Research Article
Studies in crop variation. I. An examination of the yield of dressed grain from Broadbalk
- R. A. Fisher
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- Published online by Cambridge University Press:
- 27 March 2009, pp. 107-135
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In Part I is given a survey of the results of a statistical examination of the yield of the plots of Broadbalk “Wheat field during 67 years. The main features of the comparison of mean yields are well known; the comparative rates of decrement, shown in Section 5, supply a class of facts well worthy of further study. Particularly striking are the relatively slow rates of decrement of plots 2b and 8, compared with plot 7, which would seem to show a permanent advantage in very high nitrogenous dressings, and to emphasise the need for caution in the application of the principle of diminishing returns. The evidence of the influence of potassium sulphate and its substitutes, sodium sulphate and magnesium sulphate, shown in Table V, is also very striking. An unsuspected feature of the changes of mean yields, which precludes the possibility of obtaining from these data true curves of exhaustion has appeared in the slow changes which have taken place in all the plots in a similar manner. In Part II the mathematical methods by which the variation has been analysed has been discussed, partly as a justification of novel procedure, partly, to make clear that the three types of variations found have been genuinely distinguished. In Part III such evidence as is available has been presented, in order to throw light upon the possibility that the changes in mean yield have been caused by variations in the prevalence of weeds at different periods.
One point of importance which should be emphasised is that average wheat yields, even over long periods, from different fields or for different seasons cannot approach in accuracy the comparison of plots of the same field in the same seasons. The advantage of the method adopted by Lawes in the permanent experiments which he instituted is very evident. The effects of weather clearly require that the seasons should be identical, unless the series be very long, but the slow changes in mean yield show that even comparatively long series of different years from the same field cannot be accurately compared. Within the same field, however, the slow changes have almost proportional effects, and comparison between the mean yields of neighbouring plots may be made with great accuracy. The only case in which changes in mean yield sensibly affect the comparison of averages is that of plots 17 and 18. In comparing these with plots 3 and 4, 5, 7, and 10, it would be more accurate to confine attention to high yielding periods, at which the disturbing causes are at their minimum.
It is believed that the deviations from the smooth curves, which have been freed, for the most part, from the effects of exhaustion and weeds, form statistically homogeneous material for the study of meteorological effects.
Dephenolisation in soil
- Nagendra Nath Sen-Gupta
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- 27 March 2009, pp. 136-158
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1. Two colorimetric methods of estimation of phenol and the cresols in soil have been developed,—one for small quantities down to 0·01 mgm. in 50 c.c. of the soil distillate, and the other for larger amounts of the substances.
2. It is found that, even by starting the distillation of the soil within 20 minutes of the application of phenol, a 100 per cent. recovery of the added phenol cannot be effected, except in the case of autoclaved or steamed soil. This instantaneous disappearance is followed by a further loss, slower and different in character.
Phenol and the three cresols disappear, with more or less ease, in all soils examined.
3. The slow disappearance is apparently largely brought about by micro-organisms which are capable of decomposing phenol. There appears, however, to be some non-biological action also, since the disappearance in unmanured soil poor in micro-organisms, besides being much slower than in manured soil, is altogether different in character.
4. Autoclaving the soil at 130° C. for 20 minutes destroys the cause or causes of disappearance altogether, but the action proceeds, although much more slowly than in untreated soil, in the presence of a considerable amount of toluene and mercuric chloride. Further support is thus given to the view that a non-biological action accompanies the biological decomposition.
5. Partial sterilisation by treatment with toluene which was evaporated before the addition of phenol increases the rate of loss, but steaming does not.
6. The disappearance takes place even in soil air-dried to 2·4 per cent. moisture, but it is extremely slow compared with the rate in normal soil.
7. By applying a number of successive doses of phenol to the same soil it has been found that each dose disappears at a higher rate than the preceding one. This is entirely in accordance with an action mainly biological in character. The same effect has been observed in the case of m-cresol.
8. Two types of bacteria have been isolated from soil which are able to decompose phenol in culture solutions containing mineral salts and phenol. A third type capable of decomposing m-cresol has also been isolated from soil. A detailed study of the isolated organisms is being made in the bacteriological laboratory.
9. The instantaneous disappearance of phenol occurred in all soils examined. Its cause appears to be non-biological, but its exact nature has not yet been elucidated. There is reason to believe that the loss varies with the clay content of the soil. The loss does not appear to be materially affected by the period of contact of phenol with the soil prior to distillation, and is presumably complete only when the soil (air-dry) has been uniformly moistened with steam. Up to a certain point the loss is proportional to the concentration of the phenol solution.
10. The factor causing the loss is destroyed by autoclaving the soil at 130° C. for half an hour or by steaming it at 100° C. for one hour.
The treatment of the soil with sulphuric acid (50 per cent. by volume) either before or after addition of phenol greatly augments the loss, which may amount to 90 per cent, in case of phenol and 96 per cent. in case of m-cresol. This loss is not affected by autoclaving the soil.
11. Thus there appear to be at least three processes whereby phenol disappears from soil: one biological, one instantaneous chemical or physical and a third slow, chemical or physical. The mechanism of these changes, however, has not been elucidated.
This work was carried out during my tenure of the Earl Grey Memorial Fellowship awarded me by the Council of Armstrong College to whom and also to the Lawes Agricultural Trust I wish to express my thanks for facilities for carrying out this work.
My best thanks are due to Dr E. J. Russell at whose suggestion the investigation was undertaken and under whose direction the work has been carried out: and to Mr. H. G. Thornton for assistance on the bacteriological side.
Inheritance in barley. II. The awn and the lateral floret
- F. L. Engledow
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- 27 March 2009, pp. 159-196
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Some interesting contributions to this subject have appeared during the past three years. They contain somewhat discordant ideas and it has therefore been concluded that the present time is suitable for a brief review of the whole matter and for the publication of further experimental results. A striking susceptibility to environmental change is evinced by both the awn and the lateral floret, and it is part of the purpose of this paper to describe the nature of the fluctuations involved and to indicate the extent to which they militate against the reliable determination of genetic ratios.
A contribution to the investigation into the results of partial sterilisation of the soil by heat
- Viscount Elveden
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- 27 March 2009, pp. 197-209
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The discovery that partial sterilisation by heat is capable of greatly increasing the fertility of the soil, opens up possibilities full of interest both to agriculturist and to horticulturist. Steaming the soil has already become a common practice by growers of tomatoes under glass, where the soil in the houses when “sick,” that is, infertile no matter how heavily manured, is treated with steam, whereby its fertility is completely restored.
Front matter
AGS volume 11 issue 2 Front matter
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- Published online by Cambridge University Press:
- 27 March 2009, pp. f1-f2
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