DEAD FURROW - A narrow strip of soil (the width of a plow share) that has its plow layer excavated in the process of moldboard plowing but does not get filled in because it is on the outer edge of a field or a "land." Secondary tillage generally does not completely fill in a dead furrow, leaving a depression and often a zone of low fertility because of topsoil removal. Crops tend to yield poorly when planted in a dead furrow.
DENITRIFICATION - The process by which soil organisms convert dissolved nitrate to gaseous nitrogen under anaerobic (low-oxygen) conditions. This occurs when soils become saturated and results in losses of nitrous oxide (a potent greenhouse gas) and dinitrogen (N2, an inert gas).
DISKS - Rolling circular blades that have straight or fluted edges and are intended to cut residues, pulverize soil structure, and/or level the soil surface. Disks are often mounted in groups (gangs) of parallel blades. In a tandem disk harrow, leading and following disk gangs are mounted with opposite angles such that soil is first moved out and then back in. The amount of soil movement caused by disks is related to the angle of the disks, the down pressure on the disks, the design of the blade (straight or fluted), and the speed at which the disks are pulled. Single disks (coulters) designed to cut residues often precede other ground engaging tools in equipment designed for high residue conditions. Disks are often arranged and used to shape beds.
DRAFT - Power required to pull a draft tillage tool such as a plow or disk a specified distance. Draft implement - an implement that requires force to be dragged through the soil.
DRAFT IMPLEMENT - An implement that requires force to be dragged through the soil.
DRIFT - The physical movement of prohibited substances from the intended target site onto an organic operation or portion thereof.