Soils and Soil Management 65 



a crop were grown every year on all the land, the yield 

 would not average ten bushels per acre. 



98. How Plants Dry the Soil. Do plants take moisture 

 from the soil faster than ordinary evaporation? To get 

 an answer to this question, fill four tomato cans with a 

 good garden loam. In one plant nothing; in another, 

 forty or fifty grains of oats; in another, five or six grains 

 of corn. Put an elder stem or hollow cane on the side 

 of each so that the plants can be watered from the 

 bottom. If we put water on the surface, a crust will 

 form that will cause the water to evaporate much faster. 

 (Do any of our experiments justify this statement?) 

 Pour just enough water down the tube to make the 

 soil reasonably moist, but not too wet. Set in a warm 

 place, and, when the seedlings are half an inch high, 

 weigh the cans and determine the loss of moisture in 

 the usual way. Keep the cans in a place where the 

 plants can get a good light, but not where the sun 

 would heat the earth too much. Sum up your results 

 at the end of the first week, and answer the questions 

 given above. Likewise, at the end of the second week. 



99. Absorptive Power of Soils. Soils have the power 

 of absorbing many substances, particularly some that 

 are valuable plant foods. The soil is a great purifier of 

 water. Prepare two lamp chimneys as described in ^] 95b, 

 and fill with good field or garden soil. Into one pour 

 several ounces of water made deep blue with laundry 

 blueing. Note the color of the water when it comes 

 through the cloth below. Into the second chimney pour 

 foul water made by leaching compost. Use as before. 



Wood ashes contain the salts left from the plant 

 when the air-derived substances have been driven off 

 by burning. It represents the valuable salts absorbed 



