O.M. de Castro

Effect of several calcium sources on cation leaching using soil columns

No estudo realizado em colunas de solo montadas em laboratorio, procurou-se avaliar o movimento do calcio, e de outros cations, apos aplicacao de calcario agricola, gesso, calcario calcinado e uma mistura de calcario agricola e gesso, comparados com um tratamento testemunha, em dois latossolos vermelho escuros de texturas diferentes: media e argilosa. Utilizaram-se colunas de PVC, com 5cm de diâmetro e 45cm de altura, e aplicaram-se em cada coluna 1,8 litros de agua, parcelados em quatro vezes. Determinaram-se os cations trocaveis presentes na agua percolada e, no final do experimento, em cinco profundidades de cada solo. Os resultados mostraram que nos tratamentos gesso e calcario mais gesso as quantidades de Ca2+, Mg2+, K+ e Al3+ na solucao percolada foram maiores, enquanto que os tratamentos calcario agricola e calcario calcinado nao promoveram perdas significativas de cations. As maiores perdas ocorreram na primeira percolacao no solo de textura media e na segunda no solo de textura argilosa. O gesso nao modificou o pH dos solos, mas reduziu teores de bases no solo argiloso, enquanto que os calcarios corrigiram o solo apenas proximo a camada de incorporacao.

ALTERAÇÃO DE ATRIBUTOS QUÍMICOS DO HORIZONTE SUPERFICIAL DE UM LATOSSOLO E UM PODZÓLICO COM A CALAGEM

A calagem e essencial na agricultura moderna para aumentar a produtividade das culturas e a eficiencia do uso de adubos. A adicao de calcario normalmente altera atributos quimicos do solo. O objetivo do presente estudo foi verificar algumas dessas alteracoes no horizonte superficial de um latossolo vermelho-escuro argiloso e um podzolico vermelho-amarelo textura media/argilosa. Os atributos estudados foram: soma de bases, pH em H2O e KCl N, Al3+, H+, capacidade de troca cationica (CTC) a pH 7,0 e ao pH do solo, capacidade de troca anionica (CTA), fosfato e sulfato extraiveis, indice de adsorcao de P e disponibilidade de Fe, Mn, Zn e Cu. Com os dados obtidos pode-se concluir que a calagem aumentou o pH, a soma de bases, a CTC a pH do solo e o teor de fosforo extraivel; diminuiu o teor de aluminio, a relacao , a CTA e o teor de SO42- e nao alterou a CTC a pH 7,0, a adsorcao de P e o teor de micronutrientes.

Avaliação da atividade de microrganismos do solo em diferentes sistemas de manejo de soja

A greenhouse experiment was set up to evaluate the effect of different cultural practices on the activity of Bradyrhizobium japonicum and of other soil microorganisms involved in nutrient cycling. The soil used was from a field experiment that consisted of continuous soybean or corn-soybean rotations as summer crops, with oats or Crotalaria juncea as winter crops. Treatments totaled eight cropping system regimes includig the coventional and minimal cultivation. Soil from a nearby natural forest was used as control. There were six replicate pots for each treatment, three of which were additionally inoculated with K japonicum inoculum when soybeans were sown. Plants were harvested at flowering and shoot dry matter and nitrogen concentration were determined, as well as nodule number, nodule weight and percent mycorrhizal colonization of roots. Soil samples from each field treatment that had been kept in the refrigerator were evaluated to determine the total number of bacteria, fungi, cellulolytic microorganisms and nitrifying bacteria. Soybeans grown in soil from minimal cultivation plots and from crop rotations demonstrated significantly greater nodulation and larger cellulolytic populations. Other microbial groups were not highly affected. Percent mycorrhizal infection of roots was extremely low in all treatments, probably due to the high available phosphate levels in all soils.

Effect of two types of lime on some soil physical attributes of an oxisol from Brazil

Abstract Liming is a very important practice, especially in acid soils such as some Oxisols from Brazil, in which the chemical effects of liming are reasonably known. However, the effects of liming on soil physical properties are either not well known or, at least, controversial. In order to verify, under field conditions, the effect of liming on some soil physical attributes such us the aggregate stability, the water dispersible clay, the water retention were evaluated in a citrus liming experiment on a Dark Red Latosol (Typic Haplorthox) clay texture, from Cordeiropolis, Sao Paulo State, Brazil. The soil samples were collected in 0–10 cm and 10–20 cm depths, three years after the application of lime in the experiment, which had two replications per treatment. Calcitic and dolomitic limes were used with application rates of 0, 3, and 9 Mg ha‐1, with a total of five treatments, i.e., one control and two rates of application of each kind of lime. The results showed an increase in the aggregate stability. A...