Yield responsiveness in two- and six-rowed barley grown in contrasting nitrogen environments

Two- and six-rowed barley with different intrinsic ability to produce tillers and kernels per ear, would differ in responsiveness to nitrogen availability with environmental improvements. Two field experiments were carried out to elucidate how nitrogen supply (N-40 and N-150) affects yield and its components in two- and six-rowed barley. High nitrogen increased aboveground dry matter at anthesis, by improving cumulative solar radiation intercepted by the crop, determining an increased dry-matter production at maturity without changes in harvest index. In both barley types, variations in grain yield were explained by changes in kernels per unit land area rather than by differences in the average kernel weight. However, changes in the number of kernels were due to variations in the number of ears per m(2) in two-rowed barley and the number of kernels per ear in six-rowed barley. Ears per unit area showed a greater responsiveness in two- than in six-rowed barley due to a higher nitrogen supply treatment, associated with their intrinsic higher tillering capacity, while the number of kernels per ear was more responsive in six- than in two-rowed types. The fact that responses to nitrogen by the number of kernels per unit land area in two- and six-rowed barley is better explained by different yield sub-components, allows the speculation that the critical period for yield determination would differ between barley types.