Resumo

BARBIERI, Pablo A; ECHEVERRIA, Hernán E  e  SAINZ ROZAS, Hernán R. Economic optimal nitrogen rate for wheat as affected by fertilization timing in Southeastern Buenos Aires Province. Cienc. suelo [online]. 2009, vol.27, n.1, pp.115-125. ISSN 1850-2067.

Nitrogen fertilization in wheat is a common practice in the SE of Buenos Aires Province. However, there is a lack of local information to define the nitrogen (N) rate that responds to the maximum economic benefit. The objective of this work was to determine the economic optimal nitrogen rate (DOE) for genotypes of wheat (traditional or french) fertilized at sowing or tillering in this region. Two mathematic models were evaluated (quadratic and quadratic-plateau). Twentytwo N fertilization experiments from different sites (Otamendi, Balcarce, Mar del Plata y Tandil) and years (from 2002 to 2007) were used. The quadratic-plateau model produced the most rational results from an agronomic point of view because it gave lower DOEs than the quadratic model. Fertilization at tillering showed lower DOEs compared to fertilization at sowing. The difference in DOE between fertilization times was lower in french genotypes than traditional ones, and this difference would be explained by the greater N use efficiency determined in french genotypes. In french genotypes, the potential grain yield produced more variations in the DOE than the N- grain wheat price relationship. These results emphasize the importance of knowing the potential grain yield at the time of defining the DOE.

Palavras-chave : Wheat; Nitrogen; Economic optimal rate; Traditional and french genotypes.

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