INCREASE OF CROPS BY USE OF FERTILIZERS n 



constant conditions till they had ripened this difference 

 might finally disappear, but in crop production it is not 

 possible much to delay the harvest owing to the fear of 

 damage by autumn frosts, so that the retardation is of great 

 practical importance. Seed crops like barley that are cut 

 dead ripe are not supplied with much nitrate, but oats, which 

 are cut before being quite ripe, can receive larger quantities. 

 All cereal crops, however, produce too much straw if the 

 nitrate supply is excessive, and the straw does not commonly 

 stand up well, but is beaten down or " lodged " by wind and 

 rain. Swede and potato crops also produce more leaf, but 

 not proportionately more root or tuber, as the nitrogen supply 

 increases ; no doubt the increased root would follow, but the 

 whole process is sooner or later stopped by the advancing 

 season the increased root does in fact follow in the case of 

 the late-growing mangold. Tomatoes, again, produce too 

 much leaf and too little fruit if they receive excess of nitrate. 

 On the other hand, crops grown solely for the sake of their 

 leaves are wholly improved by increased nitrate supply : 

 growers of cabbages have learned that they can not only 

 improve the size of their crops by judicious applications of 

 nitrates, but they can also impart the tenderness and bright 

 green colour desired by purchasers. Unfortunately the 

 softness of the tissues prevents the cabbages standing the 

 rough handling of the market. ' ' Some of the results obtained 

 at Rothamsted in studying the stimulative effect of nitrogen, 

 are exhibited in a very brief form in Table i. 



TABLE i. 



ROTHAMSTED, BROADBALK FIELD, WHEAT. 

 Average of 61 years. 



