Abstract

DIVITO, Guillermo Adrián; ECHEVERRIA, Hernán Eduardo; BARBIERI, Pablo  and  SAINZ ROZAS, Hernán. Wheat foliar urea application at anthesis under water stress conditions. Cienc. suelo [online]. 2008, vol.26, n.1, pp.89-96. ISSN 1850-2067.

The foliar nitrogen (N) applications in the period from leaf flag to anthesis enable yield optimization and/or to improve grain quality, but can generate phytotoxicity that impacts negatively on both parameters. The aim of this work was to evaluate the effect of N rates, fertilization moments and the use of a urease activity inhibitor in foliar urea applications at anthesis under water stress conditions. The experiment was carried out during 2006 in Balcarce, Buenos Aires, in a wheat crop with 80 kg ha^-1 of diamonic phosphate applied at planting and 120 kg ha^-1 of urea applied at tillering. Three foliar N rates applied at anthesis (30, 40 and 50 kg ha^-1); three application moments (morning, mid-day and afternoon) and the addition or not of a urease inhibitor, n(n-butyl) thiophosphoric tiamide (NBPT), were evaluated in a randomized complete block design with a factorial arrangement of the treatments. A check treatment without N and without NBPT was included in the experiment. The wheat crop suffered water stress after the foliar application period. The application of increasing foliar N rates generated reductions in the greenness index (IV) values at 5, 8 and 14 days post fertilization (DPF). At 2 DPF, the addition of foliar urea caused reductions in the photosynthetically active radiation interception (RFAint) due to phytotoxicity effects (80 and 67% reductions for the check and fertilized treatments, respectively), but at 28 DPF fertilized treatments surpassed the check (55 and 40%, respectively), being the rate of 50 kg ha^-1 the one which intercepted the smallest proportion of radiation among fertilized treatments. Wheat yield and protein content of fertilized treatments were slightly greater than the check plots in spite of crop damage due to foliar fertilization coinciding with the critical period when yield is defined. Both parameters were not affected by the moment or rate of N fertilization although NBPT addition increased the yield slightly (4,027 and 4,141 kg ha^-1).

Keywords : Nitrogen; Urea solution; Phytotoxicity.

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