Caracterização de sintéticos de milho quanto à eficiência de uso do nitrogênio
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2018-03-22
Autores
Amaral, Camila Baptista do [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Altas doses de nitrogênio são necessárias para atingir elevadas produtividades na cultura do milho, e o uso de genótipos eficientes no uso de nitrogênio permitiria atingir tais produtividades utilizando menor quantidade de fertilizantes nitrogenados. O objetivo do trabalho foi caracterizar sintéticos de milho quanto à eficiência de uso de nitrogênio e estudar as correlações entre os componentes da eficiência. Para caracterizar os sintéticos a campo, foram conduzidos experimentos na safra 2015/2016 e 2016/2017. Doze sintéticos e duas testemunhas comerciais (AL Avaré e Ipanema) foram cultivadas sob alta e baixa disponibilidade de nitrogênio em cada uma das safras, totalizando quatro experimentos. Sob baixa disponibilidade de nitrogênio, apenas 24 kg ha-1 do elemento foram aplicados na semeadura, enquanto que sob alta disponibilidade, a adubação nitrogenada foi constituída de 24 kg ha-1 na semeadura e 120 kg ha-1 em cobertura no estádio V4-5. Os experimentos foram conduzidos no delineamento de blocos ao acaso, e foram avaliados o índice do conteúdo de clorofila, acamamento, prolificidade e produtividade de grãos. A disponibilidade de nitrogênio alterou o índice do conteúdo de clorofila dos sintéticos, sendo que maiores valores foram observados sob alta disponibilidade de nitrogênio. Todas os sintéticos foram considerados adequados para cultivo sob baixa disponibilidade de nitrogênio, pois não houve diferença entre alta e baixa disponibilidade para os caracteres acamamento, prolificidade e produtividade de grãos. Considerando todos os caracteres estudados, dois sintéticos foram identificados como superiores, por apresentarem altos valores de índice de conteúdo de clorofila, resistência ao acamamento, prolificidade e produtividade de grãos, com desempenho superior às testemunhas. A fim de estudar os caracteres relacionados com a eficiência de uso de nitrogênio, dois sintéticos e uma testemunha, AL Avaré, foram cultivados em vasos, sob níveis contrastantes de disponibilidade de nitrogênio. Sob baixa disponibilidade, foram aplicados 100 mg dm-3 de nitrogênio em cada vaso na semeadura, e sob alta disponibilidade, foram aplicados 100 mg dm-3 por vaso na semeadura, 150 mg dm-3 em V3 e 150 mg dm-3 em V5. O experimento foi conduzido no delineamento de blocos ao acaso, em esquema fatorial 3x2. Foram avaliados o índice do conteúdo de clorofila, massa seca da parte aérea, massa seca da raiz, eficiência de absorção, eficiência de utilização e eficiência de uso de nitrogênio. O índice de conteúdo de clorofila diferiu entre os níveis contrastantes de nitrogênio, mas não entre os sintéticos. A massa seca da parte aérea foi diminuída pela baixa disponibilidade de nitrogênio, enquanto a resposta dos sintéticos para massa seca da raiz foi variável em função da disponibilidade de nitrogênio. Houve correlação forte e positiva entre eficiência de absorção e eficiência de uso de nitrogênio, sendo que a eficiência de absorção foi correlacionada com a massa seca das raízes.
High doses of nitrogen are necessary to reach high yields in maize crop, and the use of genotypes efficient in the use of nitrogen would allow to reach such productivities using less amount of nitrogen fertilizers. The objective of this work was to characterize maize synthetics as to nitrogen use efficiency and to study the correlations between the efficiency components. To characterize the synthetic in a field level, experiments were conducted in 2015/2016 and 2016/2017 seasons. Twelve synthetics and two commercial control (AL Avaré and Ipanema) were cultivated under high and low nitrogen availability in each of the seasons, totalizing four experiments. Under low nitrogen availability, only 24 kg ha-1 of the element were applied at sowing, while under high availability, nitrogen fertilization consisted of 24 kg ha-1 at sowing and 120 kg ha-1 topdressed at the V4-5. The experiments were conducted in a randomized complete block design, and the chlorophyll content index, lodging, prolificacy and grain yield were evaluated. The nitrogen availability altered the chlorophyll content index of the synthetic, and higher values were observed under high nitrogen availability. All the synthetics were considered suitable for cultivation under low nitrogen availability, since there was no difference between high and low availability for lodging, prolificacy and grain yield. Considering all the traits studied, two synthetics were identified as superior, because they presented high values of chlorophyll content index, lodging resistance, prolificacy and grain yield, with superior performance to the control. In order to study the traits related to nitrogen use efficiency, two synthetics and one control, AL Avaré, were grown in pots, under contrasting levels of nitrogen availability. Under low availability, 100 mg dm-3 of nitrogen was applied to each pot at sowing, and under high availability, 100 mg dm-3 per pot was applied at sowing, 150 mg dm-3 at V3 and 150 mg dm-3 at V5. The experiment was conducted in a randomized complete block design, in a 3x2 factorial scheme. The chlorophyll content index, shoot dry mass, root dry mass, uptake efficiency, utilization efficiency and nitrogen use efficiency were evaluated. The chlorophyll content index differed between the contrasting levels of nitrogen, but not among the synthetics. The shoot dry mass was diminished by the low nitrogen availability, while the response of the synthetics to root dry mass was variable as a function of the nitrogen availability. There was a strong and positive correlation between uptake efficiency and nitrogen use efficiency, and the uptake efficiency was correlated with the root dry mass.
High doses of nitrogen are necessary to reach high yields in maize crop, and the use of genotypes efficient in the use of nitrogen would allow to reach such productivities using less amount of nitrogen fertilizers. The objective of this work was to characterize maize synthetics as to nitrogen use efficiency and to study the correlations between the efficiency components. To characterize the synthetic in a field level, experiments were conducted in 2015/2016 and 2016/2017 seasons. Twelve synthetics and two commercial control (AL Avaré and Ipanema) were cultivated under high and low nitrogen availability in each of the seasons, totalizing four experiments. Under low nitrogen availability, only 24 kg ha-1 of the element were applied at sowing, while under high availability, nitrogen fertilization consisted of 24 kg ha-1 at sowing and 120 kg ha-1 topdressed at the V4-5. The experiments were conducted in a randomized complete block design, and the chlorophyll content index, lodging, prolificacy and grain yield were evaluated. The nitrogen availability altered the chlorophyll content index of the synthetic, and higher values were observed under high nitrogen availability. All the synthetics were considered suitable for cultivation under low nitrogen availability, since there was no difference between high and low availability for lodging, prolificacy and grain yield. Considering all the traits studied, two synthetics were identified as superior, because they presented high values of chlorophyll content index, lodging resistance, prolificacy and grain yield, with superior performance to the control. In order to study the traits related to nitrogen use efficiency, two synthetics and one control, AL Avaré, were grown in pots, under contrasting levels of nitrogen availability. Under low availability, 100 mg dm-3 of nitrogen was applied to each pot at sowing, and under high availability, 100 mg dm-3 per pot was applied at sowing, 150 mg dm-3 at V3 and 150 mg dm-3 at V5. The experiment was conducted in a randomized complete block design, in a 3x2 factorial scheme. The chlorophyll content index, shoot dry mass, root dry mass, uptake efficiency, utilization efficiency and nitrogen use efficiency were evaluated. The chlorophyll content index differed between the contrasting levels of nitrogen, but not among the synthetics. The shoot dry mass was diminished by the low nitrogen availability, while the response of the synthetics to root dry mass was variable as a function of the nitrogen availability. There was a strong and positive correlation between uptake efficiency and nitrogen use efficiency, and the uptake efficiency was correlated with the root dry mass.
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Palavras-chave
Eficiência de absorção, Eficiência de uso, Estresse abiótico, Produtividade, Zea mays, use efficiency, abiotic stress, grain yield, uptake efficiency