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Title: Evidence of nitrogen and potassium losses in soil columns cultivated with maize under salt stress

Author
item LACERDA, CLAUDIVAN - Universidade Federal Do Ceara (UFC)
item Ferreira, Jorge
item Suarez, Donald
item FREITAS, EMANUAEL - Instituto Federal De Educação Ciência E Tecnologia
item Liu, Xuan
item RIBEIRO, AURELIANO - Universidade Federal Do Ceara (UFC)

Submitted to: Revista Brasileira de Engenharia Agricola e Ambiental
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2018
Publication Date: 6/30/2018
Citation: Lacerda, C.F., Ferreira, J.F., Suarez, D.L., Freitas, E.D., Liu, X., Ribeiro, A.A. 2018. Evidence of nitrogen and potassium losses in soil columns cultivated with maize under salt stress. Revista Brasileira de Engenharia Agricola e Ambiental. 22(8):553-557. http://dx.doi.org/10.1590/1807-1929/agriambi.v22n8p553-557.
DOI: https://doi.org/10.1590/1807-1929/agriambi.v22n8p553-557

Interpretive Summary: Although irrigation is necessary to guarantee agricultural production in semiarid areas, it leads to salt build up in the soil. The aim of this work was to evaluate the soil accumulation of salts from irrigation water, and of N and K from fertilization. The experiment was conducted in PVC columns (20 cm in diameter and 100 cm in height), filled with sandy, non-saline, soil and cultivated with maize. Four levels of salinity, with electrical conductivity of irrigation waters of 0.5, 2.5, 5.0, and 7.5 dS m-1, and four rates of nitrogen were used, with five replications. Nitrogen was applied as urea, and potassium as potassium nitrate with the following rates: N1- N recommendation for maize (2.6 g column-1); N2 - 0.3 times (0.78 g column-1) the recommended N1 dose; N3 and N4 - reduced rate of N1 and N2 doses, respectively, based on the evapotranspiration reduction caused by salinity. After 74 days from sowing, the roots and soil samples were collected at different depths. The electrical conductivity of the saturated extract (ECe) and the concentration of ions from irrigation water (Ca2+, Na+, and Cl-) increased as a function of salinity and soil depth, while the mass of the root system decreased with salinity and soil depth. The increase in salinity also resulted in K+ and NO3- accumulation in the soil column, mainly in higher N rates (N1 and N3). At the end of the experiment, 88% of the NO3- applied at the highest salinity treatment (7.5 dS m-1) and the highest N rate (N1) was found beyond 20 cm from the surface of the soil, evidencing a fertilizer loss caused by leaching. These results are important to farmers and extension agents as they show that extra fertilizer applied during saline conditions are lost by leaching, representing a financial loss to the farmer and without any benefit for the maize crop.

Technical Abstract: The aim of this study was to evaluate the accumulation of salts in the soil from irrigation water and of N and K from fertilization. The experiment was conducted in PVC columns (20 cm in diameter and 100 cm in height), filled with non-saline soil, and cultivated with maize. A completely randomized block design in a 4 x 4 factorial was used, with four levels of salinity (0.5, 2.5, 5.0 and 7.5 dS m^(-1)), four N rates, and five replicates. Nitrogen was applied as urea and potassium nitrate at the following rates: N1: N recommendation for maize (2.6 g column(-1)); N2: 0.3 times (0.78 g column(-1)) the recommended N1 dose; N3 and N4 with N based on N1 and N2 doses, respectively, reduced proportionally based on the evapotranspiration reduction caused by salinity. After 74 days from sowing, root and soil samples were collected at different soil depths. The electrical conductivity of the saturated extract (ECe) and the concentration of ions (Ca^(2+), Na+, and Cl-) increased as a function of salinity and soil depth. The opposite was observed for the root system. The increase in salinity also resulted in K+ and NO3- accumulation in the soil column, mainly in treatments with higher N rates (N1 and N3). At the end of the experiment, 88% of the NO3- applied at the highest salinity treatment (7.5 dS m(-1)) and the highest N rate (N1) was below 20 cm soil depth, evidencing a N loss process caused by leaching.