Hyperaccumulation of thallium is population-specific and uncorrelated with caesium accumulation in the thallium hyperaccumulator, Biscutella laevigata

Purpose

This study investigated the residual contribution of legume and fertilizer nitrogen (N) to a subsequent crop under the effect of elevated carbon dioxide concentration ([CO₂]).

Methods

Field pea (Pisum sativum L.) was labeled in situ with ¹⁵N (by absorption of a ¹⁵N-labeled urea solution through cut tendrils) under ambient and elevated (700 μmol mol^–1) [CO₂] in controlled environment glasshouse chambers. Barley (Hordeum vulgare L.) and its soil were also labeled under the same conditions by addition of ¹⁵N-enriched urea to the soil. Wheat (Triticum aestivum L.) was subsequently grown to physiological maturity on the soil containing either ¹⁵N-labeled field pea residues (including ¹⁵N-labeled rhizodeposits) or ¹⁵N-labeled barley plus fertilizer ¹⁵N residues.

Results

Elevated [CO₂] increased the total biomass of field pea (21 %) and N-fertilized barley (23 %), but did not significantly affect the biomass of unfertilized barley. Elevated [CO₂] increased the C:N ratio of residues of field pea (18 %) and N-fertilized barley (19 %), but had no significant effect on that of unfertilized barley. Elevated [CO₂] increased total biomass (11 %) and grain yield (40 %) of subsequent wheat crop regardless of rotation type in the first phase. Irrespective of [CO₂], the grain yield and total N uptake by wheat following field pea were 24 % and 11 %, respectively, higher than those of the wheat following N-fertilized barley. The residual N contribution from field pea to wheat was 20 % under ambient [CO₂], but dropped to 11 % under elevated [CO₂], while that from fertilizer did not differ significantly between ambient [CO₂] (4 %) and elevated [CO₂] (5 %).

Conclusions

The relative value of legume derived N to subsequent cereals may be reduced under elevated [CO₂]. However, compared to N fertilizer application, legume incorporation will be more beneficial to grain yield and N supply to subsequent cereals under future (elevated [CO₂]) climates.