SOILS 49 



vegetables are grown successfully upon the heavier types 

 of soils. In the forcing of vegetables sand, and pre- 

 sumably fairly coarse sand, is more important than in 

 trucking or market gardening. The air spaces between 

 the particles are much larger in coarse-grained soils than 

 in the fine silts and clays, and for that reason such soils 

 are not so solid and compact. As explained by the fol- 

 lowing statements, the open, porous character of sandy 

 soils makes them peculiarly well adapted to the culture 

 of greenhouse vegetables. 



(1) Tillage is less difficult and less expensive than in 

 heavy soils. This factor is important in general farming, 

 but vastly more important in the handling of greenhouse 

 soils, since so much of the work, must be done by hand. 

 When plows and harrows can be used under glass, texture 

 from the tillage standpoint is not so important. 



(2) Sandy soils are well aerated, and this condition 

 accelerates chemical activity. In other words, oxidation 

 is more rapid in sandy soils, fertilizers act more quickly 

 and stable manures decompose and become available 

 sooner than in heavy soils. 



(3) Sandy soils are valued for trucking and market 

 gardening because they are light and warm, and crops 

 mature earlier in them than in heavy soils. The same 

 influence exists in the greenhouse, though to a less extent, 

 because moisture and temperature conditions are arti- 

 ficially controlled. In greenhouse management, time of 

 maturity is determined mainly by the date of planting; 

 nevertheless, sandy soils are favorable to rapid growth 

 and quick maturity. 



(4) It is important for greenhouse soils to dry quickly 

 on top after watering, because an excessive amount of 

 moisture at the surface is conducive to plant diseases. 

 This is especially true in lettuce culture. Surface 

 evaporation is most rapid in the coarse sands and slowest 

 in the fine silts and clays. 



