252 THE SMALL GRAINS 



found to be more resistant on the whole than oats, and 

 maize more than either of these. 



269. The calcium-magnesium ratio. The results of 

 Kearney and Harter, showing the neutralizing effect of 

 calcium on the toxicity of magnesium salts, are in accord 

 with those of Loev (1903) and others, who found that the 

 best harvests of certain crops are obtained only when the 

 amount of lime in the soil is of at least a sufficient quan- 

 tity to bear a certain ratio to that of the magnesia. For 

 certain cereals, the amounts should be about equal, but 

 the magnesia should particularly not be in large excess. 

 Daikuhara (1905) was able to obtain a barley harvest from 

 50 per cent to 150 per cent greater by correcting the 

 lime-magnesium ratio so as to increase the amount of lime 

 considerably above that of the original soil. Miyake 

 (1913-14), in recent literature, has shown in experiments 

 with rice seedlings the antagonistic and neutralizing effects 

 of potassium, sodium, magnesium, and calcium salts upon 

 each other, the calcium being especially effective in neu- 

 tralizing the poisonous action of other salts. 



270. Soil temperature. Much of the good effect 

 resulting from favorable soil conditions is indicated in the 

 rise of the soil temperature. This is a factor of consider- 

 able importance in early spring. At such a time a " warm 

 soil " is of great advantage in giving the cereal crop an 

 early start, whether it be spring sown or a winter variety 

 renewing its growth. Better aeration permits a higher 

 temperature in sandy soils. As a high soil temperature 

 hastens growth, we have here, probably, a good basis of 

 fact for the common idea that coarse or sandy soils are 

 adapted for early crops. The flocculating effect of lime 

 in favoring aeration of clay soils is of importance in this 

 connection. 



