MINERAL MATTER FOR CORN LAND 149 



on plats where lime was used alone and where it was used in 

 connection with other fertilizers. In commenting on 

 results with lime, Director Thorne says : — 



" Taking the results as a whole, it would seem that the 

 lime has performed two distinct offices in this test : in the 

 first place, it has increased the yield by an average of 

 about 10 bushels per acre, or 30 per cent of the unfer- 

 tilized yield. This it must have done in one or both of 

 two ways ; either it has furnished a needed element of plant 

 food to the growing crop, or else it has rendered the plant 

 food already in the soil more available, either by direct 

 chemical action of the lime itself on the soil stores of nitro- 

 gen, phosphorus, and potassium, or by opening up the soil 

 and giving the air, water, and frost a better opportunity to 

 reach these stores and prepare them for plant nutrition. 



" The other office performed by the lime seems plainly 

 to have been the setting up of conditions favorable to the 

 growth in the soil of the micro-organisms by which the 

 stores of organic nitrogen are gradually converted into 

 available form through the process of nitrification. This 

 is indicated by the fact that the giving of large quantities 

 of available nitrogen in the fertilizers appears to have 

 reduced the effect ascribable to lime, whereas this effect 

 seems to have been augmented by fertilizers containing 

 little or no nitrogen." 



It may be said in general that lime as a soil amendment is 

 more likely to be beneficial on heavy clay soil, in humid 

 regions, where aeration is poor and the products of organic 

 decomposition are very likely to be toxic to plants. In 

 regions of low rainfall or sandy soils, lime is not so likely 

 to be required as a soil amendment. 



There are various chemical tests for determining the 

 probable lime requirement of a soil, but the most reliable 



