This volume is part of the definitive edition of letters written by and to Charles Darwin, the most celebrated naturalist of the nineteenth century Notes and appendixes put these fascinating and wide-ranging letters in context, making the letters accessible to both scholars and general readers Darwin depended on correspondence to collect data from all over the world, and to discuss his emerging ideas with scientific colleagues, many of whom he never met in person The letters are published chronologically: volume 27 includes letters from 1879, the year in which Darwin completed his manuscript on movement in plants He also researched and published a biography of his grandfather Erasmus The Darwins spent most of August on holiday in the Lake District In October, Darwin's youngest son, Horace, became officially engaged to Ida Farrer, after some initial resistance from her father, who, although an admirer of Charles Darwin, thought Horace a poor prospect for his daughter

The Correspondence of Charles Darwin

Silica was separated from the oat plant by wet-way ashing and by dry-way ashing, examined under the petrological microscope and analyzed by chemical, X-ray and thermal techniques. Surface areas were also determined.

Studies of silica in the oat plant

1. Methods of investigating denitrification in soil are critically discussed with special reference to methods based on total-N analysis.2. A modified Kjeldahl method of determining nitrogen which includes nitrate and nitrite and is applicable to waterlogged soil is described and the use of this method in studies on denitrification in soil is illustrated and discussed.3. It is shown that rapid denitrification of nitrate in soil can be induced by incubating the soil under waterlogged conditions with organic materials such as glucose and that denitrification can be followed by total-N analyses if the organic material used to induce denitrification is not added in such excess that it also promotes significant fixation of atmospheric nitrogen.4. The percentage of added nitrate-N lost by denitrification on incubation of waterlogged soils with different amounts of nitrate and sufficient glucose for denitrification was found to be the same whatever the level of application of nitrate.5. Denitrification of nitrate in waterlogged soil containing glucose was found to be accompanied by a rapid but temporary accumulation of large quantities of nitrite and by the formation of smaller amounts of ammonia. Hydroxylamine could not be detected during denitrification, but it was found that this compound was rapidly decomposed in the soils examined by a process which appeared to be purely chemical.6. It is shown that denitrification of nitrate in soil is a microbiological process and that the viability of the micro-organisms responsible for denitrification is not affected by air-drying and storage of the soil.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0021859600032767

Denitrification in soil. I. Methods of investigation

A critical assessment of organic farming-and-food assertions with particular respect to the UK and the potential environmental benefits of no-till agriculture

In recent years more attention has been given to the polysaccharide fraction of the soil humus and some progress has been made toward an understanding of its nature and function in the soil. There is good evidence that it does contribute to soil aggregate stabilization. Its presence in the soil in relatively large amounts indicates relative resistance to decomposition. Methods for extracting and determination of total polysaccharides have improved but undoubtedly, still yield low results. Progress has been made in enumerating and quantitizing different structural units but it is not known whether (1) the soil polysaccharides consist of a mixture of numerous relatively simple plant and microbial polysaccharides at all stages of decomposition which are resistant to decomposition as such or become resistant through reactions with inorganic and organic soil constituents or, (2) whether the soil polysaccharides are new, highly complex polymers, consisting of numerous structural units, and which are naturally resistant to decomposition or become resistant through reaction with other soil constituents. Careful studies requiring new approaches and great ingenuity are needed to obtain more meaningful information on the structure, mechanisms of formation, and relationship to other soil constituents of the soil polysaccharide polymers. One rewarding area of research related to decomposition and binding action would be concerned with the recovery of soil polysaccharides (Finch et al., 1966). Relatively unaltered preparations should be obtained and freed from ash components. Further separation could be based on molecular weight distribution and relative concentration of uronic acid units. The preparations could then be used for binding or aggregation, adsorption and decomposition studies involving clays, soils, metal ions and humic acid preparations.

Decomposition and binding action of polysaccharides in soil

Soil Conditions and Plant Growth

AbstractCROP husbandry, the first occupation of man, which must ever remain essential to the maintenance of human life, has been pursued through all the ages as an art and a craft. The bearing of science upon it is a very recent development which is probably still only in its initial atages. Crops grow in vital association with two media, the air and the soil. It is barely a century ago that, following the discovery of photosynthesis, the main facts about the relationship of the crop to the air became generally known. The essential facts about the relationship of the crop to the soil are “still clouded in mystery. In spite of all the development in the study of plants on one hand and of soils on the other, very little is known of the relationship of one to the other, and we are still largely dependent upon empirical experiments in order to determine the effect upon the plant of any particular treatment of the soil. Moreover, as this account of the Woburn experiments shows very clearly, the successful conduct of empirical experiments is beset with great difficulties.Fifty Years of Field Experiments at the Woburn Experimental Station\n By Sir E. John Russell Dr. J. A. Voelcker; with a Statistical Report by W. G. Cochran. (Rothamsted Monographs on Agricultural Science.). Pp. xvi + 392 + 4 plates. (London, New York and Toronto: Longmans, Green and Co., Ltd., 1936.) 21s. net.

E. John Russell

Papers

Soil Conditions and Plant Growth

Fifty years of field experiments at the Woburn Experimental Station

World Population and Food Supplies