CHANGES IN YIELD COMPONENTS OF PLANTAGO-OVATA FORSK IN NORTHERN WESTERN-AUSTRALIA IN RESPONSE TO SOWING DATE AND SOWING RATE

A series of trials examined the response of yield components in Plantago ovata to environmental factors which altered the yeild potential of the crop. The factors examined were sowing rate and sowing date. Interpretation of these effects was based on a model of the relationships of individual yield components to final yield. The results indicated substantial compensation between spikes plant-1 and plants ha-1. As the sowing rate changed by a factor of four, there was a quadratic response by yield, giving a maximum reduction of 21% compared with the optimal sowing rate. Spike length and spikes ha-1 accounted for most of the changes in yeild. Seed weight, spike fertility and flower packing density were less affected. All yield components tended to vary together in the same direction as yield rather than show compensation effects as environmental suitability was altered.