Nitrogen fertilization and growth retardants in wheat / Adubação nitrogenada e redutores de crescimento na cultura do trigo

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The objective of this work was to study the effects of nitrogen fertilization and growth retardants on wheat (Triticum aestivum L.) crop. The study was conducted at the Experimental Station Prof. Diogo Alves de Mello, Federal University of Viçosa, Viçosa-MG (2045 S; 4251 W; 650-m altitude), in 2005 and 2006. Three experiments were carried out in a randomized block design with four repetitions. In the first experiment, two wheat cultivars (BRS 210 and Pioneiro) were fertilized by two methods of N application (total dose applied at seed sowing or 20 kg ha-1 at sowing and the remaining as topdressing in the beginning of tillering), and five N doses (40, 60, 80, 100, 120 kg ha-1) in a 2X2X5 factorial design. The results showed that the cultivar Pioneiro had higher productive potential than cultivar BRS 210, however with lower lodging resistance; splitting nitrogen fertilization increased lodging and brought no benefit to grain yield; grain yield response to N doses was quadratic, reaching maximum at 96.8 kg ha-1, and produced linear increase in lodging of cultivar Pioneiro. The second experiment, with the cultivar Pioneiro, had factors arranged in factorial and hierarchical design with a control treatment. The treatments consisted of three growth retardants (chlormequat, trinexapac-ethyl and paclobutrazol) combined in three doses (500, 1000 and 1500 g ha-1 of chlormequat; 62.5, 125 and 187.5 g ha-1 of trinexapac-ethyl and 40, 80 and 120 g ha-1 of paclobutrazol) with two application times (Time 1 = growth stage 6 or Time 2 = growth stage 8 of Feeks and Large scale), and a control treatment lacking retardant application. There was no occurrence of lodging in any of the studied treatments. It was concluded that trinexapac-ethyl and chlormequat were efficient in reducing wheat plant height; paclobutrazol was not efficient in reducing plant height; chlormequat and paclobutrazol effect on plant height was independent of application time; trinexapac-ethyl applied at growth stage 8 produced more marked effects than when applied at the stage 6 of the referred scale; the increase in retardant doses produced lower plant heights; chlormequat doses and paclobutrazol had no effect on grain yield; the largest trinexapac-ethyl doses reduced yield. The third experiment was arranged in a 5X4 factorial design, consisting of a combination of five nitrogen doses (30, 60, 90, 120, 150 kg ha-1) with four doses of the growth retardant trinexapac-ethyl (0, 62.5, 125, 187.5 g ha-1). Lodging and height of plants increased linearly with increase of nitrogen doses and with reduction of trinexapac-ethyl doses. Grain yield decreased with the increase of trinexapac-ethyl doses in the treatments with 30 and 60 kg ha-1 N, gave quadratic response in the treatments with 90 and 120 kg ha-1 N and had linear increase with 150 kg ha-1 N. Increasing N doses produced quadratic responses of grain yield with 0, 62.5, and 125g ha-1 of trinexapac-ethyl and linear increase with 187.5 g ha-. The results led to the conclusion that the application of 0, 62.5, 125 and 187.5 g ha-1 of 1 trinexapac-ethyl allows the use of 83.46; 92.21; 100.95 and 150 kg ha-1 of N, respectively, and that 60 kg ha-1 N without trinexapac-ethyl produces the highest grain yield.

ASSUNTO(S)

yield triticum aestivum produtividade lodging of cultivar fitotecnia acamamento de plantas triticum aestivum

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