64 VEGETABLE GARDENING 



be observed (Va. Truck Expt. Sta. Bui. i, p. 5): (i) 

 "The plants stop growing when they should be making 

 their most rapid development. In many cases they slowly 

 weaken and die, while in others growth is resumed later 

 in the season after rains have occurred. (2) There is a 

 change of leaf color to a lighter green, especially in the 

 spaces between the veins, which turn yellowish-green or 

 even brown. In cabbage the margins of the leaves are 

 frequently of a uniform yellow color. (3) The roots of 

 the affected plants are poorly developed. Many of the 

 lateral feeders are killed back repeatedly, until the root 

 system becomes stubby. (4) No fungi or bacteria can 

 be connected with the disease. In most cases none is 

 present." 



In the Norfolk region 3,000 pounds of fertilizer to the 

 acre are often applied during the season's operations and 

 this amount is used year after year, resulting in a strongly 

 acid soil. The Virginia Truck Experiment Station states 

 also (Va. Truck Expt. Sta. Bui. i, p. 5) that "acid soils 

 are less favorable for the production of most truck crops 

 than neutral soils. A slight amount of acidity is not 

 ordinarily injurious, but examinations made at our re- 

 quest by the Bureau of Soils of samples from fields where 

 cabbage suffered from malnutrition, showed these soils 

 to be abnormally acid, so much so that 3,500 to 6,300 

 pounds of Hme would be required to neutralize an acre 

 to a depth of I foot. This condition is apparently the 

 result of many years of intensive trucking, involving 

 the use of repeated heavy applications of commercial fer- 

 tilizers made up in large part of chemicals which leave 

 the soil more acid. 



"Only a portion of the fertilizer applied is actually 

 taken up by the plants, the remainder being left in a dif- 

 ferent form, which will have an influence on the soil 

 reaction. For example, sulphate of ammonia, muriate 

 and sulphate of potash, and acid phosphate tend to leave 



