Yield Trends during Take‐all Decline in Spring Barley and Wheat Grown Continuously1

The effects of take‐all, nitrogen and cropping sequence on grain yield were compared for spring barley and spring wheat grown in extended monoculture. Initial crops showed least take‐all and maximum yields. Yields fell to a minimum more rapidly in wheat than in barley while the take‐all intensity increased to a maximum; take‐all decline occurred and yields improved from the 4th and 5th years respectively. Without nitrogen, yields were at their lowest level; application of nitrogen increased yields considerably with responses in proportion to the rate applied. At optimum rates, yield losses were 33% for wheat and 11% for barley with maximum disease intensity but only 9% and 3% respectively with take‐all decline. Potential maximum yields in the absence of take‐all were calculated to be greater with barley than with wheat.