Slopes1
While slopes along channels of 1:100 have been recommended, in practice it can be difficult to build a base for channels that is sufficiently true to enable nutrient films to flow without the occurrence of waterlogging and ponding in locally depressed areas. As a consequence, slopes of 1:30 to 1:40 are sometimes used. This allows for minor irregularities in the surface. The slope may be provided by the floor, or benches or racks that hold the channels.
Flow Rates1
As a general guide, flow rates for each gully should be 1 litre per minute. At planting, rates may be half this, and the upper limit of 2L/min appears about the maximum. Flow rates beyond these extremes are often associated with nutritional problems.