6 The Bulletin. 



at a time, as this more than covered the middle, and an effort was 

 made to work over the plats as quickly as possible immediately after 

 rains to break the crust formed by the showers and leave a dust mulch 

 to check evaporation. The cultivator was run about II/2 to 2 inches 

 deep toward the close of the season. It was attempted to cultivate 

 every ten days, which had to be changed, of course, to suit the season. 



FERTILIZING MATERIALS. 



The composition of the fertilizing materials used in these tests 

 were as follows: 



Peruvian Guano. — The Lobos type was used, which contained on 

 an average of 22.49 per cent of total phosphoric acid; 3.18 per cent 

 of nitrogen ; and 4.33 per cent of potash. It was found by laboratory 

 methods that about half of the total phosphoric acid was in an avail- 

 able form. 



Acid Phosphate. — This material is made by treating finely-ground 

 phosphate rock with oil of vitriol (sulphuric acid). The acid phos- 

 phate used contained 16.86 per cent of total phosphoric acid; 14.29 

 per cent available phosphoric acid; 12.48 per cent of water-soluble 

 phosphoric acid, and 2.57 per cent of insoluble phosphoric acid. 



Kainit. — This is a crude potash salt, which is mined in ]^orth 

 Germany. The average composition of the kainit used was 12.01 

 per cent of potash. This material also contained from 30 to 40 per 

 cent of common salt. 



Manure Salt. — This material is also derived from the potash 

 mines of Germany. The manure salt used contained on an average 

 of 19.68 per cent of potash, the potash being chiefly in the form of 

 muriate. 



Nitrate of Soda. — This material is mined in Chili. The nitrate 

 used contained 15.16 per cent of nitrogen which is in a readily avail- 

 able form for direct use by growing plants. 



Dried Blood is a by-product of slaughter-house establishments. 

 Its nitrogen is as available or more so than that of cotton-seed meal. 

 The blood used was of a high grade and contained an average of 

 13.14 per cent of nitrogen. 



Cotton-seed Meal. — The cotton-seed meal used contained 6.67 per 

 cent of nitrogen and about 2.80 per cent of total phosphoric acid and 

 1.80 per cent of potash. 



Basic or Thomas Slag. — It is a bv-product obtained in the manu- 

 facture of steel by the modified Bessemer process. The lot of this 

 phosphatic material which was used in the experiments that follow 

 contained an average content of 16.23 per cent of total phosphoric 

 acid and 9.04 per cent of insoluble phosphoric acid. 



Ground Phosphate Rock. — The brown Mount Pleasant rock ground 

 to a fineness so that 90 per cent would pass through a 60-mesh screen 



