Eurípedes Malavolta

Alterações químicas em solos ácidos após a aplicação de resíduos vegetais

Understanding the chemistry behavior in acid soils during the decomposition of plant residues is very important for the management of these soils. The effects of incubation (0, 15, 30, 60 and 90 days) of finely ground residues of oil seed radish (Raphanus sativus), soybean (Glycine max) and wheat (Triticum aestivum) (at 2 and 4%) with samples of Bw horizon of three Oxisols of the state of Parana, Brazil, on the soil pH, dissolved organic carbon (DOC) and soluble and exchangeable Al, Ca, Mg and K were verified during 1995-1996. DOC and total and soluble Ca, Mg and K were determined in the plant residues. Immediately after application of plant residues (zero time), there were increases in pH, in exchangeable and soluble Ca, Mg, and K, in soluble Al and DOC and a decrease in exchangeable Al. The intensity of these changes was associated with the DOC and with the soluble Ca, Mg and K in the residues, in the following order: oil seed radish > soybean > wheat. During incubation, the DOC of the soil solution rapidly decreased. DOC decrease with the incubation time did not affect K, but drastically reduced Al, Ca and Mg in the soil solution, showing the importance of DOC in the maintenance of cations in solution through the formation mechanism of organic complexes. The chemical speciation estimated that more than 90% of the total Al in solution was in the organic form. The organic and inorganic compositions of the water soluble fraction of plant residues were the main factor responsible for the chemical changes observed in the acid soil samples.

Effect of nickel on two common bean cultivars

Abstract Two common bean (Phaseolus vulgaris L.) cultivars, Carioca and IAPAR‐14, were grown in a nutrient solution in the presence of 0,1,2, and 4 mg/L of nickel (Ni). Both cultivars developed symptoms of toxicity in the roots and tops., but especially in the leaves. Dry matter was reduced by the higher Ni levels. The IAPAR‐14 cultivar, however, was more tolerant than the Carioca cultivar to Ni. Yield decreased as Ni levels in the solutions were increased. There was no seed production at the 4 mg/L Ni concentration for either of the two cultivars. A 50% reduction in leaf chlorophyll was observed when 4 mg/L Ni was supplied. Mineral analysis of several plant parts showed a build up of Ni concentration in the roots which was accompanied by higher iron (Fe) concentrations. Increasing Ni supply resulted in no significant changes in the concentrations of calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) in the tissue. The levels of nitrogen (N), phosphorus (P), potasium (K), copper (Cu), and Ni, how...

Dinâmica de íons em solo ácido lixiviado com extratos de resíduos de adubos verdes e soluções puras de ácidos orgânicos

The influence of green manure residues addition in the dynamic of ions in acid soils is not well known. In this study, ion mobility in a sample of the Bw horizon of an Dark-Red Latosol (Oxisol), leached with citric and succinic acid pure solutions and with aqueous residue extracts of black oats (Avena strigosa) and oil seed radish (Raphanus sativus) were evaluated in soil columns (5, 10, 20, and 40 cm long by 4 cm diameter). After the solutions and extracts passed through the soil columns, the following parameters were determined: solubles contents of Cas, Mgs, Ks, Alst (total), Also (organic), Alsm (monomeric) and dissolved organic carbon. In soil, the parameters evaluated were the exchangeable contents of Caex, Mgex, Kex, and Alex and pH (CaCl2). Citric and succinic acids increased Alst and Cas contents, respectively, resulting in decreasing exchangeable fractions of these elements in soil. Black oats extract was more effective to extract Caex and oil seed radish to extract Alex. The decrease in Caex and Alex was followed by an increase in Kex. Organic complexes formed with low molecular organic ligands and Cas and Alex were suggested to play a role in the mobility of ions in subsoils of acid soils after the addition of both crop residues extracts and pure organic acid solutions.

Dinâmica da matéria orgânica e da biomassa microbiana em solo submetido a diferentes sistemas de manejo na Amazônia Ocidental

The objective of this work was to evaluate the alterations of the microbial biomass activity as an indicator of C and N dynamics in a soil submitted to the succession of plant cover and management in the Western Amazon. The work was carried out in two chronosequences: CA - a succession from primary forest to a three years old cupuacu (Theobroma grandiflorum) plot - and CB - a succession from primary forest to an eight years old Brachiaria humidicola pasture and a three years old cupuacu plot. The succession primary forest-pasture-cupuacu affects negatively the stock of the soil carbon, with significant decrease of organic matter and C of the soil microbial biomass. The primary forest presents lower metabolic quotient and higher C/N ratio of the biomass, which results in less carbon loss. The N of the microbial biomass found in the 0-10 cm layer irrespective of the management adopted, increases significantly in the cupuacu plot and the total N decreases. Ammonium concentration decreases according to soil depth, but this does not occur with nitrate.

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.

Studies on mineral nutrition of the coffee plant (Coffea arabica L. cv. Catuaí Vermelho): LXIV. Remobilization and re-utilization of nitrogen and potassium by normal and deficient plants

Remobilization and re-utilization of 15N and 85Rb labelled nitrogen and potassium reserves for new growth and fruit formation was studied under greenhouse conditions using both normal and deficient young coffee plants. It was found that K reserves are used in higher proportion than is stored N by fruits and other organs. The export of N by organs of residence in the normal plants obeyed the following proportions of the total: leaves 47%-58%, branches and flower buds 21%-27%, roots 21%-32%. The corresponding figures in the case of deficient plants were: leaves 49%-65%, branches and flower buds 21%-27%, roots 14%-25%. Re-utilization of K took place in the following proportions in the normal plants: leaves 54%-64%, branches and flower buds 20%-21%, roots 30%-41%. In K deficient plants the figures were: leaves 62%-79%, branches and flower buds 1.2%-4.4%, roots 20%-33%. In tissues formed after the initiation of flowering buds, the demand for N is met by reserves as follows: normal plants: fruits 20.6%-24.8%, leaves 15.6%-19.4%, twigs 19%-20.5%; deficient plants: fruits 43.5%-48.5%, leaves 48.1%-51.9%, twigs 46%-53%. The K needs for new tissues are met in the order: normal plants: fruits 40%-45.8%, leaves 27%-37.6%, twigs 26%-33.1%; deficient plants: fruits 65.7%-81.5%, leaves 52.6%-68.4%, twigs 62%-86.1%. Fruits represent the main sink for both N and K. Reutilization of both elements is higher in the case of deficient plants.

Eficiência de fontes e doses de fósforo na alfafa e centrosema cultivadas em Latossolo Amarelo (1)

-1 ), com tres repeticoes, sendo realizados seis cortes. A eficiencia das fontes e doses de P foi determinada por tres metodos: Indice de Eficiencia Agronomica, Equivalente Superfosfato Triplo e Indice de Eficiencia; o P recuperado foi avaliado por Mehlich 1, Mehlich 3 e resina. Os melhores indices de Eficiencia Agronomica e Equivalente Superfosfato Triplo foram obtidos com o termofosfato Yoorin. O Indice de Eficiencia foi maior na centrosema do que na alfafa. Com a sequencia de cortes, a producao de materia seca obtida com os fosfatos naturais reativos tende a equiparar-se a das fontes mais soluveis. O termofosfato Yoorin eleva o pH do solo, enquanto o superfosfato triplo o diminui; os fosfatos naturais apresentam reacao neutra. Termos para indexacao: Centrosema pubescens , Medicago sativa, adubo fosfatado, extrator, acidificacao. Efficiency of phosphorus sources and rates for alfalfa and centrosema cultivated in an Yellow Latosol (Oxisol)

Deficiências de macronutrientes no estado nutricional da mamoneira cultivar Iris

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, H2PO4 - -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.

Efeitos do manganês sobre a soja cultivada em solo de Cerrado do Triângulo Mineiro

Manganese deficiency in soybean [Glycine max (L.) Merrill) and in other crops could be due to its low levels in the soil, or to its unavailability induced by liming. The objective of this research was to verify the soybean mineral composition in relation to Mn availability. An experiment was carried out in a greenhouse, using soil from Patrocinio, MG, Brazil, where the cultivated coffee shows symptoms of Mn deficiency. Mn was applied at the rates of zero, 10, 50 and 100 mg kg with an additional treatment of 0.6% of foliar applied Mn and two rates of lime, namely: zero and 2.7 t ha. Mn concentration in the plant tissue was increased with the rate of lime application; liming, however, caused a Mn reduction. It must be pointed out that the lowest Mn level in the leaves was 84 mg kg, at the zero rate of Mn with lime. Mn ratio caused an increase both in dry matter and grain yield either in the presence and absence of lime. Liming did not induce any symptom of Mn deficiency in the leaves. Leaf applied Mn was efficient to raise and maintain soybean yield.

Aluminum tolerance in sorghum and bean ‐ methods and results

Abstract Average pH of Brazilian soils is circa 5.5 and in case of the “cerrado” (around 2.0 million square kilometers) is even lower. Low Ca, Mg and K in the exchange complex is accompanied by high Al saturation. Lime use has not kept up with the increase in fertilizer consumption which is a contributing factor for further decrease in pH. Hence the interest of screening and breeding varieties of food crops with some degrees of tolerance to Al toxicity. This paper summarizes results obtained in experiments designed to differentiate among 30 cultivars each of grain sorghum and beans those less sensitive to high levels of Al in the medium, as well as to establish rapid methods for screening, and to determine relationship between aluminum effect and mineral nutrition. Care was taken to separate Al from H ion effects. Preliminary trials showed that dry matter production by seedlings grown for short periods gave better indication of Al tolerance than other parameters. Very close correlations were found to exis...