Mixture of cultivars: pilot field trial of an ecological alternative to improve production or quality of wheat (Triticum aestivum).
In a field study in La Plata, Argentina, mixtures of wheat cultivars were tested as an ecological alternative to pure culture, for producing either a higher grain yield and/or better grain quality (higher protein content). Wheat cv. Buck Pucará (BP) a modern high yielding cultivar, and Buck Cencerro (BC), an old low yielding cultivar, but with higher grain protein content, were grown in a replacement series at two nitrogen levels (0 or 90 kg/ha) and at a fixed density of 300 viable seeds m-2 for 5 different combinations (mixtures). Nitrogen application influenced total aerial biomass production, number of spikes m-2 and grain yield, but not the harvest index. Total aerial biomass production after ripening was similar in both cultivars, but BP had a greater grain yield. The mixture of 67% BP and 33% BC produced significantly more total aerial biomass than pure stands of either of the component cultivars. It also produced a grain yield similar to the best yielding cultivar (BP), with an improved grain quality (grain protein content) when no N fertilizer was applied. The mixtures showed a lower harvest index with a higher proportion of resources allocated to competitive structures (stems and leaves). Because of their lower harvest index none of the mixtures had a grain yield greater than that of BP. Without fertilizer the percentage of grain protein of all mixtures was higher than that of BP and similar to BC under pure stands. With nitrogen application, all mixtures showed a similar grain protein content. It is suggested that the use of mixtures of contrasting cultivars could be an ecological alternative to optimize crop production in low input agriculture.