74 



Problems in Potato Growing. 



[may, 



The muriate being the cheaper manure, the advantage from 

 its use was considerable. In 1905, kainit, J-} cwts. per acre, 

 was tried against the two other potash manures, with the 

 same quantities of superphosphate and sulphate of ammonia, 

 and the total yield per acre was only 5 tons 2 cwts. 20 lb. In 

 all three cases artificial manures alone were used. 



A more complicated question is that of the most profitable 

 quantities and proportions of the three constituents of a complete 

 potato manure, with and without 10 tons of farm manure 

 respectively. A great number of published experiments bear 

 upon this subject, but so irregularly that no definite decisions 

 are to be derived from them. In this case, again, variations of 

 soil and differences in the condition of land in reference to 

 fertility in addition, would render uniformity hopeless. Still, 

 if carried out under a uniform plan, a large number of trials 

 would be instructive, taking superphosphate, sulphate of am- 

 monia and sulphate of potash as the complete mixture of artificial 

 manures. After all however, the best guidance for a grower to 

 obtain is to carry out the trial on his own land. My own ex- 

 perience points to 4 cwts. of superphosphate and 2 cwts. each 

 of the other two manures as the most profitable dressing when 

 no farmyard manure is used. In one field last season the 

 omission or halving of any one of the manures greatly reduced 

 the yield, and the addition of 50 per cent, of superphosphate also 

 diminished it. 



Lime. — Many growers will contend that lime should be added 

 to make a complete potato manure, but no precise experiments on 

 this point have come to my. notice, with the exception of one 

 in each of the fields referred to above, and this trial was unsatis- 

 factory, because the lime was placed in contact with the other 

 manures. In each field it appeared to reduce the yield ; but 

 this may have been in consequence of its action upon the sulphate 

 of ammonia. In Scotland it has recently been common to apply 

 about 6 cwts. of ground lime per acre just before the field is 

 cultivated for planting, and when so used it is incorporated with 

 the soil and slaked before it comes in contact with other manures. 

 When so applied on my crops at large, as it has been in two or 

 three years, it has appeared to do some good, judging from the 

 appearance of the haulm when part of a field has not had any 

 lime ; but the difference in yield was not obvious on inspection, 



