need only half of the amount used to supply all the nitro-
may grow hay to sell to a neighbor and trade for some
gen needs in the first year. However, it is not uncommon
animal manure from the neighbor’s farm, for example.
to find farmers who are trying to build up high levels
Occasionally, formal agreements between dairy farmers
of organic matter actually overloading their soils with
and vegetable growers lead to cooperation on crop rota-
nutrients, with potential negative effects on crop quality
tions and manure application.
and the environment. Instead of reducing the amount of
Systems without animals. It is more challeng-
off-farm residue with time, they use a standard amount
ing, although not impossible, to maintain or increase
annually. This may lead to excess amounts of nitrate,
soil organic matter on non-livestock farms. It can be
lessening the quality of many plants and harming
done by using reduced tillage, intensive use of cover
groundwater, as well as excess amounts of phosphorus,
crops, intercropping, living mulches, rotations that
a potential surface water pollution problem.
include crops with high amounts of residue left after
harvest, and attention to other erosion-control prac-
Organic Matter Management on
tices. Organic residues, such as leaves or clean sewage
Different Types of Farms
sludges, can sometimes be obtained from nearby cities
Animal-based farms. It is certainly easier to
and towns. Straw or grass clippings used as mulch also
maintain soil organic matter in animal-based agri-
add organic matter when they later become incorpo-
cultural systems. Manure is a valuable by-product of
rated into the soil by plowing or by the activity of soil
having animals. Animals also can use sod-type grasses
organisms. Some vegetable farmers use a “mow-and-
and legumes as pasture, hay, and haylage (hay stored
blow” system in which crops are grown on strips for the
under airtight conditions so that some fermentation
purpose of chopping them and spraying the residues
occurs). It is easier to justify putting land into peren-
onto an adjacent strip. When you use off-farm organic
nial forage crops for part of a rotation when there is an
materials such as composts and manures, soil should
economic use for the crops. Animals need not be on the
be tested regularly to ensure that it does not become
farm to have positive effects on soil fertility. A farmer
overloaded with nutrients.
MAIntAInInG orGAnIc MAtter In sMALL GArdens
There are a number of different ways that home gardeners can maintain soil organic matter. One of the easiest is using lawn grass clippings for mulch during the growing season. The mulch can then be worked into the soil or left on the surface to decompose until the next spring. Leaves can be raked up in the fall and applied to the garden. Cover crops can be used on small gardens. Of course, manures, composts, or mulch straw can also be purchased.
There are a growing number of small-scale market gardeners, many with insufficient land to rotate into a sod-type crop. They also may have crops in the ground late into the fall, making cover cropping a chal enge. One possibility is to establish cover crops by overseeding after the last crop of the year is well established. Another source of organic materials—grass clippings—
is probably in short supply compared with the needs of cropped areas but is still useful. It might also be possible to obtain leaves from a nearby town. These can either be directly applied and worked into the soil or be composted first. As with home gardeners, market gardeners can purchase manures, composts, and straw mulch, but they should get volume discounts on the amounts needed for an acre or two.
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Building SoilS for Better CropS: SuStainaBle Soil ManageMent