Uses and losses of nitrogen by maize and cotton plants under salt stress

ABSTRACT

There is no consensus on how much N can be applied to plants under salt stress. In our research we tested the hypothesis that such response depends on salt tolerance of the plant species. So, this study aimed to evaluate the uses and losses of N by cotton (salt-tolerant) and maize (moderately salt-sensitive) irrigated with waters of different electrical conductivity (0.5, 2.0, 4.0, and 6.0 dS m⁻¹) and fertilized with nitrogen (60, 100, and 140% of the recommended dose for each crop). We found that nitrogen doses beyond the recommended values exacerbated the negative effects of salinity on growth and photosynthetic rates, especially in maize plants growing under moderate to high salinity. N rates over the recommended dose did not increase leaf nitrogenous compounds, believed to attenuate the negative impacts of salt stress. Our results indicate that the responses to additional nitrogen fertilization depend on crop salt tolerance and on the level of saline stress imposed. Increasing N rates beyond crop needs under salinity only increased leaching losses and reduced the nitrogen-use efficiency, indicating that such practice would result in economic losses and environmental N overload, especially when a supplemental dose is applied to a salt-sensitive crop.

KEYWORDS:

• Salt tolerance
• nitrogenous compounds
• N-use efficiency
• Nleaching

Acknowledgments

Acknowledgments are due to the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Instituto Nacional de Ciência e Tecnologia em Salinidade (INCTSal), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), from Brazil, for financial support provided to this research. The authors are also grateful to Dennise Jenkins, from the US Salinity Laboratory, for the technical guidance in the development of the soil column model.

Disclosure statement

The authors declare no conflict of interest.

Additional information

Funding

This work was supported by the CNPq-Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq Proc. 307225/2015-1) and CAPES-Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Print/Capes/UFC-SCBA: 88881.311770/2018-01).