Resumo

QUINTERO, César Eugenio et al. Nitrogen uptake and rice yield with different forms of nitrogen applied before irrigation. Cienc. suelo [online]. 2011, vol.29, n.2, pp.233-239. ISSN 1850-2067.

In Argentina, rice is mechanically sowed on dry soil and is then flooded from early tillering to maturity. This practice gives rise to conditions that promote nitrogen losses by volatilization and denitrification. The most recommended N fertilizers for rice have N in the form of ammonium or amides; however, nitric sources have shown advantages. A field trial was conducted to evaluate the responsiveness and absorption efficiency of different sources and forms of nitrogen. Urea, ammonium sulfate (AS), calcium nitrate (CN), solution of urea-ammonium nitrate-thiosulfate (UAN + ATS) and calcium ammonium nitrate (CAN) were tested. A fertilizer rate of 60 kg N/ha was applied before irrigation and a control treatment with no N was included. Rice N uptake and yield was measured. The control treatment yielded 9756 kg/ha and total N uptake was 137 kg/ha, while the fertilized treatments absorbed from 164 to 185 kg N/ha. Pure fertilizer sources (urea, SA, CN) showed a high rate of initial N uptake, with an 80 to 100% apparent recovery of N fertilizer at the panicle differentiation stage. Surprisingly, the greatest response was observed in the treatment with CN, presenting a high fertilizer use efficiency. The mixed sources (UAN+ATS, CAN) showed a lower N uptake and fertilizer recovery. The results of this field trial indicate that denitrification losses were not significant and nitric sources could be used in rice fertilization.

Palavras-chave : Rice; Nitrogen; Denitrification; Sources.

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