64 



All of the soil extracts were tested for sulphates, and 

 it was found that each soil to which sulphur was added 

 contained much more sulphates than the untreated 

 soil. However, quantitative determinations were not 

 made. The oxidation of sulphur increased the amount 

 of soluble manganese in each of the soils used; and in 

 several the amount made soluble was relatively large. 

 In both of the soils from Pennsylvania and in three of 

 the soils from Alabama, above 100 p. p. m. of manga- 

 nese were made soluble. The smallest amount found 

 in the treated soils was 28 p. p. m. Calcium carbonate 

 added at the rate of 1 per cent completely prevented 

 the solution of manganese. The results indicate that 

 soils in need of sulphur fertilization should be well 

 limed, unless already supplied with lime, if injury from 

 sulphur application is to be avoided. Further, it is be- 

 lieved that these results explain the sterility of Shedd's 

 soil to which large amounts of sulphur were applied. 

 Manganese, aluminum, or iron, in the form of sulphate, 

 very probably cause sterility, rather than free sulfuric 

 acid. 



The Toxicity or Field Soils to Which Different Ni- 

 trogenous Fertilizers Have Been Applied 



As stated in the introduction, 16 plots on the Ala- 

 bama Experiment Station Farm have been devoted to 

 a field study of the rate of nitrification of dried blood, 

 cottonseed meal, and calcium cyanamid, beginning in 

 the spring of 1913. The area occupied by these plots 

 is very uniform, and is nearly level. The surface soil 

 is very sandy and has a low water capacity. The 

 subsoil is a yellow sandy clay with a much higher water 

 capacity than the surface soil. Soluble salts are very 

 readily lost from this soil by leaching, as shown by 

 unpublished results. 



The fertilizers given these plots are in sufficient 

 amounts to furnish nitrogen at the rate of 77 pounds 

 per acre. All fertilizer has been applied broadcast, 

 and either disked or plowed in. Since 1915, applica- 

 tions have been made in both spring and fall. 



Each crop is grown continuously on the same set of 

 plots. With the exception of the first year, one-half of 

 each plot has been fallowed both winter and summer. 

 A winter cover crop of oats has been planted on the 

 cropped ends of all plots most of the years. 



