Autores: Javier D. Scheiner, Flavio H. Gutiérrez Boem, Raúl S. Lavado
Cátedra de Fertilidad y Fertilizantes, Facultad de Agronomía, Universidad de Buenos Aires
Trabajo presentado en: European Journal Agronomy 17 (2002) 73-79
 

In order to avoid nitrogen overfertilization, fertilizer rates must be adjusted to meet crop requirements. Two field experiments with sunflower (Helianthus annuus L.) were performed in the western part of the Pampas, Argentina, to: (i) assess nitrogen fertilization effects on seed yield, grain oil content, and plant lodging, (ii) determine N requirement per unit of yield, crop recovery of fertilizer N, and whether these two parameters were affected by N and other nutrient additions. Nitrogen fertilization increased the seed yield only by 17% at one site. Crop nitrogen requirement per unit yield (b-value) increased from 37 to 42 kg Mg−1 due to nitrogen fertilization only at the site where there was not a yield response. Therefore, if a yield response is expected, it is not necessary to use different b-values for non fertilized or fertilized crop. Reduction of seed oil content due to N addition was relatively small (2–5%), and was overcompensated by the seed yield increase at the responsive site. Recovery of fertilizer 15N was of 51%. This efficiency of absorption should be considered for making fertilizer recommendations. Application of further nutrients including P and K had no influence on seed yield. © 2002 Elsevier Science B.V. All rights reserved. Keywords : Sunflower; b-Value; Nitrogen fertilization; 15N recovery

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