242 CALIFORNIA VEGETABLES 



and that planting on the interior plains or in other parts of the 

 state where there is high heat and drought, or the soil becomes dry 

 even with moderate heat, planting must be undertaken early enough 

 to allow a large part of the development of the plant before such 

 stress comes. Local failures with potatoes may, therefore, be often 

 attributed to neglect of planting as soon as moisture and tempera- 

 ture conditions favor growth in each locality. 



Soils. Light, rich loams are best for potatoes as they favor 

 root extension and expansion of tubers and they are retentive 

 enough to hold the moderate amount of moisture which ministers 

 to the highest quality. Very near the coast well-cultivated, light 

 uplands receive atmospheric moisture enough to sustain the deep 

 verdure of the potato fields, while the pastures are sere and yellow. 

 Summer growth on interior plains and foothill slopes and mountain 

 plateaus is sustained by less irrigation than many other crops re- 

 quire, and winter growth, whenever feasible, is best on light, free 

 soils. The sediment and peat of the river lands are also, in their 

 season, light and warm. But the potato insists upon adequate 

 moisture, though its claim is moderate. It cannot give satisfaction 

 unless its moisture requirements are met. 



Heavy soils in garden culture can be greatly improved as de- 

 scribed in Chapter IV. Early and deep working of the soil and the 

 plowing in of rotten straw and compost and thorough mixture of 

 these materials through the soil will have marked effect, but heavy 

 land potatoes seldom have the beauty and flavor of the product of 

 the light, rich loams. 



Fertilising. Stable manure may be freely used if applied a 

 few months before planting and worked into the soil when moist 

 enough to promote decomposition. Ten or twelve tons to the acre 

 have been used to advantage. This may be followed by commer- 

 cial fertilizers just before planting. In the case of the record crop 

 in El Dorado county, previously mentioned, twelve tons of stable 

 manure per acre were spread and plowed in in December. In May 

 the winter growth of green stuff was plowed in and then a ton per 

 acre of commercial fertilizer, analyzing five per cent nitrogen, seven 

 per cent phosphoric acid and eight per cent potash, was disked in 

 and the crop planted. 



Culture. Deep working of the soil is essential in preparation 

 for potatoes as has already been urged for beets and other root 

 crops. The soil must be made mellow to a good depth and kept 

 mellow by subsequent cultivation. 



Certified Seed Potatoes. Assurance of good quality and free- 

 dom from disease in seed potatoes can now be had in California by 

 discriminating planters. The state legislature of 1914-15 passed a 

 law known as the California Certified Seed Potato Act, which es- 

 tablishes a standard for good seed potatoes. The administration of 

 this law is in the hands of the State Horticultural Commission at 

 Sacramento, from whom details may be obtained on application. 



