Orlando Melo de Castro

Atributos físicos do solo e crescimento radicular de soja em latossolo roxo sob diferentes métodos de preparo do solo

Soil pans caused by tillage operation may restrict root growth thus reducing yield. Physical properties of soil such as bulk density and soil strength have been used as parameters for management decision in order to promote root growth. This work was carried out to evaluate the relationship among these soil parameters and root growth, in a 7 year field experiment with five soil tillage systems and soybean (Glycine Max L.). The tillage systems combined summer and autumn tillage with disk harrow, chisel plow and no-tillage treatments. Higher soil strength and bulk density were observed in no-tillage system in the 0-0.3 m layer and in conventional tillage in the 0.1-0.2 m layer. Root density was higher in no-tillage treatment compared with disk harrow treatment. Root concentration in the upper 0.1 m were of 50% at the disk harrow, 30% at the chisel plow and 40% in the no-tillage. Below 0.3 m there was no significant difference among the tillage systems for all parameters. Reduction on root growth was found when bulk density and soil strength were higher in the 0.1-0.2 m layer and the rate between 0.1-0.2 and 0-0.1 m layers were high.

Desempenho de semeadoras-adubadoras de soja em Latossolo Vermelho muito argiloso com palha intacta de milho

Como a dificuldade da semeadura da soja sob grande quantidade de palha do milho safrinha intacta, sem a fragmentacao ou incorporacao dos residuos, em solos muito argilosos, tem desmotivado a utilizacao do sistema plantio direto pelos agricultores da regiao paulista do Medio Paranapanema, objetivou-se, com este trabalho, comparar o desempenho quanto ao embuchamento, bem como avaliar a qualidade da semeadura entre semeadoras-adubadoras original e adaptada, na cultura da soja. O sistema modificado proporcionou menor numero de paradas do conjunto trator-semeadora, em funcao de embuchamento. As frequencias de solo exposto e profundidades de deposicao da semente e do sulco em ambas as semeadoras e, ainda, o numero de plantas emergidas para a semeadora-adubadora modificada, apresentaram diferenca significativa entre as linhas de semeadura. O desempenho das duas semeadoras-adubadoras avaliadas nao foi satisfatorio quanto a largura de revolvimento do solo e a uniformidade da profundidade de deposicao da semente.

Atributos físicos e químicos de um latossolo vermelho eutroférrico sob diferentes sistemas de preparo

The objective of this work was to evaluate the effect of different soil tillage systems on soil physical and chemical attributes and their relationships with root development of maize (Zea mays L.) crop. The experiment was conducted at the Campinas Experimental Center of Instituto Agronomico, located in Campinas, SP, Brazil. The measurements were made during the 1990/91 summer cropping season when the field was cultivated with the cultivar C-606 of mayze crop. The tillage systems evaluated were: no tillage, soil tilled with chisel plow, and conventional soil tillage with disk plow and harrow, in plots measuring 7.5 m by 15.0 m, with three replications each. The soil physical and chemical attributes evaluated were: bulk density, soil penetration resistence, infiltration rate, hydraulic conductivity, organic matter, phosphorus, potassium, calcium, magnesium, pH and base saturation. The maize crop root density was determined using the auger method. The soil under no tillage showed the best soil fertility of the layer 0,0-0,1 m as compared to the soil tilled treatments. At the layers bellow that depth, the effect was the reverse. However, these differences did not affect the maize crop root development. The measured soil physical attributes allowed the identification of higher density layers caused by depth and repetition of mechanical operations of soil tillage, which contributed to reduce the maize root density.

Variabilidade espacial das precipitações pluviais diárias em uma estação experimental, em Pindorama, SP

Estudou-se a variabilidade espacial das chuvas diarias em uma escala reduzida em Pindorama, Sao Paulo, Brasil, utilizando dados que cobriram um periodo de 32 anos. Os dados historicos de cinco pluviometros, cujas distâncias entre si variam de 257 a 3.900 metros, foram submetidos a analise de correlacao para determinar a variabilidade espacial. A medida que a distância entre os pluviometros aumentou, o coeficiente de correlacao dos dados de chuvas por eles medidos diminuiu, revelando que a precipitacao pluvial depende das posicoes onde se localizam os pluviometros. As medias diarias mostraram que pluviometros proximos, porem sob maiores variacoes de altitude, possuem diferencas superiores a pluviometros mais distantes, mas sob altitudes similares. Quanto ao comprimento da serie, evidenciou-se que, para o estudo, as series deveriam possuir no minimo sete anos.

Atributos físico-hídricos de um Latossolo Vermelho eutroférrico sob diferentes sistemas de manejo

The objective of this work was to evaluate the behaviour of soil physical attributes of a Ferralsol under different management systems. The experiment was conducted at the Centro Experimental Central, Instituto Agronomico (IAC), located at Campinas, State of Sao Paulo, Brazil, during the years of 1990-1991. The soil of the area is a Ferralsol, managed with no-tillage, chisel plow and conventional tillage. The experiment was conducted in the field in plots measuring 7.5 x 15.0 m, with three replications for each management treatment. Analyzed soil physical properties were: water retention, aeration capacity, available water capacity, bulk density and hydraulic conductivity as a function of the water content (θ), through the instantaneous profile method, with evaluation of the water redistribution the soil profile for the different management systems. It can be concluded that: the chisel plow treatment showed greater water retention in the surface layer because of its greater soil porosity; soil hydraulic conductivity did not show significant differences between the three soil tillage treatments studied at the surface layer, whereas for deeper layers no-tillage system presented larger values of hydraulic conductivity as compared to the other treatments.