86 MISC. PUBLICATION 43 4, U. S. DEPARTMENT OF AGRICULTURE 



judge the proper depth, whereas if he is standing he may go too deep 

 and break off the sprout, or uncover too little and leave the seedling to 

 emerge through an excessive soil covering, in many cases causing con- 

 siderable loss. 



The crusting of surface soil over the seed following rain or irrigation 

 frequently presents a problem, especially in cases where the seed rows 

 are not ridged or where germination is prolonged following removal of 

 the ridges. As a solution, the Forest Service has devised a simple 

 implement for pulverizing crusts, called the rotary crust breaker 

 (fig. 27). This consists of a wooden cylinder enclosed in light-gage 



sheet metal and set 

 with nails. The nails, 

 punching a large num- 

 ber of holes in the soil, 

 effectively pulverize 

 the crust without dam- 

 age to the germinating 

 seedlings. A series of 

 spring-steel prongs 

 meshing with the nails 

 and pressing against 

 the roller serve to clear 

 the implement at all 

 times. The 2-wheel 

 push plow for carrying 

 the roller is preferred 

 to handles attached 

 to the axis of the 

 cylinder, since it per- 

 mits readier adjust- 

 ment of pressure to 

 meet the varying hard- 

 ness of the crust. It 

 also makes it easier to 

 pass over any portions 

 of the rows where the 

 seedlings may already have emerged to a satisfactory stand. Use of 

 the crust breaker provides all the cultivation necessary during germi- 

 nation to aerate the soil, speed up germination, and possibly guard 

 against damping off. 



If the nursery soil is quite dry, it should be irrigated before rather 

 than after seed sowing, in order to store up moisture in the soil for the 

 germination period. Irrigation will ordinarily not be necessary during 

 the germinating period if sufficient soil moisture is available at the time 

 the seed is sown, if proper cultural practices to conserve this moisture 

 are followed, and provided prescribed practices are followed with 

 respect to seed treatments to hasten germination. With overhead 

 sprinklers the problem is simplified, but in heavy soils crusting and 

 baking will occur following application of water. Furrow irrigation 

 presents a greater problem, since an average of 2 to 3 inches is usually 

 the minimum that can effectively be applied under this system in the 

 best type of nursery soils. It is desirable, therefore, to follow prac- 

 tices that will insure successful germination of the seed without 

 irrigation, especially where furrow irrigation is practiced later on. 



Figure 



27. — Rotary crust breaker for pulverizing 

 crusted soil over seed rows. 



