Abstract

MACHADO, Rui Manuel de Almeida; ALPENDRE, Pedro Frazão; SHAHIDIAN, Shakib  and  JESUS, Ricardo Azevedo. Influence of nitrogen on onion growth before bulb initiation. Rev. de Ciências Agrárias [online]. 2012, vol.35, n.1, pp.88-95. ISSN 0871-018X.

The effect of nitrogen application prior transplanting on aboveground growth and root growth of the short- day onions (cv. Mineutaka), from transplanting to bulb initiation was studied in a pot experiment. The pot experiment was carried out with ten treatments, including two soil types (clay-sandy  and sandy soil) and five levels of N application (0, 10, 30, 40 and 50 kg N ha^-1) applied prior transplanting. Aboveground and root growth and biomass allocation (root: shoot ratio) were not significantly affected by nitrogen level or interaction nitrogen level * soil type. The residual soil inorganic N and the released N from organic matter, most nitrogen introduced by irrigation water (20 mg N plant^-1), was sufficient for plant growth before bulb initiation. Plant growth and biomass allocation were significantly affected by soil type. Plant biomass in clay-sandy soil was 30% higher than in sandy soil. Total root length of plants grown in sandy soil (43.74 m) was 2.3 times higher than in clay-sandy soil (19.26 m). Root biomass, specific root length (SLR) and root-shoot ratio were higher in plants grown in sandy soil.

Keywords : Allium cepa L.; biomass; nitrogen fertilizer; onion; total root growth.

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