THE FOREST NURSERY 101 



determined by conditions. Sub-irrigation carrying water 

 in porous or perforated pipes eight or ten inches below the 

 surface has succeeded well in greenhouses and possibly 

 might be adopted in forest nurseries. Experiments in that 

 direction should be undertaken, for that system puts the 

 water just where needed and does not cause cracking of the 

 surface. 



No matter how carefully watering with a hose or a pot 

 may be done, there is invariably formed a muddy, compact 

 surface of the soil, and this is followed by crusting and 

 cracking of the surface as soon as the sun shines upon it 

 for a few hours, or a strong wind blows over it. After every 

 such occurrence, and also after every heavy rainfall, the 

 crust which forms should, where the system of sowing will 

 permit, be broken and the surface pulverized as soon as 

 the ground is dry enough to work. By doing this less 

 water will be required, for however strange it may appear, 

 fining and pulverizing the surface soil actually retards 

 evaporation. This fact is well understood by those who 

 have tried it. It is so thoroughly known by farmers over a 

 vast area in the so-called semi-arid sections of the Great 

 West, where there is but slight rainfall, that profitable 

 crops are being grown though not a drop of water comes 

 to the ground after the seeds are sown success being 

 achieved by ploughing deep just before the rainy season, 

 and this followed by a frequent stirring of the surface of 

 the soil where the character of the crop will permit it. A 

 blanket of dust, however dry it may be, prevents rapid 

 evaporation. 



Stirring and making fine the surface of the soil not only 

 lessens evaporation, but it admits air to the roots, which is 

 necessary, and, in addition, it keeps down weeds and less- 

 ens the labor of removing them by hand. Clean cultiva- 

 tion is as important in the forest nursery as elsewhere, and 

 it cannot be begun too early ; and that means stirring 

 the soil whenever it can be safely done. Stirring the soil to 

 a slight depth, but not too close to the plants, can be pro- 



