748 



Horticulture in Penzance. [Nov.^ 



dung heap layers of sea sand are introduced at intervals, and 

 the top of the heap is also covered with sand and soil. The 

 sea sand in the Penzance area contains a high percentage of 

 lime derived from shells and other calcareous matter, and as 

 much as 5 per cent, is quite common. This sand aids in the 

 decomposition of the seaweed and fish offal, and will ultimately 

 benefit the land which is naturally deficient in lime; how far 

 it tends to liberate feeding material from the manure into the 

 air does not seem to have been definitely ascertained. This 

 heterogeneous mass is applied to the soil in winter or early 

 spring at the rate of 80-120 loads and upwards per acre. Assum- 

 ing that a load is only 13 cwt. owing to the inaccessibility of 

 many of the small fields, the quantity represents a very heavy 

 dressing. In addition to this, chemicals are applied in appar- 

 ently excessive quantities. Nitrate of soda and sulphate of 

 ammonia are applied as top dressings, usually in equal propor- 

 tions, from 10-14 cwt. per acre being used. In some cases 

 sulphate of ammonia alone is applied at the rate of 8-10 cwt. 

 per acre. Superphosphate is also applied, seldom less than 

 10 cwt. per acre. It is generally assumed that sufficient potash 

 is applied in the dressing of seaweed and dung, but there are 

 no experimental data to prove this. Some of the growers con- 

 sider that an adequate return is not obtained for this heavy 

 outlay on chemicals, and several have been experimenting by 

 leaving a portion undressed. In the Isles of Scilly very little 

 nitrogenous fertiliser is used, although the soils are very similar 

 to those of the mainland. Seaweed, fish offal, &c., are princi- 

 pally used, but when a heavy dressing of " green " seaweed 

 is applied very poor results are obtained. The crop is consider- 

 ably retarded and stunted by the undecomposed seaweed and 

 does not wholly recover during the season. This points to the 

 necessity of having the material decomposed and mellowed hy 

 the atmosphere before application to the soil. No spraying is 

 done, even in a bad year. The usual course is to lift the crop 

 as speedily as possible when disease appears on the foliage and 

 before the spores have had time to fall and enter the tubers. 



Potato Diseases. — Considerable patches were affected with 

 black leg {Bacillus atrosepticiis), which w^as most apparent in 

 May Queen and Duke of York. Sharpe's Express appeared to 

 be very little affected. 



Mosaic disease was very prevalent, principally in May Queen 

 and Duke of York. Growers are of the opinion that these two 

 varieties are becoming " played out " in the Penzance area> 



