Diferentes resposta de cutivares de soja e potássio

Soybean (Glycine max (L.) Merrill) is known to have a high ability as a potassium extractor, and different cultivars show different potassium requirements. An experiment was run to study the potassium nutrition of soybean as related to plant characteristics. Six soybean cultivars (FT-2, Bossier, IAC-11, IAC-17, IAC-18 and IAC-19) were grown in 6 kg pots filled with the topsoil of a Dark Red Latosol (sandy loam), either with and without K fertilization. The plants were harvested 70 days after emergence. Soybean response to potassium was not related to growth habit or group of maturation. There was a different response to K. The cultivars IAC-18 and FT-2 were less tolerant to K deficiency. Potassium deficiency in the leaves was not related to top dry matter production. With K fertilization soybean plants showed small root volume and higher ratio canopy/root. With high K in soil, all of the cultivars showed higher nodulation.A soja (Glycine max (L.) Merrill) apresenta grande capacidade de exploração do potássio no solo. Além disso, diferentes cultivares apresentam exigências diferentes em potássio. O objetivo deste trabalho foi estudar o comportamento de seis cultivares de soja quanto à nutrição potássica, relacionando-a aos parâmetros de crescimento. O experimento foi instalado em vasos de 6 kg de terra proveniente de um Latossolo Vermelho-Escuro de textura média, em casa de vegetação. As cultivares utilizadas foram: FT-2, Bossier, IAC- 11, IAC- 17, IAC- 18 e IAC- 19, em presença ou ausência de adubação potássica. A coleta das plantas foi realizada aos 70 dias após a emergência. A resposta da soja ao potássio aplicado não esteve relacionada ao hábito de crescimento ou ciclo das plantas. Houve diferentes respostas das cultivares ao potássio, sendo que 'IAC- 18' e 'FT-2' foram as mais prejudicadas pela falta de aplicação do nutriente. A ocorrência e a intensidade dos sintomas de deficiência de potássio não estiveram relacionadas à produção de matéria seca da parte aérea da planta. Com a aplicação de potássio ao solo, as plantas apresentaram menor peso e menor volume de raizes, e maior relação parte aérea/raiz, em peso. Plantas bem nutridas com potássio apresentaram maior peso de matéria seca de nódulos

POTASSIUM FERTILIZATION, ROOT MORPHOLOGY AND POTASSIUM ABSORPTION BY SOYBEAN

A greenhouse experiment studied the effect of potassium fertilization on soybean (Glycine max L. Merrill) root morphology and on K absorption by six soybean cultivars of different maturation groups and growth habits. The Plants were grown up to 70 days after plant emergence, in pots containing 6.0 kg of soil. In the absence of K, no significant difference in K absorption was observed among the cultivars or in root length and surface, but root mean radius was correlated to K absorption. Differences in K absorption were not associated with root characteristics in the presence of K fertilization. Physiological adjustments in K uptake, as well as K availability in the soil, were more important in soybean nutrition than were morphological adjustments in the root system. The results were not associated with plant growth habit or with maturation group