Em um latossolo, com teor de P disponível entre baixo e médio foi instalado um ensaio destinado a comparar a eficiência de um fosfato natural parcialmente acidulado (FAPS) com a do super simples (SS) e a do fosfato de Araxá (FA) original, na cultura da cana-de-açúcar (cana-planta). Os dados obtidos mostraram que: (1) o FAPS deu uma produção que não diferiu estatisticamente da obtida com o SS, sendo superior ao FA como fonte de P2O5; (2) os dados de diagnose foliar sugerem que o FAPS e o SS funcionam como fonte de P e de S; (3) o teor de açúcares redutores no caldo aumentou em consequência da adubação fosfatada; (4) o FAPS, na dose mais alta, elevou o teor de sacarose do caldo.

The relative efficiency of a partially acidulated and granulated rock phosphate, FAPS, containing 26% total P2O5, 10% citric acid soluble P2O5, 13% ammonium citrate soluble P2O5, 27% total CaO and 7% total S, was compared with that of both simple superphosphate (SS) and ground rock phosphate (FA). The experiment with the sugar cane variety NA 56-79 was set in a red yellow latosol, pH 5.1-5.5, low in P (4 ppm), and with and average available sulphur content (5 ppm as sul fate). The main conclusions were as follows: a) FAPS gave the same yield results provided by SS when used at the same rates based on total P2O5 content; b) sucrose content in the juice was increased by the highest level (16a kg P2O5 of application of FAPS; c) leaf analyses data suggest that FAPS has incre ased yield by supplying both P2O5 and S to the sugar-cane crop.

Em solos pouco ácidos, pobres em P disponível, dois dos quais anteriormente com vegetação de cerrado, foram conduzidos ensaios destinados a comparar a eficiência de um fosfato natural parcialmente acidulado com ácido sulfúrico (FAPS) com a do super simples (SS) e a do fosfato de Araxá original. Usaram-se as culturas de arroz de sequeiro, milho e soja. Verificou-se que: (1) o FAPS deu produções que não diferiram estatísticamente das obtidas com o SS sendo maiores que as conseguidas com o FA; (2) os resultados das análises de solos e da diagnose foliar indicam que o FAPS funcionou como fonte de P, Ca e S.

In slightly acidic soils the effect of two rates of PARP (60 and 120 kg P2O5 per hectare) was compared to that of single superphosphate and of the original ground Araxá rock phosphate (ARP), both supplied to give 90 kg P2O5/ha. Testcrops were: upland rice, corn and soybeans. Main conclusions, based on yield data, and soil and leaf analyses were the following: (1) there was no statistical diferrence between yields obtained with PARP and SS which, however, were ussuallu higher than those provided for by ARP; (2) results from chemical analyses show that the PARP, as well as the SS, were a source of P, Ca and S to the three crops; (3) under the experimental conditions, there fore, the effect of the PARP was close to that of the SS rather than to the effect due to the ARP.

Sorgo sacarino, cv Brandes, foi cultivado em solução nutritiva deficiente em macro e micronutrientes e com excesso de alumínio, cloro e manganês. Foram obtidos sintomas das deficiências e excessos provocados no meio e o material foi analisado. Obteve-se uma estimativa das exigências nutricionais. Análises tecnológicas do colmo, mostraram os efeitos das deficiências de nitrogênio, fósforo e potássio sobre as mesmas.

Sweet sorghum cv Brandes was grown in nutrient solution under stress of macro and micronutrients, as well as in the presence of toxic levels of Al, Cl and Mn. Symptoms of deficiency were observed in all cases, with the possible exception of Cu. Toxicity symptoms of the elements tested were also observed. As a rule, there was good agreement between abnormalities induced with those described in the literature for cereals. Dry matter production was affected in the following increasing order: -S = - Cu = - P = complete, -B, -Zn, -K, -Mo, -N, excess Mn, -Mg, excess Cl, -Fe, excess Al and -Ca. The following leaf contents correspond to deficiency level: N - 1.87%, P-0.14%, K-0.73%, Ca-0.40% (lower leaves) and 0.66% (upper leaves); S-0.16%; B-32 ppm (lower leaves) and 15 ppm (upper leaves), Cu-8 ppm; Fe-157 ppm (lower leaves) and 162 ppm (upper leaves); Mn-339 ppm (lower leaves) and 144 ppm (upper leaves); Mo-0.54 ppm; Zn-16 ppm. Leaf contents associated with toxicity symptoms were: Al-640 ppm; Cl-3.85%; Mn-1440 ppm, and, 1220, 2.37% and 445 ppm, respectively for lower and upper leaves. Nutrient requirements of weet sorghum were estimated to be in kg/ha: N-89.0, P-10.2, K-91.5, Ca-31.5, Mg-18.1, and S-11.6; in g/ha: B-90.0, Cu.61.0, Fe-1,704.0, Mn-256, Mo-2-4, and Zn-146. Only N and K significantly affected ethyl alcohol yield.

O presente trabalho descreve uma nova técnica para determinação direta do enxofre orgânico do solo. No método preconizado os solos são incinerados a 800°C, em tubos de porcelana, sob corrente de oxigênio. Os gases formados sao recebidos em solução de peróxido de hidrogênio e, em seguida, o excesso do oxidante é eliminado por ebulição. O sulfato formado é determinado pelo método colorimétrico do cloranilato de bário, mediante leituras a 308 molimicrons. Foram realizados estudos sobre vários fatores que podem influir no método e a determinação do enxofre orgânico em cinco solos, pertencentes a diferentes grandes grupos, mostrou uma precisão razoável.

This paper describes a direct method for determining organic soil sulfur. By the proposed method the soil is ashed in an eletric tube-furnace at 800°C in a stream of oxygen and the escaping gases were absorbed by oxygen peroxide solution. After the ashing the excess of oxygen peroxide is eliminated by ebullition, and the resulting sulfate is determined by the colorimetric method based on the reaction with barium chloranilate, and the absorbance was determined at 308 milimicrons. The results obtained allowed to conclude that the tech nique proposed is good and the accuracy satisfactory.

Neste trabalho são relatados estudos a respeito do método quelatométrico de determinação de sulfato, baseado na titulação do bário residual com solução de EDTA, após a precipitação do citado ânion na forma de sulfato de bário. Foram estudados aspectos relativos ao emprego de diferentes indicadores e passou-se a preconizar o uso de solução de púrpura de ftaleína a 0,2%. São descritos experimentos relativos à determinação de sulfato em soluções puras, observando-se o período de precipitação e a influência de diversos ânions. Finalmente, tendo por base os dados obtidos, é preconizada urna marcha analítica para determinação de enxôfre total e enxôfre-sulfato em material vegetal. Os resultados obtidos quando se empregou a técnica proposta na determinação de sulfato em materiais vegetais, foram comparados com aquêles fornecidos pelo método gravimétrico, baseado na pe-sagem do sulfato de bário.

The present work reports a study of the chelatometric method (by EDTA titration) for determination of sulfate in plant materials. A preliminary study about the indicator, conditions for the good precipitation of barium sulfate, and other influences on the method were performed. The presence of cations in the plant extracts did not cause interferences because they were separated using a cation exchange resin. The phosphate interferes and this ion can be removed by precipitation as ferric phosphate, adding ferric iron, acetate and ammonium hydroxide. Sulfate was determined in aqueous solutions, containing several ions, with good results. In order to compare the chelatometric (based in the proposed technique) and the gravimetric methods, in the determination of total sulfur in plants, five replications of different plant materials were analysed by both methods. The data obtained allowed to conclude that the technique proposed is good and the accuracy satisfactory. The determination of sulfur-sulfate was performed by the proposed method with satisfactory results.

O presente trabalho descreve a técnica de separação de cátions e ânions de solução pura, contendo os principais íons que ocorrem em material vegetal, mediante o emprego de coluna de resina trocadora de cátions Dowex 50 - X8. Foram estudados o efeito do pH na retenção dos cátions, a eluição destes e a sua recuperação, a lavagem da coluna de resina e a recuperação dos ânions. Mediante os resultados obtidos, foi possível estabelecer condições para o emprego da citada técnica na separação de cátions e ânions em extratos provenientes de material vegetal.

This paper describes a study about the quantitative separation of cations and anions of the aqueous solution contain ing ferric iron, calcium, magnesium, potassium, sulfate and phosphate, employing a column formed by a resin bed (Dowex 50 -X8). The cation retention was studied by using solutions of pH 1.85; 1.00; 0.60 and 0.20. The retention was good for the pH 1.85 to 0.60 for all the cations studied. The elution of the cations with three five mililiters portions of 4 N HCl solution showed good results. Sulfate and phosphate were recuperated after the solution was passed through the column of resin, washing the resin with two mililiters of water. The results obtained allow to conclude that the technique is satisfactory for the separation of cations and anions of the plant materials extracts.