Kernel chemical composition and flour quality of wheat in response to nitrogen sources and doses

The chemical composition of wheat kernels (Triticum aestivum L.) directly affects the quality of flour by modifying its functional and technological properties, determining its use by the industry. Field trials were conducted with wheat genotypes BRS 208 and BRS Pardela to evaluate the impact of different forms of urea (conventional, with urease inhibitor, and polymer-protected) and doses of nitrogen applied in topdressing (0, 40, 80 and 120 kg ha-1) in kernel chemical composition and flour technological quality. The experimental design was randomized block with 3x4 factorial structure, with four replications. The data were submitted to analysis of variance (ANOVA) with regression for nitrogen doses, and comparison of means for genotypes and forms of urea by Tukey's test (p≤0.05). Although the genotypes evaluated presented significant differences regarding kernel chemical composition and quality of flour, similar responses were observed for the variables evaluated, forms of urea, and doses of nitrogen. Application of urea with urease inhibitor increased starch content in the kernels, and polymer-protected urea reduced flour yield. A positive linear regression was observed between nitrogen doses and protein (R2=0.706) and ash (R2=0.990; p<0.01), and negative with lipid content (R2=0.836; p<0.01). However, the application of increasing doses of nitrogen reduced kernel volume density (R2=0.864; p<0.01) and brightness of flour (L*; R2=0.977; p<0.01). In addition to breeding, the application of adequate doses using various sources of mineral nitrogen could be used as an additional procedure to obtain raw materials with the desired chemical composition profile. Keywords. Grain quality, polymer-protected urea, Triticum aestivum L., urease inhibitor (NBPT) Resumo: A composicao quimica dos graos de trigo (Triticum aestivum L.) afeta diretamente a qualidade da farinha obtida, modificando suas propriedades funcionais e tecnologicas, determinando seu uso pela industria. Diante disso, experimentos a campo foram conduzidos com dois genotipos de trigo (BRS 208 e BRS Pardela) para avaliar o efeito de formas de ureia (convencional, com inibidor de urease e protegida por polimero) e doses de nitrogenio em cobertura (0, 40, 80 e 120 kg ha-1) na composicao quimica do grao e qualidade tecnologica da farinha de trigo. O delineamento experimental foi em blocos casualizados, esquema fatorial 3x4, com quatro repeticoes. Os dados foram submetidos a analise de variância (ANOVA), regressao (doses de nitrogenio), e comparacao de medias (genotipos e formas de ureia) pelo teste de Tukey (p≤0,05). Apesar dos genotipos avaliados apresentarem diferenca significativas em relacao a composicao quimica do grao e qualidade da farinha, ambos apresentaram respostas similares as variaveis avaliadas, formas de ureia e doses de nitrogenio. Aplicacao de ureia com inibidor de urease aumentou o teor de amido no grao, e a ureia protegida reduziu o rendimento de farinha. Observou-se regressao linear positiva entre doses de nitrogenio e teor de proteina (R2=0,706) e cinzas (R2=0,990; p<0,01), e negativa com o teor de lipidios nos graos (R2=0,836; p<0,01). Outrossim, a aplicacao de doses crescentes de nitrogenio reduziu o peso hectolitro do grao (R2=0,864; p<0,01) e luminosidade da farinha (L*; R2=0,977; p<0,01). Em adicao ao melhoramento genetico, a aplicacao de doses adequadas utilizando diferentes fontes de nitrogenio mineral pode ser recomendado como procedimento para obtencao de materia-prima de qualidade. -chave. Inibidor de urease (NBPT), qualidade do grao, Triticum aestivum L., ureia protegida por polimero