Grain yield, above-ground and root biomass of Al-tolerant and Al-sensitive wheat cultivars under different soil aluminum concentrations at field conditions

Considering the importance of acidic conditions and Al toxicity in arable soils of Chile, 2 field experiments were conducted in the 2005-06 and 2006-07 growing seasons in Valdivia (39°47′18′′S, 73°14′05′′W), Chile in an Andisol. The objective of this experiment was to quantitatively evaluate the effect of different soil exchangeable Al levels on grain yield, and above-ground and root biomass of Al-tolerant and Al-sensitive wheat cultivars under field conditions. Treatments were a factorial arrangement of: i) two spring wheat cultivars (Al-sensitive, Domo.INIA and Al-tolerant, Dalcahue.INIA) and ii) five exchangeable Al levels (0–2.7 cmol(+) kg−1). The experimental design consisted of a randomized complete block design with three replicates. At harvest, grain yield, grain number, thousand grain weight and above-ground biomass were recorded. At the same time, root samples were taken with the pinboard monolith method. Afterwards root biomass, root length density and specific root length were measured. Both above-ground and below-ground traits showed a wide range of values (e.g., between 10 to 2618 g m−2 and between 8 to 117 g m−2, for above-ground and root biomass, respectively) under the soil Al concentrations used in this study. Al tolerant and Al sensitive cultivars showed different sensitivities to Al toxicity. Interestingly, linear associations were found between grain yield or above-ground biomass and soil Al concentration in Al-sensitive (R2 = 0.95 p < 0.001 and R2 = 0.90 p < 0.001, respectively) and Al-tolerant (R2 = 0.91 p < 0.001 and R2 = 0.88 p < 0.001, respectively) cultivars. Soil Al concentration was found to have a much lower effect on the harvest index. A close, and unique, association was found for both cultivars between grain yield and above-ground biomass (R2 = 0.98 p < 0.001). Root biomass also showed a linear relationship with soil Al concentrations in both Al-sensitive (R2 = 0.96 p < 0.001) and Al-tolerant (R2 = 0.77 p < 0.001) cultivars. Root traits showed good relationships with both grain yield and above-ground biomass.