Inorganic fertilizer and salt tolerance in Sorghum bicolor (L.) moench ssp. bicolor

Abstract

In many cases, increased salt tolerance has been shown to correlate with increased nitrogen (N) fertilizer in some plants. It was hypothesized that increased fertilizer would increase salt tolerance in Sorghum bicolor (L.) Moench ssp. bicolor (“milo”). In this study, three fertilizer treatments (containing 0, 50, and 150 lbs N acre⁻¹) and four salinity treatments (0, 40, 80, and 120 mM) were applied to S. bicolor. Weekly measures of chlorophyll concentration, height, stomatal conductance, and photosynthesis were conducted for 4 weeks of treatment. Biomass was measured following 4 weeks of treatment. Plant biomass, height, and chlorophyll concentration were reduced by increasing salinity. Any salinity of at least 40 mM reduced the height of plants, regardless of fertilizer concentration. Plant biomass was increased at 50 lbs N acre⁻¹ but was decreased at 150 lbs N acre⁻¹. Contrary to the hypothesis, increased fertilizer decreased many aspects of growth and performance in S. bicolor. There was a statistical interaction between salt and fertilizer for photosynthesis and stomatal conductance. Photosynthesis and stomatal conductance in 0 mM salt remained high across all fertilizer treatments, but were low across all fertilizer treatments in 120 mM salt. Photosynthesis and stomatal conductance in 40 and 80 mM salt treatments were high in low fertilizer concentrations and became lower in high fertilizer concentrations. This indicates that increased fertilizer does not always increase salt tolerance in crop plants and is indicative of a more complex interaction between plant and soil conditions.

Keywords:

• chlorophyll
• photosynthesis
• salinity
• salt tolerance

We thank the Department of Biological Sciences at Fort Hays State University for facilities and Mike Messeck for help in the greenhouse. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of interest statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data that support the findings of this study are available from the corresponding author, BRM, upon reasonable request.