The nitrogen sufficiency index underlying estimates of nitrogen fertilization requirements of common bean
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Data
2012-02-01
Autores
Maia, Suelen Cristina Mendonça [UNESP]
Soratto, Rogério Peres [UNESP]
Nastaro, Beatriz
Freitas, Lucas Barbosa de [UNESP]
Título da Revista
ISSN da Revista
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Editor
Sociedade Brasileira de Ciência do Solo
Resumo
As leituras indiretas de clorofila, obtidas com clorofilômetro portátil, podem indicar a época de maior demanda de N pelas plantas e se há ou não necessidade de sua aplicação em cobertura. Nesse sentido, a definição da melhor época para aplicação de N na cultura do feijão é fundamental para aumentar a eficiência de uso do N e a produtividade de grãos e reduzir custos com fertilizantes. Objetivou-se avaliar a eficiência do índice de suficiência de nitrogênio (ISN) de 90 e 95 %, calculado com base no índice relativo de clorofila (IRC) nas folhas, das plantas da área de referência, como indicador do momento de aplicação da adubação nitrogenada de cobertura no feijoeiro cultivar Pérola. O experimento foi conduzido durante as safras das águas e da seca no ano agrícola de 2009/10, em um Nitossolo Vermelho distroférrico, em Botucatu (SP). O delineamento experimental foi em blocos casualizados com cinco tratamentos, constituídos por manejos de N - M1: 200 kg ha-1 (40 kg na semeadura + 80 kg 15 dias após a emergência (DAE) + 80 kg 30 DAE); M2: 100 kg ha-1 (20 kg na semeadura + 40 kg 15 DAE + 40 kg 30 DAE); M3: 20 kg ha-1 na semeadura e 30 kg ha-1 quando o ISN < 95 %; M4: 20 kg ha-1 na semeadura e 30 kg ha-1 quando o ISN<90 %; e M5: testemunha sem N - e quatro repetições. Foram avaliados o IRC, a massa de matéria seca da parte aérea, o teor de N total nas folhas, os componentes de produção, a produtividade de grãos, a produtividade relativa e a eficiência de utilização do N aplicado. O IRC correlacionou-se com o teor de N na folha do feijoeiro. O monitoramento do IRC com o clorofilômetro permitiu definir quando se deve aplicar o N em cobertura no feijoeiro, melhorando a eficiência de utilização e evitando a aplicação desnecessária desse nutriente em cobertura na cultura do feijoeiro. O ISN de 90 % foi mais eficiente para definir quando aplicar N em cobertura no feijoeiro, por proporcionar maior eficiência de utilização.
Chlorophyll determination with a portable chlorophyll meter can indicate the period of highest N demand of plants and whether sidedressing is required or not. In this sense, defining the optimal timing of N application to common bean is fundamental to increase N use efficiency, increase yields and reduce the cost of fertilization. The objectives of this study were to evaluate the efficiency of N sufficiency index (NSI) calculated based on the relative chlorophyll index (RCI) in leaves, measured with a portable chlorophyll meter, as an indicator of time of N sidedressing fertilization and to verify which NSI (90 and 95 %) value is the most appropriate to indicate the moment of N fertilization of common bean cultivar Perola. The experiment was carried out in the rainy and dry growing seasons of the agricultural year 2009/10 on a dystroferric Red Nitosol, in Botucatu, São Paulo State, Brazil. The experiment was arranged in a randomized complete block design with five treatments, consisting of N managements (M1: 200 kg ha-1 N (40 kg at sowing + 80 kg 15 days after emergence (DAE) + 80 kg 30 DAE); M2: 100 kg ha-1 N (20 kg at sowing + 40 kg 15 DAE + 40 kg 30 DAE); M3: 20 kg ha-1 N at sowing + 30 kg ha-1 when chlorophyll meter readings indicated NSI < 95 %; M4: 20 kg ha-1 N at sowing + 30 kg ha-1 N when chlorophyll meter readings indicated NSI < 90 % and, M5: control (without N application)) and four replications. The variables RCI, aboveground dry matter, total leaf N concentration, production components, grain yield, relative yield, and N use efficiency were evaluated. The RCI correlated with leaf N concentrations. By monitoring the RCI with the chlorophyll meter, the period of N sidedressing of common bean could be defined, improving N use efficiency and avoiding unnecessary N supply to common bean. The NSI 90 % of the reference area was more efficient to define the moment of N sidedressing of common bean, to increase N use efficiency.
Chlorophyll determination with a portable chlorophyll meter can indicate the period of highest N demand of plants and whether sidedressing is required or not. In this sense, defining the optimal timing of N application to common bean is fundamental to increase N use efficiency, increase yields and reduce the cost of fertilization. The objectives of this study were to evaluate the efficiency of N sufficiency index (NSI) calculated based on the relative chlorophyll index (RCI) in leaves, measured with a portable chlorophyll meter, as an indicator of time of N sidedressing fertilization and to verify which NSI (90 and 95 %) value is the most appropriate to indicate the moment of N fertilization of common bean cultivar Perola. The experiment was carried out in the rainy and dry growing seasons of the agricultural year 2009/10 on a dystroferric Red Nitosol, in Botucatu, São Paulo State, Brazil. The experiment was arranged in a randomized complete block design with five treatments, consisting of N managements (M1: 200 kg ha-1 N (40 kg at sowing + 80 kg 15 days after emergence (DAE) + 80 kg 30 DAE); M2: 100 kg ha-1 N (20 kg at sowing + 40 kg 15 DAE + 40 kg 30 DAE); M3: 20 kg ha-1 N at sowing + 30 kg ha-1 when chlorophyll meter readings indicated NSI < 95 %; M4: 20 kg ha-1 N at sowing + 30 kg ha-1 N when chlorophyll meter readings indicated NSI < 90 % and, M5: control (without N application)) and four replications. The variables RCI, aboveground dry matter, total leaf N concentration, production components, grain yield, relative yield, and N use efficiency were evaluated. The RCI correlated with leaf N concentrations. By monitoring the RCI with the chlorophyll meter, the period of N sidedressing of common bean could be defined, improving N use efficiency and avoiding unnecessary N supply to common bean. The NSI 90 % of the reference area was more efficient to define the moment of N sidedressing of common bean, to increase N use efficiency.
Descrição
Palavras-chave
Phaseolus vulgaris, clorofila, índice relativo de clorofila, clorofilômetro, Phaseolus vulgaris, chlorophyll, relative chlorophyll index, chlorophyll meter
Como citar
Revista Brasileira de Ciência do Solo. Sociedade Brasileira de Ciência do Solo, v. 36, n. 1, p. 183-192, 2012.