No. 6. DEPARTMENT OF AGRICULTURE. 406 



ter. This result is doublk'ss uccoiiiplished in part, by the direct de- 

 composiug action of this powerful reagent upon the humus; but the 

 principal destruction is probably accomplished indirectly by the in- 

 creased activity of bacteria induced by the greater alkalinity of the 

 soil. This power is highly useful in bringing the long accumulating 

 store of food in old meadow lauds and peat bogs ,and those of strawy 

 and green manures into available condition; but carried too far, it 

 lead© to a great waste of fertility and a serious injury to the spongy 

 texture of the soil. It is fortunately true, even w^here excess is used, 

 that the non-nitrogenous materials are reduced more rapidly than 

 the nitrogen, just as in the ordinary decay of humus; this was made 

 clear in the experiments conducted by the writer and reported in Bul- 

 h^tin Gl. Wheeler, Sargeant and Hartwell (17) have found the 

 same fact in experimenting upon the effects of lime and gypsum 

 upon the decay of humus. 



There remains for brief mention several direct chemical reactions 

 of lime with soil constituents. Its effect upon soil ammonia may 

 first be noted. When the chemist desires to test a substance for the 

 presence of ammonia, he tests it in a moist condition with caustic 

 lime; if ammonia is present, it is liberated and can be detected either 

 by its odor or its effect upon various coloring matters. Lime liber- 

 ates ammonia from its soil compounds, in like manner, whether it be 

 there contained with the acid of humus, with silica, or with the sul- 

 phuric acid of a fertilizer. The result of a gradual liberation is to 

 promote nitrification and crop growth; calcium carbonate also at- 

 tacks ammonium sulphate, forming ammonium carbonic and calcium 

 sulphate. If excessive quantities of either ammoniac or ammonium 

 carbonate are suddenly formed, a serious loss of these valuable con- 

 stituents is quite possible. 



Giustiani (18) found a distinct loss of nitrogen to occur when con- 

 siderable quantities of ammoniacal fertilizers were applied to calca- 

 reous soils, least when such soils were also moist and rich in humus; 

 but in the case of sands, even those containing 5 to 20 per cent, of 

 lime, such fertilizers may be beneficial unless drought supervenes. 



Lime likewise liberates potash from its combination with some 

 silicates; for this reason, a small dressing of potash salts on soils al- 

 ready fairly basic, may accomplish as much good as a much more ex- 

 pensive application of lime. 



Lime, whether in caustic or carbonated form, also reacts upon the 

 iron and aluminum phosphates in the soil, phosphates that are with 

 difficulty attacked by many plants, and combines wdth the phos- 

 phoric acid to form the much more available lime phosphates. 

 Furthermore, in soils well supplied with lime, soluble phorphoric acid 



(1?) Jour. Amer. Chem. Soc, 21, 1032-7. 

 (18) Ann. Agron., 27, 862. 



