Two series of trials have been carried out to compare the digestibility of fresh grass with the material obtained by drying grass, from the same source and cut at the same time, in a band drier by heated air at an inlet temperature of 200° C.

This process has not affected the digestibility of the various constituents with the possible exception of the crude protein which is slightly depressed.

In the second series of trials a drier operating with air at an inlet temperature of 600° C. was also used. In this drier a depression of the digestibility of the constituents of the grass was noted. This was particularly so in the case of the protein which was depressed to a very marked degree.

It would therefore appear that although the use of the higher temperature increases the output of the drier, it adversely affects the digestibility of the final product.

Hay of excellent quality and high digestibility has been made by a process of artificial drying in which a current of warm air is blown through the grass in a stack. The air is heated by a system of hot-water pipes round which the stack is built.

The resultant product was of much greater feeding value than good meadow hay or seeds hay and was made at a season of the year when hay-making conditions were poor.

The economics of the process have not been worked out.

1. The mineral content of pasture as grazed under the Intensive System of Grassland Management has been examined. The pasture samples were collected from two centres in 1927 and from one centre in 1929. Magnesium, manganese, iron, sulphur and chlorine were determined in addition to the more common elements.

2. The mineral content of intensive pasture is equal to that of the best type of pasture produced by other systems of management, and superior to that of average good cultivated pasture in Great Britain.

3. The seasonal variations of the soluble ash, potash, soda and phosphoric acid depend principally on the climatic conditions.

4. The effect of drought at one centre has been to lower the percentages of soluble ash, potash and phosphoric acid.

5. Correlations exist between nitrogen and phosphoric acid, and soluble ash and potash. There is no evidence of further correlations between the constituents.

An experiment was carried out in 1929 and 1930 to obtain a measure of the effects of nitrogenous fertilisers used in combination with rotational grazing, on grass adequately supplied with phosphates, potash and calcium. A comparison of the two years has shown that the magnitude of these effects is governed by climatic conditions, and in the absence of a sufficient supply of moisture the increase in the quantity of herbage produced is reduced.

The results so far recorded in this series of investigations are discussed in their bearing on the hypothesis according to which the humic matter of soil is derived from lignin.

This hypothesis is supported, but since the artificial product prepared from lignin is nitrogen-free, whereas the natural product contains nitrogen, further progress in the elucidation of the nature and origin of humic matter is dependent on a study of the part played by nitrogen in the formation of humic matter, and the form in which it occurs.

The alkali-extraction of the nitrogen from soils of certain plots of the classical permanent experiments on Barnfield and Broadbalk at Rothamsted, follows a closely similar course to the alkali-extraction of carbon from the same soils.

1. The work described in the present series of papers was undertaken with the object of ascertaining the best conditions for the use of calcium cyanamide and of comparing it against older nitrogenous fertilisers. Earlier work has in part been repeated so as to ascertain whether the recent improvements in manufacture have overcome the difficulties encountered with the pre-War product.

2. The decomposition of cyanamide to urea can be brought about by a number of minerals likely to occur in the coarser fractions of the soil. The decomposition of cyanamide by soil proceeds according to a logarithmic law such that the rate of disappearance is proportional to the concentration of cyanamide in the soil water.

1. Calcium Cyanamide (the commercial form of Calcium Cyanamide) markedly increased the bacterial numbers of soils in uncropped pots and both the bacterial numbers and carbon dioxide production in flasks under laboratory conditions.

2. Improvements in the aeration of soil cultures in the laboratory not only increased the numbers of bacteria and accelerated the production and disappearance of ammonia but reduced the initial nitrification lag and increased the final accumulation of nitrate from Calcium Cyanamide. Urea formed from Calcium Cyanamide disappeared much more quickly in soils aerated by daily shaking than in undisturbed soils.

1. On storage under good farm conditions Calcium Cyanamide gained steadily in weight, the increase reaching about 10 per cent. after 27 months. The percentage of nitrogen decreased at a practically equivalent rate, so that there was little change in total nitrogen. The form of the nitrogen remained practically unchanged for the first 6 months; by 12 months there was a slight reduction in cyanamide nitrogen and a slight production of dicyanodiamide—less than 1 per cent. of the total nitrogen.

2. In a farm mixture of Calcium Cyanamide and superphosphate (1:3) cooled by spreading in a thin layer after mixing, 16 per cent, of the nitrogen was converted to dicyanodiamide in the fresh mixture and this increased to 25 per cent, after 1 month's storage. More dicyanodiamide was produced in a series of laboratory mixtures of Calcium Cyanamide and superphosphate, in which heating was allowed to take place. Dicyanodiamide production varied regularly with the composition of the mixtures, rising to a maximum of 50 per cent. of the total nitrogen in the mixture containing 20 per cent. of Calcium Cyanamide, and falling to below 20 per cent. of the nitrogen in the 50 per cent. mixture.

1. An attempt to maintain the health of a stock of Scotch seed Majestic in England is described.

A small stock of seed obtained direct from Scotland was split up into three equal portions A, B, C, which were grown isolated from each other and all other potatoes for three years (1927–9).

A. Remained unrogued.

B. Had all plants showing virus disease symptoms rogued out and the requisite seed saved from the remaining plants when mature.

C. Had a similar quantity of seed saved from ostensibly healthy plants when immature.

2. In a final chequer board yield trial fresh Scotch “stock” seed, which can be assumed to be above the average of ordinary Scottish seed, beat stocks A, B and C significantly. There was no significant difference in the yields from the stocks obtained by the two methods B and C and both stocks beat the mature unrogued stock A significantly.

1. A uniformity trial with potatoes was used for investigating the effect of size and shape of plots on the precision of field experiments. Up to a certain limit the S.D. in per cent. of the mean decreases when the size of plots is increased; further increase of plot size increases the errors as a lesser part of the soil variation can be removed.

2. Two-row plots show less variation than either 1 or 3-row plots. This may be explained by row competition.

3. When the area to be used is fixed, smaller plots are more efficient than larger, owing to the greater number of replications in the former case. One exception occurs in the case where border rows are not harvested; here 4-row plots are more efficient than 3-row plots, owing to the fact that a larger part of the soil is included in the calculations when 4-row plots are used.

4. Long and narrow plots are more efficient than shorter and wider of the same size. The only exception is again explained by row competition.

5. In field experiments with potatoes fairly large plots should be used; at least 2 rows wide and preferably long and narrow strips.

The present investigation consists of the statistical analysis of a uniformity trial with potatoes conducted by Dr Kirk. In this study the standard error in per cent. of the mean decreased slightly with the increase in the widths up to plots 5 rows wide, but any further increase in the width of the plot resulted in the higher standard error. The fertility contour map of the field is given in Fig. 1 to show graphically the effect of soil heterogeneity on the yield. The increased size of the plot resulted in the decreased efficiency in the use of the land when the entire plot was harvested; in other words, given a piece of land of certain size, it is advantageous to have a greater replication of smaller plots than a smaller number of larger plots. Four-row plots proved to be the most efficient when the border rows are discarded. The superiority of long and narrow plots over shorter and wider ones is demonstrated.

With the greatest pleasure I acknowledge my indebtedness to Dr Kirk, who supplied me with the data, to Dr Fisher for his valuable suggestions and to Dr J. Wishart for useful advice and criticism.

1. Samples of tea leaf from different portions of the same field were analysed for ash, nitrogen, potash and phosphate on thirty-five consecutive plucking rounds extending over a period of seventeen months for which yields were also recorded.

2. The significant variations obtained are shown to be partly due to seasonal differences which affect all the constituents and to persistent differences between portions of the field in the case of yield, ash and potash. No significant differences were detected between the nitrogen and phosphate status of different portions of the field, although the sampling errors were not larger than those of the former category.

3. These results indicate that the sampling technique is satisfactory, a point of some importance in view of laboratory investigations on tea manufacture, and confirm the finding from other considerations that the standard of plucking can be maintained at a reasonably high level.

1. Pyrethrum powders and dusts, prepared by grinding or by the incorporation of extracts of pyrethrum flowers upon absorbent earths, such as talc and kieselguhr, lose their insecticidal activity on exposure to light and air. The loss is more rapid in the case of artificially prepared dusts than with ground flower-heads.

2. Both light and air play an important part in the process of inactivation, as samples of kieselguhr-pyrethrum and talc-pyrethrum dusts stored in closed vessels in the dark or exposed to air in the dark are relatively stable; also samples exposed to light in an atmosphere of carbon dioxide, nitrogen or in vacuo lose little of their toxicity under the same conditions of illumination; samples exposed in oxygen, however, rapidly lose their activity.

3. Both wet and dry oxygen were effective in destroying the activity of the dusts, but apparently at different rates, and there is some suggestion that the type of reaction may be different in the two cases.

The unsatisfactory nature of empirical formulae for the determination of surface area in metabolism work, especially with reference to pigs, is discussed, and the conclusion reached that the actual estimation of the area is the only satisfactory method where an accuracy greater than ± 10 per cent. is desired.

It is pointed out that surface area is to some extent variable in animals and that direct determinations are from this point of view less satisfactory than might have been thought.

A new method is proposed for estimating the surface area of a pig in a definite standing position depending on mathematical and photographic conditions only, and therefore applicable to the living animal, and to the same animal at different times during its life. Full sets of computations are given and one case is noted where the method affords a correct estimate as between two pigs where the formulae are all clearly wrong.