Pedosphere 22(6): 785--794, 2012
ISSN 1002-0160/CN 32-1315/P
©2012 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Effect of combined use of brackish water and nitrogen fertilizer on biomass and sugar yield of sweet sorghum
T. B. RAMOS1, N. L. CASTANHEIRA2, M. C. GONCALVES2, M. L. FERNANDES2, M. I. JANU RIO1, M. E. LOURENCO3, F. P. PIRES2 and J. C. MARTINS2
1 CEER-Biosystems Engineering, Institute of Agronomy, Technical University of Lisbon, Tapada da Ajuda, 1349-017 Lisbon (Portu- gal)
2 Estacão Agronómica Nacional, L-INIA, Instituto Nacional de Recursos Biológicos, Quinta do Marquês, Av. República, 2784-505 Oeiras (Portugal)
3 Departamento de Fitotecnia, Instituto de Ciências Agr Árias e Ambientais Mediterrânicas, Universidade de Évora, Apartado 94, 7002-554 Évora (Portugal)
ABSTRACT
      Soil salinization and non-point source pollution are among the most important and widespread environmental problems in European Mediterranean regions. Sweet sorghum (Sorghum bicolor (L.) Moench var. saccharatum) is a moderate to high salinity tolerant crop with low water and nutrient needs, seen as an alternative to grow in the water scarce regions. A three-year multifactorial study was conducted in southern Portugal to evaluate the combined effects of saline water and nitrogen application on the dry biomass (total, stems, and leaves), sugar content (total reducing sugars and sucrose contents), and sugar yield (here defined as the product of total reducing sugars and stems dry biomass) functions of sweet sorghum. Sorghum dry biomass and sugar yield showed diminishing returns for each incremental change of nitrogen. The use of saline irrigation waters also led to yield reduction. Exception was sucrose content which increased with increasing levels of sodium in the soil. Nitrogen need decreased as the amount of sodium applied increased. Stem dry biomass, sucrose content, and sugar yield progressively increased with progress in the experiment. The effect could be attributed to the increase of the amount of irrigation applied throughout the years, thus increasing the leaching fraction which promoted salt leaching from the root zone, reduced the salinity stress, increased plant transpiration, nitrogen uptake and biomass yield.
Key Words:  Mediterranean conditions, non-point source pollution, salinity, sweet sorghum, yield functions
Citation: Ramos, T. B., Castanheira, N. L., GonÇalves, M. C., Fernandes, M. L., Janu rio, M. I., LourenÇo, M. E., Pires, F. P. and Martins, J. C. 2012. Effect of combined use of brackish water and nitrogen fertilizer on biomass and sugar yield of sweet sorghum. Pedosphere. 22(6): 785-794.
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