SOIL PREPARATION 81 



material. Where the soil is fairly well supplied with humus the 

 coarser part should be taken off and removed from the houses, 

 and the finer portion worked into the soil. 



"We are not prepared to say what effect the use of summer 

 mulch may have on the diseases affecting lettuce, except that the 

 station greenhouses have been very free from all diseases of lettuce 

 since we have been using this method of treating the soil. The 

 lettuce in the Toledo house has also been practically exempt from these 

 diseases during the two years they have been mulching. In no case 

 where the mulch has been used have we observed an increase in the 

 number of diseased plants over an equal area not mulched. These 

 facts, taken together with results secured by Stone and reported in 

 this circular, would lead us to expect beneficial rather than detri- 

 mental results from the proper use of summer mulch, in so far as 

 it affects the disease of lettuce." 



The Ohio station later compared manure mulch with 

 straw mulch. The details of the experiment are pub- 

 lished on pages 85 and 86 of the official proceedings of the 

 Vegetable Growers' Association of America for 1909, 

 1910 and 1911. The yields varied little at first, but the 

 fertility under the straw mulch became depleted quite 

 rapidly, as shown by the following report of 28 tomato 

 plants on an area of 120 square feet : 



PLOT 1 MANURE MULCH 



Total 881 279 11 



PLOT 2 STRAW MULCH 



Magnus 234 63 6 



Stone 234 75 11 



Beauty _ 254 76 12 



Total 722 215 13 



The results with lettuce were not so marked. There 





