Sugarcane vinasse fertirrigation negatively affects leaf photosynthetic rates in soybean (Glycine max, Leguminosae)

Abstract

Background and aims: A large volume of vinasse is generated annually in Argentinean ethanol producing provinces. It has been proposed that vinasses could be used for sugarcane or soybean fertigation. However, basic research to know the effect of vinasse on soil, morphology and crop physiology is scarce in the Argentine northwest.
M&M: We provide data on the effect of diluted vinasse (1:1, 1:5 and 1:10 v/v) on photosynthetic CO2 assimilation in soybean plants grown under semicontrolled conditions (greenhouse).
Results: Maximum photosynthetic assimilation rate (Amax) was strongly affected by all vinasse dilutions. In the lowest dilution (1:1) the Amax decreased 35% while in highest dilution (1:10) a 15.9% decrease was observed. Changes in Amax were correlated with decreases in stomatal conductance, leaf nitrogen content (Nf) and total chlorophyll. Data of chlorophyll fluorescence show a decrease in Fv/Fm at 1:1 dilution, which indicate a photosystem II (PSII) stress.
Conclusions: We can conclude that the application of diluted vinasse affects gas exchange parameters and if it is used it should be done with dilutions 1:10 or higher. Long-term studies are essential to know the effect of vinasse on physicochemical and biological characteristics of soils as well as the probable accumulation of heavy metals in fertirrigated plants.