Água inativa de alguns tipos de solos do estado de São Paulo

A retenção de água pelo solo se deve exclusivamente a fôrças capilares. Tôda divisão da água do solo é convencional. Quando se utiliza a equação y = xT / x + qT no estudo de processos que tendem para um valor final, a velocidade do fenômeno é dada por 1/q. Ê possível calcular para os solos do Estado de São Paulo a Umidade de murchamento por meio da Umidade equivalente. U. mu. = 0,68 U.Eq. Não se pode, em geral, aplicar com sucesso as fórmulas de Vageler e Alten para o cálculo do Hy em função dos trocáveis. O Hy do solo não se altera fazendo variar o tempo de secagem na estufa (105° - 110° C) antes da determinação. Os valores máximos dos dados referentes à água do solo foram encontrados na terra roxa legítima e os mínimos no Arenito Botucatu.
The retention of moisture by soil is conditioned exclusively by capillary forces. Any division of soil water is merely conventional. Using the formula y = xT / x + qT to compute the final value of a process, it is important to note that the velocity of the phenomenon is given by 1/q • For the major soil types of the State of São Paulo it is possible to calculate the wilting point by means of the moisture equivalent using the formula Wp. = 0,68 M.Eq. In general, the formulae of Vageler and Alten for computing hygroscopicity by means of exchangeable-ions are inadequate. Different periods of exposure of soils to temperatures of 105° - 110°C. before determinations are made do not exert a pronounced influence on hygroscopicity. The highest values for water-holding capacity were obtained in the terra roxa legítima and the lowest in the Botucatu sandstone

Estudo preliminar do sistema água-solo-planta no estado de São Paulo

Neto¹,

Jorge²

1947

A salinidade do solo em canteiros de estufa

Franco

1948

It has been noticed in the greenhouse of the "Instituto Agronômico de Campinas" that many species of plants developed poorly when planted in seed beds that have been repeatedly used without change of soil. In many cases even the seeds would not germinate in such seed beds. Experiments have showed that the; lack of normal plant development in these beds is the result of the increase in soil salinity. This salinity may be due to additions of fertilizers or to salts introduced in the ordinary applications of water. It was found that the soil solution had an osmotic pressure of 13.5 athmospheres at the wilting point. The tests showed that common bean (Phaseolus vulgaris L.) plants were more susceptible to the soil salinity than were the soybean and the corn plants. Floading of those seed beds several times resulted in the leaching of salts and the restoring of conditions favorable for normal plant growth

A água do solo e o sombreamento dos cafezais na américa central

Franco

1951

The coffee plant does not thrive well under shade in most of the coffee areas of the State of São Paulo, Brazil. It has been shown that water competition from the shade trees during the dry season is the factor responsible for the failure in growing coffee under shade in São Paulo. In all cases where the coffee plants were not thriving well under shade, the soil moisture after two to three months of drought was at the wilting point at the depths most utilised by the root systems of shade trees and coffee plants. In open plantations this was never observed. All commercial coffee plantations of Central America are shaded. Most of them are located in areas with a dry season as long as in São Paulo and some times even longer. A comparative study of the climatological factors, methods of cultivation and most common species of shade trees was made. No one of these factors explained the different behavior of the coffee plant under shade in Central America and in São Paulo. The available soil water was measured in many coffee plantations in Costa Rica and El Salvador after four months without apreeiable rainfall. In all cases it was' found that, the actual moisture percentage was considerably higher than the wilting point. The amount of available water held by soils in São Paulo and Central America does not seem to be significantly different, although this was not carefully determined. It is suggested that a comparative study of the moisture-tension curves of soils of São Paulo and Central America might explain the different behavior of the coffee plant with shade under these two different conditions. It is possible that, as a consequence of a much steeper moisture-tension curve, the plants in São Paulo soils transpire freely until the soil moisture reaches the wilting point. This would result in a rapid soil water consumption. If the Central American soils have a smoother moisture-tension curve, the Avater absorption and transpiration rate by plants may be slower and as a consequence the available water may last longer in the soil. The ratio of the moisture equivalent to the wilting point was found to be around 1.29 for the soils studied in the Meseta Central of Costa Rica, around 1.44 for those in El Salvador and 1.94 for the ashy soils in the vicinity of San Salvador volcano