100 One Thousand Questions in Agriculture 



ductive. In such land as you describe no irrigation whatever would 

 be desirable except in years of short rainfall, and such land, if 

 properly cultivated, would always furnish moisture enough by capillary 

 action to support the growth of the plant. 



Less Water and More Heat. 



What chemicals should I put into the soil to insure a good crop of 

 vegetables, such as tomatoes, string beans, or other over-ground pro- 

 ducers? Last year my tomatoes and string beans grew plentifully, but 

 never produced any tomatoes or beans, yet turnips and parsnips were all 

 right. 



Vegetables which behave like your tomatoes and string beans, 

 making too much growth and not enough fruit, do not need fertiliza- 

 tion. The land is perhaps too rich already, or you may have used 

 too much water. Use less water so that the plants will make a more 

 moderate growth, and they will be fruitful if the season is warm 

 enough in the later part of summer. This, of course, would be one 

 of the drawbacks to growing tomatoes and beans in San Francisco. 

 Turnips and parsnips do well with less heat. You may have to 

 modify the San Francisco summer climate by wind screens or glass 

 covers. 



Continuous Cropping With the Same Plant. 



What would happen on the crops of cucumbers, tomatoes and egg- 

 plants, etc, planted -on the same place continuously? 



There would be in time a decadence of crop from soil exhaustion, 

 but that you could prevent by fertilization. The greatest danger from 

 continuously growing these vegetables on the same land is the mul- 

 tiplication of bacteria which injuriously afifect them, in the soil. The 

 plants which you mention are all subject to "wilt" diseases from this 

 cause, therefore, they should have new ground. If you have to use 

 the same garden ground continuously, the plants which you mention 

 should be rotated with root crops or with other kinds of vegetables, 

 so as to frequently change plants and soil within the general area 

 which has to be used for them. 



Big Worms on Tomatoes. 



/ have a nice patch of tomatoes in my garden, and only recently I 

 notice large green worms on them ivith one large brozvn horn on their 

 head. They strip the leaves off. They look to me like a tobacco zvorm. 



They are tobacco worms; that is, they are the larvae of hawk 

 moths, some of which take tobacco, tomatoes, grapevines and many 

 other plants, including some of the native weeds of your valley. 

 Pick them ofif and crush them, or give them a little snip with the 

 scissors if you do not like to handle them. They are so large and 

 easily found that such treatment is easily applied, as in "worming 

 tobacco." 



