PREPARATION OF SOILS FOR CROPS 257 



bacterial diseases, as grain smuts are held in check. 

 Low forms of plants, as fungi, also develop in soils 

 when conditions are favorable, and they take an im- 

 portant part in changing the character of the soil ; 

 their action may be either beneficial or injurious de- 

 pending upon the condition of the soil. Some of the 

 organisms which are propagated in the soil cause bac- 

 terial diseases of dairy and other farm products. There 

 is a very close relationship between soil sanitation, 

 crop diseases, and the quality of agricultural products. 



343. Influence of Crowding Plants in the Seed 

 Bed. The number of plants which a seed bed should 

 produce is dependent mainly upon the supply of water 

 and plant food. By means of thick or thin seeding 

 the general character of crops may be influenced 

 within definite limits. Either an excessive or a scant 

 amount of seed gives poor results. If over crowded 

 plants fail to develop normally it is either for want of 

 plant food or water or because of lack of room for de- 

 velopment. Experiments have shown that excessive 

 amounts of seed wheat, as more than 100 pounds per 

 acre of spring wheat, do not give good results. Each 

 crop has its limits beyond which it is not desirable to 

 crowd the plants in the seed bed. When there is ex- 

 cessive crowding, unhygienic conditions prevail and 

 the lack of air, sunlight and good ventilation encourage 

 bacterial diseases, while on the other hand too few 

 plants in the seed bed favor the growth of weeds and 

 an abnormal development of the crop. In the seeding 

 of grains and other farm crops, the amount of seed to 



