974 
Journal of Agricultural Research 
Vol. XXVIII, No. i 
In connection with the study of urephos, pots were included to test the effect 
of calcium sulphate on plant growth. This material behaved as an inert material 
on these soils, even with comparatively high applications. This study was 
included because in the manufacture of a material such as urephos, where cyan¬ 
amid is treated with sulphuric acid in excess, about 60 to 65 per cent of the 
fertilizer produced is calcium sulphate. 
The results with dicyanodiamide show that it is quite injurious to both beans 
and wheat and not merely inert. Its toxic effects were much more pronounced 
on crops grown on sandy soil than on clayey soil, as is almost invariably the case 
with any injurious substance. Even with the lightest application, the bean 
leaves turned yellow on the edges and the tips of the wheat blades were burned. 
With the heavy application, growth was far below normal and the lower bean 
leaves dropped off. (See PI. 1, C.) 
AVAILABILITY STUDIES WITH WHEAT 
A second series of experiments similar to those discussed above was conducted 
during the spring of 1922, using Norfolk sandy loam and Chester loam. The 
soils were not from the same lots as previously used, but were collected in the same 
general localities. Wheat was grown in all of the pots. The experiment was 
terminated six weeks after planting, earlier than intended because of a severe 
attack of mildew. The relative green weights of the wheat are reported in 
Table II. 
The wheat data show no very marked differences in the case of the Norfolk 
eandy loam between sodium nitrate, calcium nitrate, and ammonium sulphate at 
the two rates of application. The slight differences are within experimental error. 
Cyanamid, used alone, was much poorer than either of these, but the different 
combinations with calcium nitrate were all in a class comparable with calcium 
nitrate alone, or with the two fertilizers used as standards for comparison. Re¬ 
placing one-fourth of the cyanamid with calcium nitrate furnished a very satis¬ 
factory mixture, and where the two materials were used in equal parts the results 
were even better. Guanylurea sulphate was less satisfactory as a nitrogen carrier 
than any of the other materials, but did produce some increases, being about one- 
half as good as sodium nitrate at the largest rate of application and only slightly 
better than the control at the smaller rate. 
The increases in the green weight of wheat produced by the fertilizers on the 
Chester loam were much smaller with all of the treatments than on the Norfolk 
sandy loam. In general, however, the results already noted in the case of th£ 
lighter soil were also obtained on the Chester loam with the one exception, 
namely, that the mixtures of cyanamid and calcium nitrate were no better than 
the cyanamid alone, at the largest rate. It is difficult to explain this result, 
considering that the nitrogen applications were rather small for greenhouse work 
and certainly not sufficient to produce any injury on this heavier type of soil. 
The observations during growth agreed very well with the final green weights 
Cyanamid was somewhat slower to act than ammonium sulphate and the two 
nitrates, but the mixture of cyanamid and calcium nitrate showed quick 
responses. Guanylurea sulphate produced no toxic effects, but merely failed 
to increase the growth to any marked extent. 
The residual effects of the cyanamid applications on the two soils were negli¬ 
gible, the differences being within experimental error. The same was true of 
sodium nitrate at the two rates of application on the sandy soil, but on the loam 
there was a marked increase in yield over the control pots. Guanylurea sulphate 
increased the yield about 9 to 17 per cent on the sandy soil and 23 to 28 per 
cent on the Chester loam. These increases were much greater than with either 
