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This article in AJ

  1. Vol. 83 No. 5, p. 864-870
     
    Received: May 14, 1990
    Published: Sept, 1991


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doi:10.2134/agronj1991.00021962008300050018x

Nitrogen and Dry Matter Accumulation, Remobilization, and Losses for Mediterranean Wheat during Grain Filling

  1. Despo K. Papakosta  and
  2. A.A. Gagianas
  1. Lab. of Agronomy, School of Agric., Aristotle Univ. of Thessaloniki, GR-54006 Thessaloniki, Greece

Abstract

Abstract

Dry matter and N accumulated by winter wheat (Triticum spp.) plants until anthesis are of importance under a Mediterranean climate because yield greatly depends on translocation of pre-anthesis assimilates to grain. This field study was conducted to assess the effect of N fertilizer and cultivar on the amount of pre-anthesis dry matter and N accumulated and remobilized, and the possible N losses. Two bread (T. aestivum L.) and two durum (T. durum Desf.) wheat cultivars were grown in a silty clay (Typic Xerorthent) in 1986 and 1987. Nitrogen at a rate of 150 kg ha−1 was applied before planting or 100 kg N ha−1 was applied before planting and then 50 kg N ha−1 at early boot stage. Cultivar dry matter translocation efficiencies ranged from 2.3 to 36.4%, N-translocation efficiencies from 60.9 to 80.7%, and the contribution of pre-anthesis assimilates to grain from 6 to 73%. Split N application reduced the contribution of pre-anthesis assimilates to grain. High amounts of N (>200 kg ha−1), which had accumulated by anthesis led to net N losses at maturity, even with high yields (>6 Mg ha−1). No N losses were observed when N content at anthesis was lower than about 150 kg ha−1. However, at values ranging between these upper and lower limits, N loss was yield dependent (only yields >8 Mg ha−1 prevented N losses). Split N application tended to reduce N losses. Results indicated that the greater the amount of dry matter and N accumulated before anthesis, the higher the translocation rates of dry matter to grain and the greater the risk of net N losses at maturity.

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