DIAGNOSING SULFUR DEFICIENCY IN SPRING RED WHEAT: PLANT ANALYSIS

Abstract

Sulfur (S) availability indicators are necessary for rational fertilizer use. The goals were to assess the predictive capacity of: i) malate:sulfate ratio in leaf; ii) total nitrogen (N):S ratio in aerial biomass; and iii) total N:S ratio in grain. Six experiments were carried out in Argentina for two years. Between 90 and 100% of samples were correctly diagnosed by total N:S ratio during tillering, and critical N:S ratios varied from 14.8:1 to 16:1. At the same time, malate:sulfate ratio diagnosed correctly between the 35 and 65% of the samples. Grains with S deficiency were determined as those with a total S concentration lower than 0.15% and a total N:S ratio higher than 13.3:1. Validation of these new thresholds allowed determining that 77% of the samples were correctly diagnosed. A linear association between grain N:S ratio and N:S in aerial biomass during stem elongation was found (r² = 0.76–0.78, respectively).

Keywords:

• grain analysis
• N:S ratio
• malate:sulfate ratio
• diagnostic methods

ACKNOWLEDGMENTS

This work is part of a thesis submitted by Nahuel I. Reussi Calvo in partial fulfillment for the requirements for the degree of Doctor, Universidad Nacional de Mar del Plata (UNMP). This study was made possible with financial support of INTA (Project AERN 5656) and FCA UNMP (15/A261).