Cover: A farmer in Nigeria irrigates vegetable crops during the long dry-season months. Sewage sludge and soil have previously been mixed by plowing. Just beyond this plot of young crops is a plot of older crops, showing that with sludge application and irrigation, farmers here engage in year-round farming. See Mbila et al., "Distribution and Movement of Sludge-Derived Trace Metals in Selected Nigerian Soils," p. 1667-1674. Photo by M. Mbila.