Estado nutricional da cultura de cana-de-açúcar (cana-planta) em experimentos com 15N

Abstract

RESUMOEstudos com isótopos estáveis são cada vez mais comuns pela qualidade e confiabilidade dos resultados obtidos e por não apresentarem risco ao homem e ao ambiente. No entanto, é necessário o uso de microparcelas para diminuir o custo do projeto. Por suas áreas serem muito reduzidas em relação à parcela onde está inserida, o objetivo deste trabalho foi comparar o estado nutricional de plantas das microparcelas com as do restante das parcelas experimentais, na fase de máximo desenvolvimento da cultura da cana-de-açúcar, em experimentos com doses de N. Foram instalados três experimentos, no Estado de São Paulo, com três doses de N e uma testemunha, com quatro repetições, em delineamento em blocos completos casualizados. Nas parcelas, de 48 linhas de 15 m cada, foram instaladas microparcelas de 3 m 2 com fertilizante-15 N. Na época de máximo desenvolvimento da cultura foram coletadas folhas-diagnóstico para a avaliação de seu estado nutricional em todas as parcelas e microparcelas. Nessas folhas foram determinados os teores de macronutrientes, e os resultados foram submetidos à análise de variância. Foram comparados, em cada área experimental e de forma conjunta, os resultados das parcelas com os das microparcelas quanto aos teores foliares dos nutrientes e, quando significativo o efeito das doses de N na variação desses, foram feitas regressões. Não houve diferença entre os teores de N, P, Ca, Mg e S das folhas-diagnóstico entre as parcelas e as microparcelas, as quais foram

Nutritional diagnosis of sugarcane varieties in a Yellow Oxisol during three agricultural seasons

“…The average levels in the three cycles were below the levels indicated by Malavola et al (1997), but within the range recommended by Orlando Filho (1983). The leaf S content during plant-cane was similar to that observed by Faroni et al (2009), but, during regrowth, the levels increased. A "dilution effect" may have occurred on the plant-cane.…”

“…Calcium levels in the +3 leaf, during the plant-cane cycle, are of the same order of magnitude as mentioned by Faroni et al (2009), Oliveira et al (2011b and Omollo et al, (2016). During the first regrowth, an average content of 4.72 g kg -1 was observed.…”

Nutrient extraction by mombaga grass submitted to sources and doses of nitrogen

“…Cantarela (2007) reported the synergism existing between N and K and between N and Ca. Faroni et al (2009) observed that increased nitrogen fertilisation resulted in increased K absorption in sugar cane plants, and the author attributed this behaviour to the synergism between the nutrients. When calcium nitrate was used, Ca extraction by the plants occurred in a quadratic manner, with greater extraction values reported with calcium nitrate than with other sources of N. These results can be explained by the indirect supply of Ca to the soil through the nitrogen fertiliser, which allows a greater absorption of this nutrient by plants.…”

Evaluating Nitrogen Behavior in Sugarcane after Fertilization Using Leaf and Sap Extract Analyzes

“…For many crops, leaf analysis is an effective tool for diagnosing plant nutritional status [28]. However, leaf analysis in sugarcane typically has low response to changes in sugarcane nutrition, and differences in stalk yield are often observed without detecting differences during leaf analysis [7] [8]. This discrepancy can normally be explained by dilution effects [29] and the difficulties involved in determination of diagnostic leaf and the best time to sample the leaves.…”

“…According to [6], the highest uptake of N occurs during the initial development stages, typically within 90 days of fertilization, before full development of the canopy. Thus, leaf analysis performed after canopy closure may not represent the positive responses of N fertilization in the crop yield [7] [8].…”