How does organic agriculture, and especially cover crops, manage nitrogen efficiently?
Organic agriculture emphasizes building soil quality through the addition of organic matter. Among the benefits of such systems is a reduction of nitrogen loss from the soil. Organic systems supply nitrogen to crops in organic forms, such as those found in livestock manure and legumes and other plants used as cover crops—crops grown to cover the soil when cash crops such as grains are not growing—which act as “green manure” when incorporated into the soil. These organic forms of nitrogen are part of proteins and other large molecules (in contrast to most reactive forms of nitrogen, which are small inorganic molecules). Organic nitrogen is often slowly broken down by microbes in the soil into smaller forms—especially inorganic forms—that can be utilized by crops. Cover crops are especially important for improving NUE because they can also remove excess reactive nitrogen from the soil. In particular, they are usually grown when the cash crop is absent—from fall through winter—when cash c
