596 AGRICULTURAL ANALYSIS 



The mechanical action of lime on soils tends to lighten heavy 

 clays and loams and to render firmer and more consistent the 

 light and shifting sandy soils. When a lump of clay is stirred 

 up in a bucket of rain water the water becomes muddy and re- 

 mains that way for many days. If, however, to the bucket of 

 muddy water a little lime water be added the suspended parti- 

 cles of clay begin to flocculate and soon the water is clear and the 

 clay falls to the bottom, nor does it again make the water muddy 

 for a long time when stirred up with it. The flocky character of 

 the precipitate is tenaciously retained and it is necessary to 

 knead the clay for some time to induce it to reassume its origi- 

 nal heavy character. An action like this takes place when lime 

 is added to heavy soils so that the soil becomes more porous and 

 assumes a better tilth on cultivation. With sandy soils an alto- 

 gether different action takes place. In making mortar, as is well- 

 known, sand is stirred in with water and lime and after being ex- 

 posed to air for a while the mixture becomes hard and firm, 

 the firmness increasing with age. This is due to the fact that 

 when the mortar dries the lime begins to absorb carbon dioxid 

 from the air and is converted into grains of carbonate which ad- 

 here strongly to neighboring sand grains and to each other so 

 that the whole soon gets to be a solid mass. Something like 

 this takes place in the soil and the sand grains are to some ex- 

 tent bound together. The increased firmness of the soil thus 

 gained is often of considerable advantage. 



Besides these actions, which are more or less mechanical, lime 

 exerts a chemical action on many soil constituents. Feldspar 

 and other common rocks contain potash, and this potash is in 

 such a form as to be inaccessible to plants. These rocks exist in 

 the shape of small particles in many soils and on them lime exerts 

 a decomposing action, setting the potash free. Lime also hastens 

 the decomposition of the nitrogenous organic matter and at the 

 same time renders the soil more retentive of the products formed. 

 The conversion of ammonia, resulting from the decomposition of 

 such organic matter into nitrites and nitrates, is not easily ac- 

 complished without a proper amount of calcium carbonate. The 

 microorganisms producing this change, which is known as nitri- 



