The interaction of nitrogen and potassium nutrition on dry matter and nitrogen yields of the graminae: Spring wheat

Spring wheat was grown in three experiments in controlled environments. Various levels of N and K in factorial combination were given at sowing and at later stages of development. An ancillary experiment, also described here, showed that the main contribution to dry matter yield and N uptake after stem extension was from the ears, much of the latter being at the expense of the leaves and stems. Dry matter and grain yields at maturity reached a maximum at an (N/K)s atom ratio in the soil of between 2 and 2.5 (where N=total N given and K=total K given + exchangeable K in the soil). The relationships suggest that at (N/K)s values higher than the optimum, yields would decrease, as with perennial ryegrass (page 999). Comparing the relationships between grain yield g−‐1 N given and N given, and between grain yield and (N/K)s, shows the importance of balancing the K status of the growth medium (i.e. K given + soil exchangeable K) with N given. Split N and K combinations did not result in increased yields except at the highest levles and when given at or after anthesis (Feekes stage 10.5).