutrients, is a great way to build soil. I use other methods, such as composting and nulching, but there\u2019s something about having living roots in the soil that makes cover cropping extra effective. That thick network of roots is constantly exuding sugars and other microbe food, creating a life-rich rhizosphere that pumps nutrients into plants and builds a lush habitat for mycelium and other beneficial organisms.<\/p>\n

I\u2019m going to use cover cropping to illustrate how permaculture decision-making works. How do we design a cover cropping program? Good design has three major components: setting a goal, developing strategies, and choosing techniques. First, we already have our goal: We want to build our soil\u2019s fertility, organic matter, and tilth. There are many strategies for reaching this goal. (A strategy is simply a plan, or, as management consultant Henry Mintzberg puts it in my favorite definition,\u00a0a strategy is a pattern in a stream of decisions<\/em>) Different strategies for soil building include composting, sheet mulching, chemical fertilizers, organic fertilizers, cover cropping, and several more. It may seem like those are techniques rather than strategies, but I think of them as strategies because there are so many different ways of doing each. Do any two people build a compost pile in the same way? And we have many different kinds of cover crops, and a host of ways to use them. That\u2019s why I think of each of those as a strategy: Just because we\u2019ve arrived at cover cropping as a way to build soil, we\u2019re not done with making decisions. There\u2019s a \u201clower\u201d or more fine-grained level that we need to make some choices about. We need to choose the specific variety of cover crop, how and when we will plant, and how we will get that cover crop into the soil, such as by tilling, chop-and-drop, or harvesting and composting it. So we need to have some criteria in mind to help us make those decisions. That\u2019s one of permaculture\u2019s strong points: It gives us tools that remove a lot of uncertainty from making decisions. That lets us rest in the near-certainty that we\u2019ve made appropriate choices.<\/p>\n

To start that decision-making process, we first gather up information about cover crops\u2014we make lists. The first obvious list to make is simply a compilation of all the varieties of cover crops that can grow in our conditions. A little Googling will get us there. One of my top sources of cover crop information is Peaceful Valley Farm Supply (https:\/\/www.groworganic.com<\/a>). They \u2018ve got a huge assortment. But a simply list of cover crop species doesn\u2019t get us very far. We need to break it down into some categories, because we can\u2019t just plant any old cover crop; every soil has specific needs and conditions. Fortuitously, the drop-down menu on cover crops at the above link has already done some category-making for us. They\u2019ve divided cover crops into fall-planted or cool-season types, warm-season types, and year-round varieties. These categories give us a handy machete to begin chopping our way through the cover-crop thicket.<\/p>\n

What other categories will be useful in choosing cover crops? Another big dividing line is between plants that fix nitrogen and those that don\u2019t. Nitrogen-fixing cover crops are varieties that have a symbiotic relationship with specialized bacteria that can take gaseous nitrogen from the air, which plants can\u2019t use, and transform it into nitrate, nitrite, or ammonia, which plants can take up as fertilizer. Non-nitrogen fixing cover crops are important too. They build biomass and add carbon to the soil, which feeds beneficial soil organisms, helps retain moisture, lightens and fluffs heavy soil and\u2014oh, right\u2014alleviates climate change by pumping carbon dioxide out of the air and storing the carbon in the soil. Most cover crop blends contain a mix of N-fixers and non-N-fixers.<\/p>\n

A third division, near and dear to permaculturists, is that between annual and perennial cover crops. Annuals are great if we\u2019re going to till in the cover crop or follow the cover crop with something else. But there\u2019s a role for perennials, too, in paths or between rows of production crops, or as a constant biomass source. In a perfect world, all gardeners and farmers would be generating their own fertility on-site, not importing it from somewhere else that might be impoverished by the constant drain of organic matter. Ecological garden guru John Jeavons says that we should be dedicating roughly four to six times the area of our food garden to fertility crops to cover what we withdraw from harvesting. Before the fossil fuel era, most farms allotted more land for fertility production in the form of pasture for generating animal manure than they did for food production.<\/p>\n

We could come up with other categories, such as soil preference (clay, silt, sand), frost hardiness, and so forth, but the three I\u2019ve outlined above are the ones I use most often. Those categories create a two-by-two-by-two matrix or three-dimensional chart that really helps to zero in on the right choices. Let\u2019s build that chart.<\/p>\n

USDA Cover Crops<\/h2>\n

Here\u2019s a table of over 100 useful cover crops, edited from a USDA list at http:\/\/plants.usda.gov\/java\/coverCrops?sort=comname<\/a><\/p>\n

Click to download the table below as a\u00a0PDF<\/em><\/a><\/strong><\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Scientific Name<\/th>\nCommon Name<\/th>\nPlant Family<\/th>\n<\/tr>\n<\/thead>\n
Amaranthus caudatus<\/td>\nfoxtail amaranth<\/td>\nAmaranthaceae – Amaranth family<\/td>\n<\/tr>\n
Amaranthus cruentus<\/td>\nred amaranth<\/td>\nAmaranthaceae – Amaranth family<\/td>\n<\/tr>\n
Amaranthus hybridus \u00d7 hypochondriacus<\/td>\nPlainsman amaranth<\/td>\nAmaranthaceae – Amaranth family<\/td>\n<\/tr>\n
Amaranthus hypochondriacus<\/td>\nPrince-of-Wales feather<\/td>\nAmaranthaceae – Amaranth family<\/td>\n<\/tr>\n
Arachis glabrata<\/td>\nrhizoma peanut<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Arachis hypogaea<\/td>\npeanut<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Avena sativa<\/td>\ncommon oat<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Avena strigosa<\/td>\nblack oats<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Beta vulgaris<\/td>\ncommon beet<\/td>\nChenopodiaceae – Goosefoot family<\/td>\n<\/tr>\n
Beta vulgaris ssp. cicla<\/td>\nchard<\/td>\nChenopodiaceae – Goosefoot family<\/td>\n<\/tr>\n
Brachiaria ramosa<\/td>\nsignalgrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Brassica hirta<\/td>\nwhite mustard<\/td>\nBrassicaceae – Mustard family<\/td>\n<\/tr>\n
Brassica juncea<\/td>\nbrown mustard<\/td>\nBrassicaceae – Mustard family<\/td>\n<\/tr>\n
Brassica napus var. napus<\/td>\nrape<\/td>\nBrassicaceae – Mustard family<\/td>\n<\/tr>\n
Brassica napus var. pabularia<\/td>\nSiberian kale<\/td>\nBrassicaceae – Mustard family<\/td>\n<\/tr>\n
Brassica nigra<\/td>\nblack mustard<\/td>\nBrassicaceae – Mustard family<\/td>\n<\/tr>\n
Brassica rapa var. rapa<\/td>\nfield mustard<\/td>\nBrassicaceae – Mustard family<\/td>\n<\/tr>\n
Bromus hordeaceus<\/td>\nsoft brome<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Cajanus cajan<\/td>\npigeonpea<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Camelina sativa<\/td>\nfalse flax<\/td>\nBrassicaceae – Mustard family<\/td>\n<\/tr>\n
Canavalia ensiformis<\/td>\njack bean<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Carthamus tinctorius<\/td>\nsafflower<\/td>\nAsteraceae – Aster family<\/td>\n<\/tr>\n
Chenopodium quinoa<\/td>\nquinoa<\/td>\nChenopodiaceae – Goosefoot family<\/td>\n<\/tr>\n
Cicer arietinum<\/td>\nchick pea<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Cichorium intybus<\/td>\nchicory<\/td>\nAsteraceae – Aster family<\/td>\n<\/tr>\n
Crotalaria juncea<\/td>\nsunn hemp<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Cucurbita<\/td>\ngourd<\/td>\nCucurbitaceae – Cucumber family<\/td>\n<\/tr>\n
Cyamopsis tetragonoloba<\/td>\nguar<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Daucus carota var. sativus<\/td>\ncarrot<\/td>\nApiaceae – Carrot family<\/td>\n<\/tr>\n
Echinochloa crus-galli<\/td>\nBarnyard grass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Elymus hoffmannii<\/td>\nRS wheatgrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Elymus trachycaulus<\/td>\nslender wheatgrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Eragrostis tef<\/td>\nteff<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Eruca vesicaria ssp. sativa<\/td>\nrocketsalad<\/td>\nBrassicaceae – Mustard family<\/td>\n<\/tr>\n
Fagopyrum esculentum<\/td>\nbuckwheat<\/td>\nPolygonaceae – Buckwheat family<\/td>\n<\/tr>\n
Glycine max<\/td>\nsoybean<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Helianthus annuus<\/td>\ncommon sunflower<\/td>\nAsteraceae – Aster family<\/td>\n<\/tr>\n
Hordeum<\/td>\nbarley<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Hordeum pusillum<\/td>\nlittle barley<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Hordeum vulgare<\/td>\ncommon barley<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Indigofera hirsuta<\/td>\nhairy indigo<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Lablab purpureus<\/td>\nhyacinth bean<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Lathyrus sativus<\/td>\nwhite pea<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Lathyrus sylvestris<\/td>\nflat pea<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Lens culinaris<\/td>\nlentil<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Lespedeza capitata<\/td>\nroundhead lespedeza<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Linum usitatissimum<\/td>\ncommon flax<\/td>\nLinaceae – Flax family<\/td>\n<\/tr>\n
Lolium perenne ssp. multiflorum<\/td>\nItalian ryegrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Lolium rigidum<\/td>\nWimmera ryegrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Lolium temulentum<\/td>\nDarnel ryegrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Lotus corniculatus<\/td>\nbird’s-foot trefoil<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Lotus tenuis<\/td>\nnarrowleaf trefoil<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Lupinus<\/td>\nlupine<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Lupinus albus<\/td>\nwhite lupine<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Lupinus angustifolius<\/td>\nnarrowleaf lupine<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Medicago littoralis<\/td>\nwater medick<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Medicago lupulina<\/td>\nblack medick<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Medicago polymorpha<\/td>\nBur clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Medicago rugosa<\/td>\ngama medic<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Medicago sativa<\/td>\nalfalfa<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Medicago scutellata<\/td>\nsnail medick<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Medicago truncatula<\/td>\nBarrel clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Melilotus alba<\/td>\nwhite sweet clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Melilotus officinalis<\/td>\nsweetclover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Mucuna pruriens<\/td>\nvelvet bean<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Onobrychis viciifolia<\/td>\nsainfoin<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Panicum miliaceum<\/td>\nproso millet<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Pennisetum glaucum<\/td>\npearl millet<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Phacelia tanacetifolia<\/td>\nlacy phacelia<\/td>\nHydrophyllaceae – Waterleaf family<\/td>\n<\/tr>\n
Pisum sativum<\/td>\ngarden pea<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Poa pratensis<\/td>\nKentucky bluegrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Psathyrostachys juncea<\/td>\nRussian wild rye<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Puccinellia distans<\/td>\nweeping alkaligrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Puccinellia nuttalliana<\/td>\nNuttall’s alkaligrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Raphanus sativus<\/td>\ncultivated radish<\/td>\nBrassicaceae – Mustard family<\/td>\n<\/tr>\n
Secale cereale<\/td>\ncereal rye<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Sesbania bispinosa<\/td>\ndunchi fiber<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Sesbania herbacea<\/td>\nbigpod sesbania<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Sesbania sesban<\/td>\nEgyptian river hemp<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Setaria italica<\/td>\nfoxtail millet<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Sinapis alba<\/td>\nwhite mustard<\/td>\nBrassicaceae – Mustard family<\/td>\n<\/tr>\n
Sorghum bicolor<\/td>\nsorghum<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Sorghum bicolor \u00d7\u00a0S. bicolor var. sudanense<\/td>\nSudex (Sorghum-sudangrass)<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Sorghum bicolor var. bicolor \u00d7 bicolor var. sudanense<\/td>\nSudex<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Spinacia oleracea<\/td>\nspinach<\/td>\nChenopodiaceae – Goosefoot family<\/td>\n<\/tr>\n
Thinopyrum intermedium<\/td>\nintermediate wheatgrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Thinopyrum ponticum<\/td>\ntall wheatgrass<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Trifolium alexandrinum<\/td>\nEgyptian clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Trifolium ambiguum<\/td>\nKura clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Trifolium fragiferum<\/td>\nstrawberry clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Trifolium hirtum<\/td>\nrose clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Trifolium hybridum<\/td>\nalsike clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Trifolium incarnatum<\/td>\ncrimson clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Trifolium pratense<\/td>\nred clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Trifolium repens<\/td>\nwhite clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Trifolium subterraneum<\/td>\nsubterranean clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Trifolium vesiculosum<\/td>\narrowleaf clover<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Trigonella<\/td>\nfenugreek<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Triticosecale rimpaui<\/td>\ntriticale<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Triticum aestivum<\/td>\ncommon wheat<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Urochloa ramosa<\/td>\nbrowntop millet<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Vicia atropurpurea<\/td>\npurple vetch<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Vicia benghalensis<\/td>\npurple vetch<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Vicia faba<\/td>\nfava bean<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Vicia grandiflora<\/td>\nlarge yellow vetch<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Vicia sativa<\/td>\ngarden vetch<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Vicia villosa<\/td>\nwinter vetch<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Vigna radiata<\/td>\nmung bean<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Vigna unguiculata<\/td>\ncowpea<\/td>\nFabaceae – Pea family<\/td>\n<\/tr>\n
Vulpia myuros<\/td>\nannual fescue<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n
Zea mays<\/td>\ncorn<\/td>\nPoaceae – Grass family<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Next we need to organize these by dividing them up into our matrix. We\u2019ve got 3 categories and two choices in each category.<\/p>\n