Uptake and use efficiency of N, P, K, Ca and Al by Al-sensitive and Al-tolerant cultivars of wheat under a wide range of soil Al concentrations

The impacts of acidic soils and Al toxicity on wheat nutrient economy have been scarcely researched under field conditions even though these soils are widely spread in wheat production areas around the world. The main objective of this study was to quantitatively evaluate the element (N, P, K, Ca and Al) economy of an Al-sensitive and an Al-tolerant wheat cultivar growing under different soil Al concentrations at field conditions. To reach this objective, two field experiments were conducted in an Andisol in Valdivia (39°47′18″S, 73°14′05″W), Chile. 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) with three replicates. At harvest, plant biomass was sampled and divided into 5 organ categories: ears, grains, blade leaves, stems plus sheath leaves and roots. The element content (N, P, K, Ca and Al) in each organ was measured to quantify element uptake and concentration, nutrient uptake efficiency (UPE) and nutrient utilization efficiency (UTE). Element uptake (N, P, K, Ca, and Al) was negatively affected by the increased soil Al concentration in above-ground and root biomass in both cultivars (R2 = 0.61–0.98, p < 0.01), although clear differences were found between cultivars. On the contrary, the impact of soil exchangeable Al on the plant element concentration was minor, showing weak associations with soil Al levels. However, the Al concentration in above-ground tissues of the Al-sensitive cultivar was an exception because it increased exponentially with the Al soil concentration (R2 = 0.96–0.99, p < 0.001). Nutrient uptake efficiencies, UPEs (N, P, K and Ca), were negatively affected by soil Al concentrations and were well described by linear equations in both cultivars (R2 = 0.58–0.98, p < 0.05), with notable differences between them. Both nutrient uptake (capture) and UPE were the traits that best explained above-ground biomass production (R2 = 0.82–0.99, p < 0.001, n = 20). Nutrient utilization efficiency, UTEs (N, P, K and Ca) responded more conservatively to the soil Al concentration, except for the Al sensitive cultivar under very high soil Al levels.

Research highlights
► The effect of Al toxicity on element (N, P, K, Ca and Al) economy of wheat Al-tolerant and Al-sensitive cultivars was quantitatively evaluated.
► Nutrient (N, P, K, Ca) uptake was highly affected by soil Al concentration in the Al-tolerant and Al-sensitive cultivars but showing clear differences between these genotypes.
► Nutrient concentration of above-ground and below-ground organs was almost not affected by soil Al concentration in both cultivars.
► Al concentration of aerial organs (including grains) increased exponentially with soil Al concentration.
► Nutrient uptake efficiency of cultivars was more sensitive than nutrient use efficiency under soil Al toxicity.
► The nutrient responses of the Al-tolerant and Al-sensitive cultivars to Al toxicity were quantitatively described by linear associations.