The authors studied five fertilizer experiments with sweet potatoes conducted by the Instituto Agronômico, in which plots of four or five rows were separated by fallow strips much wider than the spacings used within the plots. In four of the trials the yields (per row) of the border rows were significantly higher than those of the inner rows, the average of the former being about 40% higher. In each experiment the relative border effect decreased as the yielding capacities of the plots increased, but this tendency was significant only in three cases and the correlation coefficients were low. The relative effects of the fertilizers used differed considerably in the inner and border rows; however, the observed differences were not significant.