The world over, aged animal manure us revered for fertilizing gardens and farm fields. GETTY IMAGES

Bat guano or cow patties, aged manure is prized

The best gardening practices are the old ones, arrived at by observing processes already at work in nature, and steering them to the gardener’s advantage. They produce the best-tasting crops, with the safest and most economical use of resources. They contribute to the ongoing quality of the soil. They are easiest, because most of the work is done for you, by the sun, the rain and millions of creatures great and small that live in and around your garden.

Fertilizing with animal manure is one such technique. Thousands of years ago, gardeners observed that while grazing animals might improve the pastures with their droppings, animals confined to barns and paddocks produced a material that could then spread on cropland — with miraculous results. Seeds sprouted better, root systems were stronger, plants grew bigger and healthier, with higher yields. The Romans made ample use of manure in their agriculture; during the late Empire they built aviaries just to stockpile bird dung for this use.

Field crops and livestock go hand in hand. On traditional homesteads throughout the world, animals are kept not only for meat, milk and hides, but also for their excrement. The word manure, derived from the French words for “hand” and “work,” originally meant tillage, then done with hand tools. Later the sense narrowed to the act of amending the soil for greater fertility, and in present-day America it refers specifically to the dung of farm animals.

The era beginning with the domestication of the horse and ending with the domination of the horseless carriage was a great one for agriculture. (Imagine a form of transportation that produces a valuable natural resource.) The fabulous market gardens that once flourished near Paris owed much of their fame to ample horse manure from the city’s stables. Thomas Smith, writing in “French Gardening” in 1909, describes a soil that is entirely well-decomposed manure, “into which a walking-stick can be easily thrust to a depth of eighteen inches.” Soil quality like that is not achieved by spreading bags of 10-10-10. The manures of herbivores such as cows, horses and sheep are the ones most commonly used, and the product is simply the plants an animal eats, with their original package of nutrients largely intact, decomposed by a digestive tract and delivered along with a host of beneficial soil microbes in a handy slow-release form. In fields and forests, animal droppings continually enrich the soil in just this way. Garden compost is an imitation of this process, and it’s wise to include 10 percent to 20 percent manure in your compost pile.

Well-rotted manure also is spread directly on gardens. It should look dark and crumbly, without a manure smell. I apply it in fall, raking it lightly into the top several inches of the soil, then letting the frost break it up and mellow it. In spring the sun’s warmth wakes up the microbes and makes the nitrogen more available — just at the time my plants need that boost.

Gardeners tend to use of whatever manure they can find — if not from their own livestock then from whatever farm or stable is handy — but many have a favorite. I like horse manure because it’s nicely balanced and comes with a lot of bedding, preferably straw. (Sawdust or shavings take too long to break down). Bedding absorbs valuable urine as well and helps make the soil airy and moisture-retentive. Other gardeners swear by cow manure, which is freer from weed seeds, and the one most often sold in bags. Some seek out donkeys — their dung is well-decomposed because they chew their food slowly. Or llamas and alpacas who poop in tidy piles. Bat guano has purported super-powers. Elephant is awesome — if you can find it. (It’s a main ingredient in the popular “Zoo-Doo,” which the Woodland Park Zoo in Seattle portions out by lottery.) Rabbit droppings are famously rich in nitrogen but must be used with caution; if the manure is too fresh it can burn plants’ roots.

The same is true of bird manures, including that of chickens. Composting it thoroughly, or ordering bags of pre-rotted “Cockadoodle Doo” online will minimize that problem. But according to compost guru Will Brinton of Woods End Laboratories in Mt. Vernon, Maine, the high levels of phosphorous in bird dung are even more of an issue. Many soils now suffer, Brinton says, from “creeping phosphorous syndrome” — the effect of too much phosphate fertilizer. Ah, another man-made problem, one unknown to the 6th century Roman writer Varro, who awarded the dung of blackbirds and thrushes the highest praise. If a supply of either came my way I’d give it a try, but first I’d check my phosphorous levels with a soil test. A modern trick, but a good one.

Barbara Damrosch’s latest book is “The Four Season Farm Gardener’s Cookbook.”



Barbara Damrosch

Barbara Damrosch

Barbara Damrosch’s latest book is “The Four Season Gardener’s Cookbook.”

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