1. From an examination of the compounds remaining in solution when humic matter is removed from alkaline extracts of Rothamsted soils by acidification, it is concluded that 30–40 per cent. of the nonhumic nitrogen is present in the form of peptides (proteoses, peptones and polypeptides), with 5 per cent, of free amino nitrogen and 12 per cent. of ammonia. The peptides are largely colloidal, and precipitated by basic lead acetate and by phosphotungstic acid. The remaining 40–50 per cent. of the non-humic nitrogen is mainly precipitated by basic lead acetate and is mainly non-basic.

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 edge rows give significantly higher yields than the inside rows, indicating thereby the inadvisability of using edge rows in yield trials.

(2) The variation between rows is very much greater than within rows. Different parts of the same drill row should therefore not be regarded as subject to independent error. The present investigation emphatically confirms Clapham's conclusions on this point.

(3) A slight advantage may be gained by the subdivision of the area to be sampled, without additional labour.

(4) In order to study the effect of the structure of a sampling unit of given size five types of unit have been examined. Of these, method (1), in which the “sampling unit” consists of four parallel half-metre lengths on adjacent rows, appears to be the most precise, and may be recommended on the basis of this trial. The half-metres within such sampling units appear to be negatively rather than positively correlated, and a significantly lower sampling error is obtained in consequence.

The preparation of natural humic acids from soil, peat (Dopplerite) and “Adco,” and of artificial “humic” acids from sucrose, cellulose, dextrose and glycine (Maillard), furfural, hydroquinone and lignin, and their purification is described.

Their elementary composition and their behaviour under conductometric titration with ammonia have been studied. The artificial products from sucrose and furfural did not behave as acids, but all the natural products, and the artificial products from cellulose, hydroquinone and lignin possessed the properties of colloidal acids.

Preliminary investigations into the “humification” of furfural and ω-hydroxymethyl furfural, and into the interaction of dextrose with amino bodies, are described.

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. The kneaded plate (plaque moulée) method of detecting deficiency in lime and available phosphate was applied to seventy-nine soil samples taken from the classical Rothamsted arable plots, and the Azotobacter population from some of these samples was estimated by counts on silica jelly.

2. The silica jelly counts showed that Azotobacter cells were very much reduced in number, or even absent in soil receiving 86 lb. per acre or more of mineral nitrogen. It is suggested that this is due to competition with other organisms whose growth is stimulated by added nitrogen compounds.

3. The kneaded-plate test correctly indicaṫed whether phosphate had been applied in soils receiving little or no nitrogen manures.

4. In those soils receiving 86 lb. or more of mineral nitrogen, the kneaded-plate test usually showed little or no Azotobacter growth even in the presence of phosphate and calcium carbonate. This failure was probably due to the paucity of Azotobacter cells originally present in such soil samples. In some cases the test was modified by inoculating the sample with a culture of Azotobacter and it then gave correct indications as to phosphate content.

The present communication deals with the results of quantitative investigations into the action of thermophilic cellulose-splitting bacteria on the fibre of a number of typical feeding stuffs. The primary object was to ascertain whether such measurements could form the basis of a quick in vitro method for estimating the digestibility of the fibrous constituent of feeding stuffs and, in addition, could lead to a method for following the process of lignification in herbage and in forage crops.

1. The consolidation in a light soil produced by sheep folding has been investigated.

2. The soil affected extended to a depth of 10 cm., the maximum compression occurring at a depth of 3–4 cm.

3. The consolidation produced was not totally destroyed by ploughing and was still apparent 5 weeks later when the seed was drilled.

A survey of some environmental and physiological factors influencing milk yield and an analysis of theories of and experiments on milk and butterfat inheritance have been made.

Further evidence is given of the fact that the proved dairy sire is the outstanding medium through which improvement in dairy cattle breeding may be effected. The need of (1) prolonging the breeding life of such an animal and (2) evolving a scheme for the regular progeny-recording of all dairy sires is emphasised.

The minimum number of unselected daughters necessary to give a reasonably accurate indication of their sire's transmitting ability is six.

1. A method for measuring the heaviness of a sample of soil is described which has the following advantages:

(i) The test can be completed in about 7 min; no initial drying, sieving or weighing is involved.

(ii) The apparatus is simple to construct and comparatively easy to work. The resultant figures are fundamental in nature, and not dependent on the dimensions of the apparatus used.

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.

The usefulness of soil analyses depends largely on the ease with which they may be compared with one another and, to this end, more or less successful attempts have been made to replace the ordinary columns of figures by a suitable graph, so that “he who runs may read.”

Sugar-beet seed germinates unsatisfactorily, largely because the true seeds are enclosed in tough woody coats. Experiments at Cambridge have been carried out to test whether treatments of the seed, which remove some of the coat, are beneficial. The general results indicate that such treatments are commercially sound, especially when seeding conditions are dry. Treatment with strong sulphuric acid, which can only be carried out by seed merchants, is effective: it accelerates and increases germination, giving a greater plant population at harvest, and this normally leads to larger yield. Increases up to 2 tons of unwashed beet per acre have been obtained.

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.

A method for determining the total exchangeable bases of carbonate soils is described. The carbonate in a known weight of soil is decomposed by acetic acid and the carbon dioxide evolved is estimated. By further extraction with acetic acid a solution is obtained which contains not only the bases originally in combination with the carbon dioxide but also the exchangeable bases. The amount of the latter is found by difference.

1. The equivalent parallel capacity and conductance of a series of soil blocks have been measured for decreasing moisture content.

2. The results obtained depend on the electrodes used. With mercury, all soils give curves of the same general type for the variation of the capacity with moisture because the capacity effects associated with the soil electrode interface are large compared with those due to the soil. The electrical properties of the interface have been shown to exhibit marked changes in their variation with moisture at certain moisture contents.

1. The total exchangeable bases, clay, total carbon and carbon oxidisable by 4 per cent, hydrogen peroxide, have been determined for a number of carbonate soils.

2. Assuming soils containing excess of carbonate under natural conditions to be base saturated, equations have been derived connecting exchange capacity with clay and (a) total or (b) “oxidisable” carbon content.

3. When the organic matter of these soils was assumed to have a constant base exchange capacity, no correlation was found between the exchange capacity of their clay fractions and either their silica-alumina or their silica-sesquioxide ratios.

4. Carbonate soils whose exchangeable base content was appreciably less than the calculated values were found to contain either small amounts of calcium carbonate (< 1 percent.), or the bulk of it was present in coarse form.

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.

The work recorded in this paper forms part of the general investigation on nutrition in relation to disease recently outlined by Orr, Macleod, and Mackie(1).

In this paper the general theory of the coagulation of dilute clay suspensions is discussed. The more important of the points considered are summarised below.

1. Two separate mechanisms causing collisions between suspended particles are considered, namely their Brownian motion and the mass motion of one group of particles relative to another group. Following Wiegner, these two types of collision are called perikinetic and orthokinetic collisions respectively. The rate of coagulation of a suspension is then shown to depend on the rate of collisions between particles and on the probability of adhesion between them when they collide. If this probability is unity, that is if every collision between two particles results in their adhesion, the suspension is undergoing rapid coagulation. There is excellent agreement between theory and experiment for this type of coagulation whenever the mathematical equations involved can be solved. But if the probability of adhesion is less than unity, the suspension is undergoing slow coagulation, and there is as yet no theory capable of giving the rate of coagulation of such a system.