Deficiências de macronutrientes no estado nutricional da mamoneira cultivar Iris

Abstract

Resumo -Os objetivos deste trabalho foram avaliar o efeito da deficiência dos macronutrientes no crescimento e estado nutricional da mamoneira (Ricinus communis L.) e a obtenção do quadro sintomatológico das deficiên-cias de N, P, K, Ca, Mg e S. Cultivou-se Ricinus communis L. cultivar Iris em solução nutritiva, tendo como tratamentos soluções completa e deficientes em N, P, K, Ca, Mg e S. Foram determinadas a concentração indireta de clorofila, a atividade da redutase do nitrato, os teores solúveis de N (NO 3 -), P (H 2 PO 4 -) e K + e realizados testes rápidos para N, P e K. As deficiências de N, Ca, S e Mg foram as que mais restringiram a produção de massa de matéria seca, na ordem decrescente: N>Ca>S>Mg>K>P. Os maiores acúmulos de macronutrientes, no tratamento completo, foram observados nas raízes e no limbo das folhas inferiores. As concentrações críticas para N e Ca, ambas no limbo das folhas superiores e, Mg, no pecíolo das inferiores foram, respectivamente, 46,7, 13,8 e 6,5 g kg -1 . As deficiências influenciaram as leituras do clorofilômetro. A atividade da redutase do nitrato guardou relação direta com a determinação da clorofila. Os teores de N (NO 3 -), P (H 2 PO 4 -) e K + foram menores nas folhas deficientes em N, P e K, respectivamente, o mesmo acontecendo quando avaliadas pela análise de toque.Termos para indexação: Ricinus communis, clorofilômetro, nutrição, sintomas. Deficiencies of macronutrients on nutritional status of castor bean cultivar IrisAbstract -The objectives of this work were to evaluate the effect of macronutrient deficiencies on growth and on nutritional status of castor beans (Ricinus communis L.), and to obtain the symptoms of the lack of N, P, K, Ca, Mg and S. Nutrient solutions containing all macronutrients and those from which one of these elements was omitted were the treatments used. The following determinations were made: chlorophyll (indirectly), nitrate reductase activity, NO 3 --N, H 2 PO 4 --P and K + , both on soluble fractions, and by spot tests. Deficiencies of N, Ca, S and Mg were the most limiting for dry matter production, followed in decreasing order by those of K and P. The highest concentrations of macronutrients were measured in roots and lower leaf blades. Critical levels of N and Ca in the upper leaf blades and of Mg in lower petioles were respectively, 46.7, 13.8, 6.5 g kg -1. Deficiencies affected chlorophyll meter readings. Nitrate reductase activity was correlated with chlorophyll readings. Soluble contents of N, P and K in the leaves were lower in plants deficient in the respective element. The same was found when spot tests were applied on the leaf sap.

NPK fertilization on initial growth of physic nut seedlings in Quartzarenic Neossol

“…Physic nut response to N fertilization in Quartzarenic Neossol, in the plant growth stage, in this study, was not consistent with the results observed by Guimarães (2008) for the same species. In castor bean, a species of the same family as physic nut, growth was reduced when N was omitted (Lavres Júnior et al, 2005) but in another study, on the contrary, the growth was not reduced when no N was applied (Nakagawa et al, 1994). Possibly, physic nut is a species with low N demand at the initial stage of vegetative growth, even in soil with low organic matter content (Table 1).…”

CRAMBE (Crambe abyssinica) GROWTH IN SOILS UNDER DIFFERENT LEVELS OF NPK FERTILIZATION

“…In the culture of castor bean, Lavres et al (2005) reported that the total dry matter production of plants is affected by deficiencies of macronutrients, and that the most limiting element is N, but the need of each element varies depending on the plant species.…”

Nutritional Analysis of BRS Topázio Cotton Plants with Omission of Macronutrients

“…It is already known that nitrogen supply increases potassium uptake and also increases protein and soluble amino acid contents, resulting in increased production (Lavres Junior et al, 2005). In this sense, the absence of nitrogen reduces the potassium uptake and, as a consequence, the K content in plants.…”