SOILS — FEETILIZEES. 517 



acid, 0.05 per cent of acid-soluble potash, and 1.96 per cent of total potash. The 

 yield of potatoes on this soil without fertilizer or manure declined more than 

 three-quarters in eleven years, and of rye more than one-half in twelve years. 

 With a rotation of potatoes, rye, and beets without manure there was removed 

 from the soil in twelve years 131.25 lbs. of phosphoric acid per acre, 329.G5 lbs. 

 of potash, and 334.64 lbs. of nitrogen. When the soil was fertilized with com- 

 binations of two of the essential fertilizer constituents the amounts removed 

 by the crops were 566.94 lbs. of phosphoric acid, 1,453.76 lbs. of potash, and 

 1,156.76 lbs. of nitrogen. It was found that the phosphoric acid and potash of 

 manure was better utilized than that of Thomas slag and potash salts, and this 

 was especially marked during the first years of the experiments. 



Bat guanos, P. L. Gile and J. O. Carreko {Porto Rico Sta. Rpt.l914,p. 16). — 

 Brief reference is made to vegetation tests which have been undertaken to 

 determine the availability of the phosphoric acid in the bat guanos of Porto 

 Rico. 



" The work accomplished so far shows that these deposits vary greatly in 

 chemical composition, but that there are several more or less well-defined types. 

 The vegetation tests show that the availability of the phosphoric acid also 

 varies greatly. 



" These deposits appear quite numerous and well distributed over the island. 

 There is probably no doubt but that the deposits can furnish valuable fertiliz- 

 ing material for certain districts of the island. The individual deposits, how- 

 ever, are probably too small and transportation on the island too costly for 

 the guanos to be exploited on any scale commercially." 



Fertilizer experiments on the red clay soil, P. L. Gile and J. O. Carrero 

 (Porto Rico 8ta. Rpt. 191Jf, p. U). — It is stated that the results of these experi- 

 ments showed that lime, sodium nitrate, ammonium sulphate, dried blood, a 

 nitrogenous and phosphatic fertilizer, and a complete fertilizer all failed to 

 increase appreciably the yield of cane on this soil. 



Drill fertilizing, Tacke (Mitt. Deut. Landw. Oesell., 30 {1915), No. 9, pp. 

 118, 119). — In experiments with rye, drilling fertilizers showed little advantage 

 over broadcasting. 



Production of nitrates from air, with special reference to a new electric 

 furnace, E. K. Scott {Jour. 8oc. Chem. Indus., 3^ {1915), No. 3, pp. 113-126, 

 figs. 10; rev. in Elect. Rev., 76 {1915), No. 1941, pp. 166, 167; Engin. Mag., 49 

 {1915), No. 1, pp. 104, 105, figs. 2).— The author describes and explains the 

 operation of his combined three-phase current furnace for the oxidation of the 

 nitrogen of the air, and shows why he believes it will considerably increase 

 the present yields of nitrogen compounds from this source. 



Potassium from the soil, C. G. Hopkins and J. P. Axjmer {Illinois Sta. Bui., 

 182 {1915), pp. 3-10, figs. 2). — Five years' pot experiments with clover and rape 

 on a brown silt loam and on the so-called insoluble residue obtained from diges- 

 tion of the brown silt loam for ten hours with boiling hydrochloric acid, having 

 a specific gravity of 1.115, are reported, the main purpose of which was to deter- 

 mine the extent to which decaying organic matter is able to liberate soil 

 potassium. 



The results indicate that after two years' green manuring sufficient potassium 

 was liberated from the insoluble residue to enable clover to be benefited by 

 lime and phosphate fertilizers so as to exceed the yield of crops on the normal 

 soil to which no such fertilizers had been added. The clover hay produced on 

 the normal soil contained about three times as much potassium per gram as 

 was contained in crops from the insoluble residue, which is taken to indicate 

 that the actual requirement of clover for potassium may be very much less than 

 has been estimated from the composition of hay grown on ordinary soils. It 



