Does an increase in available nitrogen during the seed-filling period improve soybean seed physiological quality under field water deficit?

ERGO, V.V.; GALLO, C.D.V.; SALVAGIOTTI, F.; CARRERA, C.S.

Rosario

Congreso; XXXIV Reunión de la Sociedad Argentina de Fisiología Vegetal; 2023

Sociedad Argentina de Fisiología Vegetal

Increasing or maintaining yield and seed physiological quality under water deficit (WD) conditions is challenging for agriculture under the current climatic change scenario. The aim of this study was to evaluate the increase in nitrogen (N) availability on seed physiological quality under WD during seed filling in soybean genotypes contrasting in seed protein concentration. We conducted a field experiment testing a high (42%, HP) and low (38%, LP) seed protein genotypes under irrigation and WD conditions (soil water content ≤ 25% of field capacity from R5, beginning seed filling) and two N levels: non-fertilized (N0) and fertilized (+N, 600 kg N ha-1 as fertilizer equally split at vegetative, beginning bloom, and beginning pod). At harvest seed physiology characterization (vigour, viability, and environmental and fracture damage variables) was determined by topographic tetrazolium test. Seed weight was also measured. The HP genotype showed higher seed weight (23%), viability (11%) and lower vigour (28%) than the LP genotype across water availability and N treatments. Under WD (regardless of N and genotypes), seed weight, vigour and viability significantly (p ≤ 0.05) decreased by 28, 14, and 20%, respectively; whereas seed damage due to environmental conditions was 35% higher compared to irrigation treatment. Independently of water availability and genotypes, +N treatment significantly (p ≤ 0.05) increased the vigour (14%) and decreased the viability (14%). The +N treatment also increased the fracture damage (40%), affecting the vigour but depending on the seed region damaged. Interestingly, we observed in HP genotype that +N × WD combination increased both, seed weight (14%) and vigour (61%). Although our results show that WD during seed filling produced severe damage in seed physiology attributes, the addition of +N mitigated this abiotic stress by increasing seed weight and vigour, mainly in the HP genotype.