CALIFORNIA ONION GROWING 219 



supply may be retained by cultivation, or for which irrigation is 

 available to counteract natural tendency to dryness, is necessary for 

 the full success of the onion as a mature crop. In the winter, if 

 rains are up to the average, very good growth of green onions can 

 be had on land which is too dry in summer to carry the bulb to full- 

 sized maturity. For satisfactory summer finishing of the crop, soils 

 which are prone to dry out must be avoided, unless irrigation is 

 available. How this matter is affected by methods of propagation 

 will appear presently. 



If the needed moisture can be afforded, onions can be well 

 grown on a variety of soils. Quite heavy adobe can be made to do, 

 but it will be at the cost of much thorough cultivation, producing 

 tilth which is difficult and expensive to attain on such soil. Every 

 addition of sand or silt to the adobe improves it in this respect, and 

 the ideal soil for the onion is one which is retentive enough under 

 cultivation to keep the plant roots from a touch of drought, and 

 friable enough to be easy in cultivation and easy also for the ex- 

 panding bulb to displace as it grows. The bulb should expand on 

 the ground surface, not under it, and it is very difficult to secure 

 this on a clay without baking of the surface, which dries the roots 

 and results in prematurity and small size in the bulb. On the other 

 hand, sandy soil is usable only at a cost of frequent irrigation, for 

 it also loses surface moisture in spite of stirring. Besides suitable 

 mechanical condition of the soil, it is essential that it shall be rich 

 in plant food. Onions resent a poor soil. Fortunately California 

 has large areas of loam, of mixed peat and sediment, and of allu- 

 vial soils, which are so rich that many onion crops can be grown 

 without fertilizing, but in garden work the free use of manure is 

 the secret of quick, tender and large size, both in the green and 

 mature onion. But the use of fresh manure just before planting is 

 not desirable, and even well-rotted manure should be applied several 

 months in advance of planting, that it may become thoroughly in- 

 corporated with the soil. 



The great onion regions of the state are the lower stretches of 

 the rich coast valley, the moist river lands in the interior, and 

 the winter crop in the so-called "desert" lands of the Coachella and 

 Imperial valleys, where the crop is grown by irrigation. Other- 

 wise onions are grown largely by rainfall and natural seepage. Fine 

 onions are also grown on upland loams, wt'ch or without irrigation, 

 according to local climatic conditions. All these classes of lands 

 occur in large areas throughout the state. 



Propagation of the Onion. The onion is grown here, as else- 

 where, by three main lines of propagation: from seed sown in the 

 field, from transplanting seedlings and from sets. The last is by 

 far the least important in California, and the choice between the 

 other two depends upon the special end in view, as will appear in 

 the discussion of them. 



