56 



CROPS UNDER GLASS 



Mr. Zuck: I think with Grand Rapids lettuce we almost 

 always get three or very nearly three full crops, and then an 

 intercrop with the cucumbers or tomatoes. 



Question: How many seasons are you able to use that 

 soil? 



Mr. Zuck: We have had soil in there nine years this 

 spring. Advice seems to be that we change about once a year. 



Mr. Work : The florists change their soil practically every 

 year, or perhaps every two years. The vegetable men prac- 

 tically never change their soil. I know of some places where 

 soil has been used year after year and year after year with- 

 out change. I have been in greenhouses where it has been in 

 use twenty years. They maintain the fertility by large 

 amounts of manure, and when disease comes, they sterilize. 

 The summer mulch system Mr. Zuck mentions, in which they 

 put on a heavy coat of manure in the summer, letting it lie 

 there and keeping it moist for some weeks, then raking off 

 the very coarsest of it, seems to help materially in controlling 

 disease. 



Mr. Zuck: We always turn that manure under and then 

 sterilize. There are not manj^ places where they do not 

 sterilize now. 



Mr. Work : When the soil mulch idea was first suggested, 

 people thought maybe sterilization would not be necessary. 



Question: Do they ever lime? 



Mr. Zuck: We lime every summer. We add a couple of 

 tons of ground rock lime to an acre. 



Mr. Work : In contrast with this manure-sterilization-lime 

 method of maintaining fertility, we have the scheme of the 

 florist. They have to have some outdoor space that they can 

 use for soil purposes, and they build up the fertility of that 

 land by the use of cover crops, manure and tillage and get 

 that soil into nice shape, while the old they take out bodily. 

 They do not feel that the soil will give them results by steriliz- 

 ing. How about lime, Professor Beal? 



Professor Beal : They use lime when they pile up the soil. 



