1018 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



on plots on which the lighter dressing of dung has been supplemented by 

 chemical fertilisers. 



The most economical, though not quite the largest, results appear to 

 have been obtained by the use of dressings including 2 cwt. of nitrate of 

 soda per acre. 



Potash has not, on the average, increased the crop, but in 1900 it 

 produced very decided results where no dung was used, as will presently 

 be seen. 



It also appears, as the result of our experiments, that Summer Lettuces 

 can be grown satisfactorily without the use of dung at all, though the 

 Lettuces do not attain to quite the same dimensions as those grown under 

 more liberal treatment. 



The following results summarise our experience of growing Summer 

 Lettuces with and without dung. It is necessary, however, in order to 

 make the results strictly comparative, to average the first four crops and 

 to consider the last one separately, for in 1900 the dressing used on the 

 undunged plots was more liberal than in the earlier years. 



SUMMER LETTUCES. 



Annual manuring per acre. 



50 loads (25 tons) London Dung . 

 25 loads (12- tons) London Dung 

 25 loads Dung, Phosphates, and 2 cwt. Nitrate 



of Soda 



25 loads Dung, Phosphates, and 4 cwt. Nitrate 



of Soda 



No Dung ; Phosphates (without Potash) and 



4 cwt. Nitrate of Soda .... 

 Ditto, ditto (with Potash) .... 

 No Dung ; Phosphates (without Potash) and 



8 cwt. Nitrate of Soda .... 

 Ditto, ditto (with Potash) .... 



Annual cost 

 of manure 

 per acre 



£ 

 10 



5 



6 15 0 



7 15 0 



Average weight per plant 



Four crops (dur- 

 ing 1896-1898) 



oz. 

 9-5 

 7-8 



103 



10-4 



9-0 

 93 



It will be seen that chemical dressings alone produced better results 

 than did the lighter dressing of dung ; and, although they did not give 

 quite such good results as heavy dressings of dung, the cost of the manure, 

 even on the most heavily dressed chemical plots, was only about half that 

 of the heavy dunging. Nevertheless, as the welfare of Summer Lettuces 

 depends largely upon a suitably moist ctndition of the soil soon after the 

 time of planting, the application of a moderate dressing of dung, in 

 addition to chemical fertilisers, seems desirable, in order to diminish the 

 dangers attendant upon possible dry weather. 



