Case study: The effect of wheat density and cultivar on growth and reproduction of burr medic (Medicago polymorpha L.), wheat growth, and yield
2022
Khan, Mubarak Ali | Shabbir, Asad | Mahmood, Zahid | Weiner, Jacob
We measured the effect of wheat density on weed biomass and seed production, wheat biomass, and grain yield in five wheat cultivars in Pakistan in the presence and absence of individuals of the weed Medicago polymorpha L. The presence of M. polymorpha decreased wheat biomass and grain yield by up to 25%, even though the density of the weed was low (5 plants m⁻²). When wheat density was increased from 130 to 390 plants m⁻², weed biomass and seed production were reduced by 68 and 85%, respectively, across all five cultivars. The average wheat yield increased by up to 7% with increasing density for all wheat cultivars. The cultivars varied in their responses to the weed and to their own density. While most effects were additive, there was a highly significant interaction between wheat density and cultivar on weed seed production, in which the cultivar that completely suppressed weed seed production at high wheat density was among the least suppressive at low density. The cultivar that produced the highest yield across all treatments was not among the best at suppressing the weed or producing biomass, suggesting that tolerance of weed biomass is also important at low but still damaging levels of weed infestation. Our results confirm that even a relatively low density of M. polymorpha can incur significant yield losses, but also show that it can be managed effectively with cultural practices like increasing seed rate and by selecting weed suppressive and tolerant cultivars suited to the local environment.
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