22 SOILS AND FERTILIZERS 



might be true under special conditions. For example, 

 a sandy soil of good fertility in which the bottom water 

 is only a few feet from the surface, may produce larger 

 grain crops than a clay soil in which the bottom water 

 is at a greater depth. In judging the character of a 

 soil, the special conditions must always be taken into 

 consideration. In discussing the following soil types, a 

 normal supply of plant food and an average rainfall 

 are assumed in all cases. 11 



12. Potato and Early Truck Soils. The better types 

 of potato soils are those which contain about 60 per 

 cent of medium and fine sand, 30 per cent of silt, and 

 about 5 per cent of clay. Soils of this nature when 

 supplied with 3 per cent of organic matter will contain 

 from 10 to 20 per cent of water. The best conditions 

 for crop growth exist when the soil contains about 18 

 per cent of water. In a sandy soil, vegetation may 

 reduce the water to a much lower point than in a clay 

 soil, because the sandy soil gives up its water so readily 

 to growing crops and consequently a larger amount is 

 available, while on a heavy clay, crops show the want of 

 water when the soil contains from 10 to 12 per cent, 

 for the clay holds the water so tenaciously. When 

 potatoes are grown on soils where there is an abnormal 

 amount of water the crop is slow in maturing. For 

 early truck purposes in northern latitudes, sandy loam 

 soils are the most suitable because they warm up so 

 readily, and the absence of an abnormal amount of 



