Reges Heinrichs

Evaluation of Nutritional Status of the Cotton Plant with Respect to Nitrogen

Abstract Cotton plants, Gossypium hirsutum L. cv. Antares, were grown in nutrient solution, under three levels of nitrogen (N) supply, in order to assess their effects on growth and yield, and to evaluate the N status by the following methods: visual symptoms, changes in the leaf ultrastructure, direct and indirect determinations of leaf chlorophyll (SPAD readings); NO3-N in the petiole both, by spot test in vivo and by quantitative determination; total N in the leaf blade and nitrate reductase activity (NO3 R) in the same; total N in the seeds. Low N level in the solution drastically reduced vegetative growth components, number of bolls and seed cotton and fiber yields. Nitrogen deficiency caused yellowing of the leaves beginning in the older ones. The main changes in the ultrastructure of the N deficient leaves were the disruption of the chloroplast membrane and the accumulation of starch granules and lipid globules. The semiquantitative assessment of nitrate in the petiole was unable to differentiate between the upper levels of nitrogen supply, this being also the case for seed N. Nitrogen status was well correlated both with the quantitative determination of NO3-N and with the NO3 R activity. Both direct and indirect determinations of leaf chlorophyll (SPAD readings) were able to reflect the N status, showing significant correlation with yield.

Influência do magnésio na absorção de manganês e zinco por raízes destacadas de soja

-1 ) x cinco doses de Zn ou Mn (0,5, 1,0, 2,0, 5,0 e 10,0 µmol L -1 ), com tres repeticoes. Com pipetador, foi colocado 14,8 MBq de radiozinco ou de radiomanganes. Apos uma hora de exposicao, as raizes foram lavadas e secadas em estufa; em seguida foram pesadas e determinou-se a radioatividade. Os valores foram convertidos em micromoles por grama de materia seca. Foram estimadas as variaveis Km e Vmax pela equacao de Lineweaver & Burk. As cultivares apresentaram comportamentos distintos na absorcao de Mg, Mn e Zn; a inibicao do Mg sobre o Zn e o Mn na soja e do tipo nao competitiva, e as variaveis Km e Vmax comportaram-se de modo independente no processo de absorcao. Termos para indexacao: Glycine max, nutriente, inibicao, carencia mineral. Magnesium influence on manganese and zinc uptake by excised roots of soybean

Brachiaria sp YIELD AND NUTRIENT CONTENTS AFTER NITROGEN AND SULPHUR FERTILIZATION

Among the production factors, adequate fertilization is an important tool to raise the productivity of pastoral systems and consequently increase the share of Brazil in the supply chain of primary agricultural products at the global level. The objective of this study was to evaluate the interaction of nitrogen and sulfur fertilization in BRACHIARIA DECUMBENS: Stapf. The experiment in pots with Dystrophic Oxisol was evaluated in a completely randomized design with four replications in a 5 x 3 factorial arrangement, involving five N doses (0, 100, 200, 400, and 800 mg dm-3) in the form of ammonium nitrate and three S doses (0, 20 and 80 mg dm-3) in the form of calcium sulfate, with a total of 15 treatments. In the treatments with low S dose, calcium was provided as calcium chloride, to ensure a homogeneous Ca supply in all treatments. The results showed that the tiller production and dry weight of green leaves and of stems + sheaths and total dry weight were favored by the combination of N and S fertilizer, while the proportion of dry leaves was reduced. Nitrogen fertilization raised the N contents in green leaves and stems + sheaths and reduced K contents in fresh and dry leaves. The response to S rates in the N content of green leaves was quadratic.

RETENÇÃO DE ÁGUA EM UM LATOSSOLO EM RECUPERAÇÃO COM ADUBOS VERDES

RESUMO A degradacao dos solos e caracterizada pela mudanca na qualidade da estrutura, provocando diminuicao no tamanho dos poros, especialmente dos macroporos, o que leva a reducao na area da secao transversal para o fluxo de agua. Com isso, o objetivo deste trabalho foi avaliar a retencao de agua de um Latossolo em recuperacao com adubos verdes. O delineamento experimental foi inteiramente casualizados, com 9 tratamentos e 4 repeticoes. Os tratamentos foram: Testemunha (solo mobilizado) ; Mucuna-preta ( Stizolobiumaterrimum Piper & Tracy); Guandu ( Cajanuscajan L. Millsp), ate 1994, apos substituido por Feijao-de-porco ( Canavalia ensiformes L) ; Calcario+Mucuna-preta ; Calcario+Guandu ate 1994, apos substituido por Feijao-de-porco; Calcario+Gesso+Mucuna-preta ; Calcario+Gesso+Guandu, ate 1994, apos substituido por Feijao-de-porco, duas Testemunhas T1 - Solo exposto (sem tecnica de recuperacao) e T2 - Vegetacao nativa de Cerrado. Todos os tratamentos de recuperacao apos 1999 foram conduzidos com Brachiaria decumbens. Foi realizada coleta de solo (amostras indeformadas), nas camadas de 0,00-0,10; 0,10-0,20 e 0,20-0,40m para a determinacao da retencao de agua no solo, no ano de 2010. Os tratamentos de recuperacao nao influenciaram a retencao de agua no solo. A vegetacao nativa do cerrado obteve menor valor, devido a melhor distribuicao de tamanho de poros. Observou que quanto maior a retencao de agua, maior a microporosidade do solo.Conclui-se que o solo ainda nao esta recuperado avaliando a retencao de agua no solo.Na camada superficial do solo, a retencao de agua e menor do que nas camadas mais profundas. PALAVRAS-CHAVE: porosidade do solo. area degradada. Materia orgânica.