62 



SOIL CONDITIONS AND PLANT GRO WTff 



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. At the Cheshunt Experiment Station l the omission 

 of nitrogen compounds from the fertiliser mixture has caused 

 the yield of fruit to increase 1 1 per cent. With the variety 

 Comet the following quantities of fruit have been obtained : 



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 cabbage standing the rough handling of 

 the market. These qualitative differences are of great import- 

 ance in agriculture and horticulture. 



Three cases are illustrated in Table XVII. ; as the nitro- 

 gen supply is increased wheat shows increases in straw greater 

 than those in grain ; white turnips show increases in leaf 

 greater than those in root, but mangolds show substantially 

 the same increase both in leaf and root, because their growing 



1 Annual Reports for 1917 et seq. 



