The Availability of Fertilizer Nitrogen Immobilized During Decomposition of Straw

A greenhouse study measured the extent to which fertilizer N15immobilized during decomposition of straw becomes available for plants. Less than one‐half of the immobilized fertilizer N15was released for plant uptake during four successive croppings in the greenhouse. The crops were beets, barley, and two of corn. Fractionation of the soil N showed that about 75% of the N taken up by the plants was derived from the nondistillable acid‐soluble N fraction. Fertilizer N15immobilized in this fraction was utilized at a faster rate by plants than the N initially present in this fraction.