N and S dilution and stoichiometry in maize affected by N and S availability

CARCIOCHI, WALTER D.; PAGANI, AGUSTÍN; CIAMPITTI, IGNACIO A.

Congreso; ASA and CSSA Meeting; 2018

Nitrogen (N) and sulfur (S) dilution curves and their stoichiometry are useful tools to study nutrient status in maize (Zea mays L.). However, availability of these nutrients could affect the performance of these tools. Thus, the objective of this work was to study the effect of N and S availability on: i) N and S uptake (Nu and Su) dynamic, ii) N and S dilution curves, and iii) N/S ratio in maize. Seven maize field experiments were conducted in the Pampas Region of Argentina. Two factors were evaluated, N and S fertilization and their combination. Two N levels: i) no N (-N) and ii) N fertilization (+N) (from 100 to 200 kg ha-1) and two S levels: i) no S (-S) and ii) S fertilization (+S) (from 15 to 32 kg ha-1) were evaluated. Maize shoot biomass (W) and its N and S concentration were measured at different crop growth stages from sixth leaf (V6) to flowering (R1). The main outcomes from this study were: i) Su was delayed respect of Nu; ii) N x S interaction was observed in S dilution curve, as +N+S treatment presented a lower dilution rate than the rest of the treatments, while N dilution curve was only dependent on changes in N fertilization; iii) Su accounted for a larger proportion of variation on the N/S ratio relative to Nu. Additionally, N/S ratio was not stable during the crop growing season, decreasing with increasing W and varying with N and S availability. The results demonstrate that both N and S availability affect the nutrient concentration and uptake of each other nutrient for maize. Thus, when using S or N dilution curves or N/S ratio to characterize S or N maize status is necessary to consider the availability of the other nutrient, as a co-limiting factor.