Non destructive estimation of foliar nitrogen in cacao tree using chlorophyll meter/Estimativa nao destrutiva do teor foliar de nitrogenio em cacaueiro utilizando clorofilometro

• Published in: Revista Brasileira de fruticultura Vol. 34; no. 3; p. 669
• Main Authors: Dantas, Paulo Alfredo De Santana, Junior, Jose Olimpio De Souza Junior, Gomes, Fabio Pinto, Ribeiro, Daniel Ornelas
• Format: Journal Article
• Language: Spanish
• Published: Sociedade Brasileira de Fruticultura 01.09.2012
• ISSN: 0100-2945

The replacement of the traditional method for evaluating the nitrogen (N) in the plant by the use of portable chlorophyll meter SPAD is promising because it is a portable device that provides a nondestructive, instant and low cost index. This study aimed to determine the ability of this device in estimating leaf N content of cocoa. The area covered by this study involves the wet and humid climate zones of the sub humid cocoa region of Bahia. Were selected ten farms, in each area, with crops in agroforestry system and that the area had renewed by grafting of basal shoot with clones tolerant to witches' broom. In each farm, four plants over the age of four years were selected in different topographic and soil conditions. It was collected eight healthy leaves per plant and in each, was made six SPAD readings of the index. Furthermore, were determined the N content, N content, leaf area (LA) and specific leaf mass (SLM). The SPAD index was significantly positively correlated with leaf N content (r = 0.74), with AF (r = 0.62) and negatively with the MFE (r =-0.57). There was no correlation between N content and SPAD index. There was no correlation between N content and SPAD index. The simple linear regression model to predict the N content from SPAD index, without distinction of environments was more appropriate. Index terms: ecophysiology, Theobroma cacao, nutritional diagnosis. A substituicao do metodo tradicional de avaliacao do teor de nitrogenio (N) na planta pelo uso do medidor portatil de clorofilas do tipo SPAD e promissora por se tratar de um aparelho portatil que estabelece um indice de modo nao destrutivo, instantaneo e com menor custo. Objetivou-se determinar a capacidade deste aparelho em estimar o teor foliar de N do cacaueiro. A area de abrangencia deste estudo envolve as zonas climaticas umida e umida a subumida da regiao cacaueira da Bahia. Foram selecionadas dez propriedades rurais, em cada zona, com lavoura em sistema agrossilvicultural, que tiveram a area renovada por enxertia de broto basal com clones tolerantes a vassoura-de-bruxa. Em cada propriedade, quatro plantas com idade superior a quatro anos foram selecionadas em condicoes edaficas e topograficas distintas. Foram coletadas oito folhas sadias por planta e, em cada uma delas, foram feitas seis leituras do indice SPAD. Alem disso, determinaram-se o teor e o conteudo de N na folha, a area foliar (AF) e a massa foliar especifica (MFE). O indice SPAD correlacionou se, significativa e positivamente com o teor foliar de N (r = 0,74), com a AF (r = 0,62) e negativamente com a MFE (r = -0,57). Nao houve correlacao entre o conteudo de N e o indice SPAD. O modelo de regressao linear simples para a predicao do teor de N, a partir do indice SPAD, sem a distincao dos ambientes, foi o mais apropriado. Termos para indexacao: ecofisiologia, Theobroma cacao, diagnostico nutricional.