244 Bacteria in Relation to Country Life 



of water. This means that three tons of hay will cause 

 the loss from the soil of moisture equivalent to nine or 

 ten inches of rainfall. Furthermore, this will not repre- 

 sent the entire loss, since moisture is also evaporated 

 from the soil directly, or is lost by percolating downward 

 into the subsoil. 



Because of the drying effect of the main crop, the 

 moisture content of the soil is frequently reduced to 

 such an extent as to prevent the germination of the 

 green-manure crop. But should the latter germinate 

 properly and grow well, its drying effect on the soil may 

 result in serious injury to the succeeding crop. It is a 

 fact familiar to most farmers that green-manure crops, 

 especially when they have matured too far, may, at 

 times, remain undecomposed in the soil. There arises, 

 then, a two-fold injury to the succeeding crop, the 

 partial exhaustion of the soil-moisture and, therefore, 

 its insufficient supply, and the far-reaching destruction 

 of the soil bacteria. 



As the soil dries out, the number of these latter 

 decreases rapidly and the natural bacterial balance is 

 destroyed. The decomposition of the green-manuring 

 crop is then temporarily stopped. When the water 

 content of the soil is again increased by rainfall, the 

 decomposition does not proceed in the same way as it 

 would have proceeded had the soil remained sufficiently 

 moist. It is best, therefore, not to seed a green-manuring 

 crop in a dry soil, nor allow a green-manure to become 

 too mature before it is turned under. When the growth 

 is very bulky, it is always better to harvest the crop 

 and to plow under the stubble alone. 



