The Relations of Lime to Soil Improvement. 631 



sible to attain the same degree of fineness by grinding that is attained 

 by burning and slacking. Seventy-five per cent, at least, of the 

 ground material should pass a 100 mesh screen. The larger the per- 

 centage of coarse material the larger the amount necessary to get the 

 same net effect. Considering composition and fineness, 50 pounds of 

 lump lime is equivalent to 



60 pounds hydrated lime. 

 100 pounds air-slaked lime. 

 250 pounds ground limestone or marl. 



Coarse, lumpy lime when present even in large amounts is of rela- 

 tively little value in the soil. Its physical condition is bad. Just here 

 it may be well to say that much of the so-called " agricultural lime " 

 is of too poor quality, owing either to physical or to chemical condi- 

 tions, to be used in construction. The chances are that it is equally 

 poor for agricultural purposes and we do not consider it to be to the inter- 

 ests of either the farmer to buy or the manufacturer to sell the material 

 on a blanket statement. It may be very useful and there may be 

 an eciuitable basis for its purchase and use, but such material should 

 stand entirely on its condition and content of calcium and other food 

 constituent. The farmer can afford to purchase the best commercial 

 lime if he needs lime. Any other arrangement is an adjustment to 

 special circumstances. 



5. The character and condition of the soil relate to the texture and 

 composition. Clay soils are more likely to need lime than are sandy 

 soils. Clay soils appear to be somewhat more affected physically by 

 caustic or hydrated than by carbonated lime. On the other hand, the 

 availability of lime carbonate is greater in a soil rich in decaying organic 

 matter than in one deficient in that constituent. For this and oiJicr 

 reasons it is eshecially important to couple organic manures with the use 

 of lime. They supplement each otiier and together bring out the best 

 effects of both. Soils rich in humus can stand more lime than these 

 deficient. Clay soils will stand more tlian sandy soils without injury. 



The leguminous crops arc more respon.^ive than other crops to 

 lime. Because of their relation to nitrogen-storage, they are a large 

 factor in soil upbuilding. Conse(|uently we see the advantage of the 

 coml)ination and the futility of their se])arate use in most cases. 



The I'nited .States Bureau of Soils studied under unifonu condi- 

 tions in wire baskets, 220 different soils fro:ii all parts of the country. 



