82 Diseases of Truck Crops 



and acid phosphate when used continuously will 

 leave the soil in a very acid condition. On the other 

 hand, nitrate of soda, carbonate of potash, and 

 Thomas phosphate tend to make the soil alkaline. 



Another important cause of malnutrition is the 

 exhaustion of humus. This is a natural result where 

 commercial fertilizers are used at the expense of 

 any form of organic manure. 



Methods of Controlling Malnutrition. From what 

 has already been said, the trucker is the loser if he 

 uses his fertilizer injudiciously. Not only is malnu- 

 trition favored by such a course, but the yields, too, 

 are considerably reduced. For instance, with cab- 

 bage, larger yields are obtained when iooo pounds 

 of commercial fertilizers are used than from any 

 higher application. Liming to neutralize the soil 

 acidity will help control malnutrition. To overcome 

 the humus deficiency of a soil the application of 

 stable or green manure is recommended. The 

 amount of manure to use will vary with the crop. 

 The important thing to guard against is the exces- 

 sive use of organic matter. For green manure, 

 the iron cowpea is recommended. This variety is 

 resistant to wilt, and fairly so to root knot. The 

 best time to plow under green manure is generally 

 in October when the plants approach maturity. 



BLOSSOM DROP 



This is another trouble which may be termed 

 physiological, and the cause of which cannot be 



