14 GRASSES AND HOW TO GROW THEM. 



germination and unchecked growth after the plants have 

 started. It is secured under dry conditions by plough- 

 ing the soil or disking it some time previous to the sow- 

 ing of the seed and then by harrowing it at intervals 

 to form and preserve what may be termed a dust mulch 

 to prevent the escape of subterranean moisture through 

 capillary action. This power to retain moisture also 

 increases with the increase in the proportion of humus, 

 that is of decaying or decayed vegetable matter in the 

 soil. The abundant presence of this element is not so 

 necessary to the successful growth of grasses as to that 

 of the small grains, since one object in growing grasses 

 in the rotation is to increase the humus in the soil. 

 Nevertheless, up to a certain limit, the presence of 

 humus is quite helpful to the growth of these also. 



Firmness in the soil is secured by having a consider- 

 able interval between the ploughing of the soil or the 

 first disking of the same, and the sowing of the seed. 

 It is further aided by harrowing, rolling and rainfall. 

 It is beneficial, since it tends to exclude an excess of air 

 in the soil near the surface, and since it also conduces 

 to resistance to the influences that tend to promote the 

 escape of moisture by surface evaporation. It also ren- 

 ders soils which are liable to heave less susceptible to 

 the action of frost. This condition, therefore, is of 

 much consequence with such soils when grass seeds are 

 sown upon them in the autumn. With light spongy 

 soils, a firm condition is even more important in the 

 spring, and especially under conditions when moisture 

 may be more or less lacking. An excess of firmness 

 in certain heavy soils may be induced by excessive rain- 



