Statistical modelling

Plant yield (grain yield)

We can likewise analyse grain yield and harvest index. From the analysis of variance for grain yield we can see that there is a significant difference between cultivars (P<0.001) and a significant but smaller difference among spacing levels (P<0.05). Again there are no significant interactions. If we were to include a contrast term for spacing we would find that the linear component is again significant (P<0.001). The relationship with cultivar, however, was opposite to that for biomass (see below).

The reason for Umtata having a higher grain yield may be that being determinate it is able to utilise its energy better and not waste it in growing in a vegetative way. Kranskop, on the other hand, may continue to grow in a vegetative way, even after reaching flowering stage, resulting in competition between leaves and seeds for nutrients and water.