124 EXPERIMENT STATION KECOED. [Vol.37 



0.6 per cent for sugar. No injurious influence of tlie sodium nitrate on the soil 

 .structure was observed. 



Tlie greatest difficulty encountered in tiie iise of sodium nitrate was the ease 

 with which it is leached out of the soil. It is considei-ed probable that on heavy 

 soils there was some loss of sodium nitrate through denitrification. For this 

 reason it is considered inadvisable to use stable manure with sodium nitrate on 

 heavy soils. In five tests on light soil the use of stable manure with sodium 

 nitrate or ammonium sulphate had no such injurious results. 



In four tests on soil rich in lime, ammonium sulphate gave better results than 

 sodium nitrate. In two tests in which molasses was used with ammonium sul- 

 phate and with sodium nitrate, good results were obtained in the former case 

 but not in the latter. In four tests on light and four tests on heavy soils, it 

 was found that ammonium sulphate can be partially replaced by sodium nitrate 

 with profit. 



It is considered, therefore, that the advisability of using sodium nitrate as a 

 substitute for ammonium sulphate on Java cane soils will depend mainly on the 

 cost or scarcity of the ammonium sulphate and the cost of sodium nitrate. 



The solubility of mineral phosphates in citric acid, II, G. S. Robertson 

 {Jour. Soc. Chem. Indus., 5.5 {1D16), Xo. 4, pp. 217-220; Chem. Ncics, IIJ, (11116), 

 No. 2978, pp. 295-29S).— Continuing previous work (E. S. R., 33, p. 313), ex- 

 periments with Makatea I.sland. Florida pebble, and Algerian, Gafsa, Tunisian, 

 and Belgian phosphates are reported, which led to the conclusions " that min- 

 eral phosphates are completely soluble in 2 per cent citric acid if a suflicient 

 number of extracts are made. In the majority of the rock phosphates exam- 

 ined five extracts removed from 90 to 1CK> per cent of the phosphoric acid 

 present. 



" Even a small amount i>f free lime or cahiuni carbonate decreases substan- 

 tially the solubility of mineral phosjihates as judged by the citric acid test. 

 When a large amount of calcium carbonate or free lime Is present, the citric 

 acid test, as commonly practiced, is a test for llnie and not for phosphate.^. 

 It is important In this respect to distinguish between free lime and calcium 

 carbonate and lime actually entering into the composition of the phosphate. 

 The higher the percentage of lime actually entering into the phosphate com- 

 pound, the higher the citric solubility of the pho.sphate Fineness of grinding 

 affects the total citric solubility of the mineral phosphates (judged by five 

 extracts) to the extent of aiiproximately 10 per cent decrease for each of the 

 gradients — passes '100,' refuses '100,' refuses '60,' ."ind refuses '30' sieve. 

 With one exception, calcining produces a marketl decrease in the citric solu- 

 bility of mineral phosphates. The longer the calcining (ontinues, the more 

 insoluble does the phosphate become." 



The results as a whole are taken to indicate Ihe worthlessne.ss of the citric 

 acid te.st as a means of judging the relative fertilizing values of pho.sphatic 

 manures. Mineral phosphates are considered as valuable as a .source of phos- 

 phoric acid for plants as basic .slag. 



Liming and lime requirement of soil, .J. W. Amks and C. J. Schollenberger 

 (Ohio Sta. Bui. 30G (1916). pp. 2H1-S96, figs. 5). — The work of others bearing on 

 the subject is briefly reviewed, and data obtained from several years" study 

 of fertility plats under various conditions of liming and treatment and the 

 results of certain pot experiments are reviewed and summarized. 



It was found that " the chemical comptisition and mechanical condition of 

 lime materials are probably of primary importance In relation to speed of 

 reaction with soil, rate of loss, and u.sefulness as soil amendments. The coni- 

 paratlvely small amounts of carbonate residual from applications of various 

 lime materials after relatively brief periods indicate that (lie speed of reaction 



