52 



natural drainage canals ; after the crop is removed, the soil is left 

 naked during the winter and the heavy rains wash and erode the 

 surface and remove some of the best plant-food. After a few years 

 of such treatment, the farmer wonders why the soil will not pro- 

 duce as liberally as it formerly did. 



Experiment No. 1. — The fact that there is humus or vegetable 

 mold in certain soils can be shown by burning. Weigh a potful of 

 hard soil and a potful of lowlands soil or muck, after each has been 

 thoroughly dried. Then put the pots on the coals in a coal stove. 

 After the soil is thoroughly burned, weigh again. Some of the dif- 

 ference in weight may be due to loss of moisture, but if the samples 

 were well dried in the beginning, most of the loss will be due to the 

 burning of the humus. 



Conditions which Affect Fertility. 



■There are certain conditions which affect soil fertility and of these 

 the most important are : 

 Texture. 



Moisture-content. 

 Plant-food. 

 Temperature. 



Texture and its Relation to Fertility. 



By texture is meant the physical condition of the soil. Upon 

 good texture, more than upon any other one tiling, depends the pro- 

 ductivity of the soil. When the texture is right the soil is fine, 

 loose and friable ; the i-oots are able to push through the soil and the 

 feeding area is enlarged. Each individual pai'ticle is free to give up 

 a portion of its plant-food or its film of moisture. The conditions 

 wliich are found in the woods' soil are almost ideal. 



Experiment No. 2. — The importance of good texture can be well 



shown in the class-room. Pots should be filled with a soil which is 



lumpy and cloddy and other pots with the same kind of material 



after it has been made fine and mellow. Seeds should then be 



planted in the different pots and a careful study made of the length 



of time required for germination and of the health and vigor of the 



plants 



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