CONSTRUCTION NOTES 289 



looser, warmer soils they may be deeper and farther apart since their influ- 

 ence extends farther in light soil. Ordinary agricultural tile laid as described 

 in pages 238 to 253 (Drainage) will generally serve best for lawn drainage. 

 Care should be taken to get this drainage laid and the trenches back-filled 

 and well settled before any attempt to sow grass seed is made or else the 

 settling may occur after the grass is up and leave disfiguring grooves across 

 the lawn. 



Lime. The second fundamental consideration in the making of a lawn 

 is the condition of the top 18 to 24 inches of soil, as regards its supply of 

 lime. This applies to the subsoil just as much as to the topsoil. In places 

 where the topsoil is sweet or even alkaline, the subsoil may be acid and the 

 effect of the acidity may not be very apparent until a period of extremely 

 dry weather comes along. There is a theory that in such a dry spell the 

 acid soil moisture affects grass roots very severely and even kills them. 

 Blue grass and Bermuda grass and clover will not succeed unless lime is 

 present, while many other grasses prefer a sweet or neutral soil. The use 

 of lime is also justified by its power to stimulate bacterial activity in the 

 soil and especially those bacteria which carry on the process known as 

 nitrification or the making available of the nitrogen in the soil humus. Even 

 though the bent grasses and the fescue grasses are not much influenced 

 either way by the presence of lime itself in the soil, they respond to the 

 nitrogen released from the soil humus and are thus indirectly benefited. 



Since a lawn is laid down permanently, as a rule, enough lime should 

 be added at the start to ensure a supply for a long time. As much as eight 

 to ten tons per acre of ground limestone, or its equivalent, may be used if 

 the soil is found to be at all acid, and this should be thoroughly incorporated 

 throughout the top layer of soil. 



Humus. The third factor which is of vital importance in lawn making 

 is the securing, in the soil, of a plentiful supply of humus. This may be 

 secured, when deficient, by plowing under a cover crop or by applying stable 

 manure. Cover crops can only be grown at certain seasons of the year, 

 while manure can be applied at any time. The vetches, clovers, and rye 

 grasses are all valuable green manures. When these green crops are plowed 

 under care should be taken not to allow them to bunch up in front of the 

 plow coulter or plowshare so that they are turned under in large masses 

 which ultimately decay and cause depressions all over the lawn. When a 

 true and permanent lawn surface is a very important desideratum, it is 

 sometimes worth while to cut heavy cover crops and put them through a 

 hay or ensilage cutter, then spread them upon the lawn and plow them 

 under evenly. 



Stable manure should preferably be well rotted before it -is applied to 



