Desenvolvimento de um protótipo de pulverizador eletrohidrodinâmico. 2- Avaliação do seu comportamento no controle de trips (Enneothrips flavens) (Moulton, 1941) do amendoim (Arachis hypogaea L.).

Um prototipo de pulverizador eletrohidrodinamico foi comparado com um pulverizador com disco rotativo e com um pulverizador convencional, no controle de trips (Enneotrhips flavens, Moulton), atraves da aplicacao de deltamethrin em dois ensaios de campo. Os tres pulverizadores tiveram comportamento semelhante no controle do inseto, sendo que a producao de vagens do segundo nao mostrou diferencas estatisticas ao nivel de 5% de probabilidade entre os tres pulverizadores testados. O pulverizador eletrohidrodinamico mostrou vantagens logisticas devido ao menor volume de pulverizacao

Método do EDTA na determinação do cálcio e magnésio "trocável" do solo

This paper describes the determination of exchangeable calcium and magnesium in soil by using ethylenediamine tetracetic acid, after the separation of the principals interferents (iron, aluminum, manganese and phosphate) by using both ammonium hidroxide and ammonium sulfide in only one operation. In order to compare the chelometric and the permanganometric methods for determining exchangeable calcium, five replications of nine soils were analysed by both methods. The accuracy of the determination of exchangeable magnesium in soil was evalueted by means of the recovered magnesium, when the proposed method was applied. The data obtained in both studies allowed to conclude that the technique proposed is good and the accuracy is satisfactory

Determinação da capacidade de troca de cátions, do solo por fotometria de chama

O presente trabalho relata os dados obtidos sobre a determinação da capacidade de troca de cátions do solo, através da determinação do cálcio por fotometria de chama. A amostra de solo (2g) foi prèviamente saturada com íons cálcio, o excesso do reagente foi lavado e o cálcio deslocado do solo, mediante extração com solução normal de acetato de amônio pH 7. A determinação do cálcio, contido no extrato, foi feita mediante o emprêgo do fotômetro de chama Coleman modêlo 21. Os dados obtidos, demonstraram que a técnica adotada, além de sua simplicidade e rapidez, fornece resultados cuja precisão é satisfatória.This paper describes a method for determining cation exchange capacity of soils (C.E.C.).Two grams sample of 9 different soils were placed in a percolation tube with diammeter of 15 mm and lenght of 200 mm. Twenty mililiters of normal calcium acetate solution pH = 7,0 were percolated through the soil. Excess of calcium acetate was washed with ethyl alcohol 80% (80 parts of alcohol plus 20 parts of water, in volume) by suction. Adsorbed calcium was extratecd with 50 ml of normal ammonium acetate solution (pH - 7,0) by suction. Calcium extratecd by ammonium acetate solution was determined by photometry.The method described is very rapid and afford a good precision, according to table 1

Crop rotation and genetic resistance reduce risk of damage from Fusarium wilt in lettuce

Fusarium wilt of lettuce, caused by the soilborne fungus Fusarium oxysporum f. sp. lactucae, affects all major lettuce production areas in California and Arizona. In trials at UC Davis, we found that lettuce cultivars differ significantly in susceptibility to the disease, with some leaf and romaine types highly resistant under all test conditions. For more susceptible cultivars, disease severity is strongly influenced by inoculum levels and ambient temperature. Management of Fusarium wilt requires an integrated approach that includes crop rotation to reduce soil inoculum levels and the use of resistant cultivars during the warmest planting windows