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

Authors: RIBEIRO, AURELIANO - Universidade Federal Do Ceara (UFC); LACERDA, CLAUDIVAN - Universidade Federal Do Ceara (UFC); NEVES, ANTONIA - Universidade Federal Do Ceara (UFC); SOUSA, CARLOS - Universidade Federal Do Ceara (UFC); BRAZ, REGIS - Centec - Technological Institute Education Center; OLIVEIRA, ADRIANA - Universidade Federal Do Ceara (UFC); PEREIRA, JORDANIA - Universidade Federal Do Ceara (UFC); Ferreira, Jorge

Submitted to: Archives of Agronomy and Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2020
Publication Date: 6/17/2020
Publication URL: https://handle.nal.usda.gov/10113/7019796
Citation: Ribeiro, A.D., Lacerda, C.F., Neves, A.L., Sousa, C.H., Braz, R.D., Oliveira, A.C., Pereira, J.M., Ferreira, J.F. 2020. Uses and losses of nitrogen by maize and cotton plants under salt stress. Archives of Agronomy and Soil Science. https://doi.org/10.1080/03650340.2020.1779228.
DOI: https://doi.org/10.1080/03650340.2020.1779228

Interpretive Summary: Although nitrogen (N) is believed to alleviate the adverse effects of salinity on crops, there is no consensus on how much N to apply to plants under salt stress. If unused by plants, excess N will lead to environmental pollution, increased salinity of soils and rivers, and financial losses by farmers. We wanted to know if plant response depended on the salt tolerance of the species and/or on the intensity of the salinity stress. We evaluated growth, physiological, and biochemical responses of cotton (salt tolerant) and maize (moderately salt sensitive) plants irrigated with different saline waters (0.5, 2.0, 4.0, and 6.0 dS m-1) and nitrogen doses (60, 100, and 140% of each crop recommended value). Our results showed that N doses beyond the recommended values increased the negative effects of salinity on plant growth and photosynthesis, especially on maize plants growing under moderate to high salinity conditions. Contrary to expected, application of high N rates did not result in the accumulation of nitrogenous compounds in leaves. In fact, N rates above the recommended dose for each crop increased N losses by leaching and reduced the efficiency of nitrogen utilization by plants, resulting in clear economic and environmental disadvantages. These results are important to extension agents, salinity researchers, and farmers dealing with saline soils and irrigation water in cotton, maize, and other crops. The technology generated in this work may bring considerable savings in N-based fertilizers, while preventing excess N from increasing salinity of soils and water resources.

Technical 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) plants irrigated with waters of different electrical conductivity (0.5, 2.0, 4.0, and 6.0 dSm-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 conditions. 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.