900 



Experiments in Potato Growing. 



[FEB., 



was taken to apply exactly the same amount of manure to 

 each experimental plot, and the artificial manures were mixed 

 and weighed up in bags before the planting season arrived, 

 so that when the soil was ready all the experimental crops 

 could be planted quickly, thus ensuring uniform conditions. 

 The weight of artificial manures applied varied slightly in 

 each year according to the quality of the fertilisers pur- 

 chased, but the constituents of the mixture were always the 

 same. The mixture applied in 1906 is shown below as being 

 typical of the manuring in other seasons. Nitrogen was 

 supplied in four forms, so as to extend its action, so far as 

 possible, over the growing season. Bone meal was used 

 chiefly with the object of producing a dry powdery manure 

 that would keep in good condition when stored prior to 

 sowing. The use of bone meal would cause a slight rever- 

 sion in the soluble phosphate of superphosphate, but in 

 practice this would not detract from the value of the manure. 

 The composition of the mixture is given below : — 



35 lb. of nitrate of soda 

 100 ,, sulphate of ammonia 

 75 ,, bone meal 

 50 ,, dissolved bones 

 340 „ superphosphate 

 155 sulphate of potash 



per acre. 



Manurial Experiments. — For five consecutive years 

 manurial tests were carried out in the County of Hertford- 

 shire in districts where for many years very heavy dressings, 

 30 tons or so per acre, of "London dung" have been used. 

 The object of these experiments was chiefly to see if smaller 

 dressings of dung, supplemented by a compound artificial 

 manure, would not give a more profitable crop. For four 

 seasons out of the five the results have been that a very 

 liberal dressing of manure has shown a direct financial loss. 

 The extra manures have not increased the crops sufficiently 

 to meet the cost of manuring. 



When potato growing was begun in this neighbourhood 

 the value of heavy dressings of " London dung " may have 

 been obvious, and growers having discovered that the prac- 

 tice paid well, assume that it does so now. But as fertility 

 accumulates in land, manures become less effective, and the 

 assumption may be a costly one. The potato crop certainly 

 pays for liberal treatment, but its capacity is not unlimited, 



