No. 7. DEPARTMENT OF AGRICULTURE. 453 



able nitrogen, is usually advantageous, in order to aid germination, 

 and also that the plant may not suffer hunger for nitrogen during 

 the period when it is unable to gather it from sources outside the soil. 



The Kind of Lime and Amount to Use. 



The amount and kind of lime to apply will depend upon circum- 

 stances, remembering that lime possesses many functions, all of which 

 need not necessarily be exercised in the preparation of land for 

 alfalfa. It is essential, however, that the neutralizing effect of lime 

 be exercised in order that the soil may become a favorable mi'dium 

 for the life and development of the organisms which do not thrive in 

 acid soils. The function of lime to convert dormant into active con- 

 stituents, for example, mineral compounds containing phosphates and 

 potash would, of course, only be effective on soils possessing large sup- 

 plies of inert plant-food, as clays and loams, whereas these functions 

 could not be exercised upon soils deficient in mineral compounds of 

 this class. The function that lime exercises in improving the physi- 

 cal character of soils is, also, important, improving their texture, mak- 

 ing heavy soils more open and porous, and light soils more compact. 

 Neither is the function of lime for acting upon organic vegetable 

 matter, setting free nitrogen, so important in the case of legumin- 

 ous crops, as cereals, because the plant is not dependent upon soil 

 nitrogen, and therefore any effect of lime which would result in a 

 too rapid development of available nitrogen would discourage, 

 rather than encourage, the plant to gather nitrogen from the air, 

 besides making them less absorbent of moisture. 



Iti may be said, as a broad general rule, that the use of lime is 

 mainly for the purpose of neutralizing acidity, improving physical 

 character, and feeding the plant with lime — the latter being a very 

 important matter, as alfalfa is more than any other a lime-loving 

 plant, and enormous quantities are annually removed. Hence, on 

 0<xht soils, which are usually deficient in phosphates and potash com- 

 pounds, mild or carbonate of lime, Avould be preferable to the use of 

 burned or caustic lime, although the caustic may be used quite as 

 safely upon soils of a heavy character, where it may exercise the 

 function of ."^etting free mineral plant-food. Experience and experi- 

 ment, both unite in showing that there is no real danger that an ex- 

 ces^ve amount of lime will be used. I think that as to lime a safe 

 guide as to the kind to buy is the cost per unit of actual lime, whatever 

 may be its kind. ^Ye do not yet know as much as we ought about 

 lime, but what we do know leads me to believe that whether we use 

 lime from pure limestone, from magnesia-limestone, from oyster shells 

 or shell marks, either burned or ground, will depend upon what actual 

 limo costs us delivered at the farm — nearly all costs too much at 

 present. 



Jos. E. Wiug, than whom no other is a safer guide, recommends at 

 least 4 tons of carbonate of lime per acre, and prefers 8 tons, and says 

 that wherever lime is used in sufficient quantity, not only is the 

 growth of the plant itself encouraged, but weeds very detrimental in 

 securing a permanent stand, as for example summer grass and crab 

 grass, are practically eliminated. His recommendation is to use the 

 ground limestone in preference to the burned lime. Our experience 

 shows that the burned lime, at the rate of one ton to the acre is good, 

 but that two tons are better, which would correspond with about 4 

 28—7—1908. 



