A method is described for the determination of the fluorine content of basic slag.

The fluorine content and the citric solubility of a number of basic slags are compared.

An account is given of a reliable technique that has been evolved for making dynamometer measurements in the field. It has been shown that quite small variations in the trace of the drawbar pull are significant, and correspond to actual variations in the resistance of the soil. No significant change in drawbar pull is produced by imperfect adjustments in the hitch or set of the implement within the limits met with in ordinary ploughing, except in so far as the depth of working is affected. The drawbar pull bears a linear relationship to ploughing depth within the region of ordinary ploughing. The slope of the land is without appreciable effect on the drawbar pull up to gradients of 1 in 40.

Measurements are recorded of soil resistance to ploughing, taken with a view to testing the uniformity of a soil over a single field. The results have been examined for significance and indicate large variations over short distances. The differences have been represented by means of isodyne contours (i.e. lines of equal drawbar pull), drawn on a map.

The importance is emphasised of assuming and allowing for such variations before drawing conclusions from the drawbar pull recorded by different implements.

Preliminary work is described showing that the variations are correlated with clay content and also with the growth of a crop in its early stages.

Using the conception of the “ideal soil” a calculation has been made of the cohesion due to the capillary attraction between the particles when wetted. Experimental verification of this theory is afforded by cohesion tests on the ignited silt fraction separated from soil.

1. An improved and simplified laboratory method of measuring the electrical conductivity of soils is described and measurements recorded for diverse soil samples.

2. The results for ignited soil lead to certain interesting confirmations of the capillary theory of an ideal soil.

3. The results for soils generally indicate a sufficiently simple connection between conductivity and moisture for this property to be made the basis of soil moisture determinations.

4. Certain clays were found to form a class apart, and must be regarded as exceptions to the general statement in (3) owing to the more complex nature of the moisture-conductivity relationship.

Maps of soil resistance to ploughing have been drawn up from the dynamometer readings over several seasons for the Rothamsted classical plots, carrying wheat, barley and roots respectively.

The conclusions as to the effect of manurial treatment are only of a general nature at the present stage of the work. Such differences are certainly small in comparison with the natural variations in the soil.

In the case of the Broadbalk wheat plots the drawbar pull values have been shown to have a close relationship with the clay content of the soil and with certain aspects of the soil drainage.