Predicting yield loss due to interference from two weed species using early observations of relative weed leaf area.

Experiments were conducted on linseed Linumusitatisson L.) and autumn-sown field bean (Vica faha L.) to test how well the relative leaf area-based yield loss prediction model of Kropft & Spitters could estimate yield loss due to interference from Stellaria media L. (common chickweed) or barley (Hordeum vulgare L.) alone or a combination of both S. media and barley. Damage coefficients were calculated for all comparisons. Generally, the model provided a better estimate of yield loss due to interference from barley than from S. media because of both the variability m crop yield response stemming from S. media's plasticity and the generally minor crop yield response to S. media interference. The addition to the model of a parameter accounting for asymptotic yield loss was, generally, not warranted for either S. media or barley in the single-weed species data sets. When both S. media and barley were present as weed species in the crop, the model that titled the data best for six out of 10 data sets was the one in which a separate damage coefficient was included for both species. There was no evidence that the presence of S. media influenced damage coefficient values for barley. However, in the presence of barley a parameter accounting for asymptotie yield loss was warranted for S. media in the two-weed species model. The combination of the addition of this parameter and the presence of barley affected the values of the damage coefficients for S. media in the two-weed species compared with the single-weed species models. Consequently, it was shown for these two weed species that two-weed species yield loss prediction models parameterized using data from single-weed species experiments generally resulted in different estimates of yield loss in comparison with models parameterized using data from two-weed species experiments. [ABSTRACT FROM AUTHOR]