Abstract

PARRA-TERRAZA, S. et al. Nitrate/ammonium/urea proportions and potassium concentrations in the production of tomato seedlings. Rev. Chapingo Ser.Hortic [online]. 2010, vol.16, n.1, pp.37-47. ISSN 2007-4034.

The use of ammonia and urea as nitrogen sources in the production of seedlings for transplant is very limited due to lack of information and the potential risk of toxicity caused by these two forms of nitrogen. Therefore, the objective of this study was to evaluate the effect of four proportions of nitrate/ammonium/urea (100/0/0, 85/15/0, 85/0/15 and 85/7.5/7.5) and two concentrations of potassium (7 and 9 mol·m^-3) in the nutrient solution on growth and mineral composition of tomato seedlings produced in greenhouse. A completely randomized design with a complete 4x2 factorial arrangement of treatments with four replications was used. The growth data were taken 46 days after sowing and mineral concentrations were determined in leaves, stem and roots. The 85/0/15 proportion and 7 mol K⁺ m^-3 produced the largest stem diameter, while 85/7.5/7.5 with 9 mol K⁺ m^-3 yielded the largest root volume. The 85/0/15 proportion increased the stem/root ratio and fresh weight of seedlings 16.3% and 14.6%, respectively, relative to 100/0/0. The interaction nitrate/ ammonium/urea-K had a highly significant effect on the concentrations of nitrogen in leaves, stem and roots; of phosphorus in leaves and roots; of calcium and magnesium in roots. Replacing 15% of the total nitrate nitrogen in the nutrient solution with a similar percentage of nitrogen or urea or a mixture 7.5 % N-ammonia-7.5 % N-urea increased some quality parameters of tomato seedlings.

Keywords : Interaction; nutrient solutions; nutrient content; growth; tomato seedlings.

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