146 AGRICULTURE ON THE PACIFIC SLOPE 



with sulphuric acid; the same are also made from rock phos- 

 phates. 



Liming. There should always be plenty of lime in 

 soils, because most crops grow best in land having from 

 1 to 4 per cent of lime. We can know that there is 

 lime enough when clovers or other legumes grow on 

 the land. When^ mainly rough grasses and sedges 

 grow, the soil itselL is sour, and should have lime put 

 on it. 1 For this we can use air-slaked lime^or else 

 marl, a soft, limy rock often found in California, and 

 in the coast ranges of Oregon and Washington, East 

 of the Sierra Nevada and Cascade Mountains, in Oregon 

 and Washington, southern Idaho, Montana, and from 

 Nevada to Wyoming and south to New Mexico and 

 Arizona, almost all soils have plenty of lime, except 

 sometimes in swampy places along the rivers and in 

 the high mountains. We can tell that there is plenty 

 of lime in soils when they have many legumes (plants 

 with flowers like the pea, such as lupins, loco weed, 

 clovers); also when there are plenty ^pf wiM^roses^ as 

 on the plains of Washington and Montana, where rose 

 land is known to be the most productive. Such lands 

 do not need liming. 



1 When soils are sour they make red spots on moist, blue litmus 

 paper put on the wetted soil. When red litmus paper is turned blue 

 after half an hour, it shows that enough lime is in the soil. If it is 

 turned blue at once, it shows that there is black alkali, and plenty 

 of it. 



