摘要:

Using two calomel electrodes with variable KCl agar bridge concentrations the Donnan emf was measured for Volclay and/or Al2O3suspensions in equilibrium with KCl solutions of different concentrations. The sign and magnitude of the emf were found to depend on the ratio of KCl in the suspension to that in the bridge as well as on the sign and surface charge density of the particles.Small values for the Donnan emf were observed when the KCl concentrations in the calomel electrode bridges were low, though the Donnan emf was primarily dependent on the electrolyte concentration in the suspensions.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Water potential gradients were measured in soil-grown pepper plants. In one test where plants were equilibrated at low water potentials, the root zone water potential agreed well with water potential measurements in the plant stem and plant leaves. On the other hand it was found that the water potential in root-free soil adjacent to the root zone was higher than that in the root zone and that the observed gradient increased with decreasing root zone water potential. This increased gradient was attributed to decreased soil water conductivity in the root-free soil and to increased flow resistance across a millipore membrane separating the root-free soil and the root zone.In another test the total water potential in the root zone was controlled at three different levels by adding polyethylene glycol solution directly to the root zone. In this test the water potentials and water potential gradients responded in a reasonable fashion to the applied osmotic stress indicating that control of water potentials in soilplant systems is possible with polyethylene glycol.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Phosphorus, S, and Mo were applied alone and in all combinations on a grassland pasture deficient in P and Mo, and sown to subterranean clover (Trifiolium subterraneum‘Mt. Barker’). Effects on yield and chemical composition of the plants were observed for a 6-year period after treatment. During the first 2 years of the study, highest forage yields occurred where a combination of P and Mo were applied, and inclusion of S did not have an appreciable effect. The P-S treatment produced less forage than did P alone. Responses to S and Mo without P were relatively small. In the third, fourth, and fifth years there was a definite response to S where applied with P or P-Mo. The yield response to the three elements diminished with time.The percentage of P in the subclover increased with application of P and decreased with time where S and Mo were applied with the P. Application of S or Mo did no affect precent P in the clover where no P was applied.The SO4-S levels in subclover were increased by applying S. Both P and Mo treatments decreased S concentrations, which was probably a dilution effect. The SO4-S levels in subclover from plots fertilized with S decreased sharply in the first 3 years of the study.Molybdenum concentrations were increased in subclover by applying Mo, and reduced by applying S. There was an inverse relationship between concentrations of Mo and SO4-S, either comparing treatments in a given year or comparing years.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Simple and multiple correlation coefficient was run between soil pH, organic matter, available P, exchange K, Ca, Mg and nine other elements in the maize tissue sampled from four different soil zones of the Western and Lagos States of Nigeria. The results indicate that soil organic matter plays such a vital role that most of the soil nutrients are affected by its variability. When the soil has just come out of fallow, the soil organic matter, available P, exchangeable K, Ca, and Mg are very high. All these elements are leached down together as cultivation continues. There is an antagonism between exchangeable Mg, exchangeable Ca, and K. Since soil organic matter seems to furnish most of the exchange sites, it is not surprising that all the elements are significantly correlated with it. It therefore follows that the concentration, rate of release, and the amount of both major and micronutrients absorbed by plants are dictated by the level of soil organic matter.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID