Before revision: While slopes along channels of 1:100 have been recommended, in practice it is difficult to build a base for channels that is sufficiently true to enable nutrient films to flow without ponding in locally depressed areas.
After revision: While slopes along channels of 1:100 have been recommended, in practice it can bethe occurrence of waterlogging and difficult to build a base for channels that is sufficiently true to enable nutrient films to flow without ponding in locally depressed areas.