9 Sept., 1907.] 



Potato Experimental Fields.. 



559 



the projjortion of marketable seed differs with varieties and this no doubi: 

 is influenced by the manures used, so that to make a definite statement 

 that any particular manure or combination of manures is the best for 

 potatoes is courting criticism. 



The following digest of all potato fields, disregarding varieties of 

 tubers sown and lo:-alitv, offers some jieneral information: — 



It will be noted that 2 cwt. per acre of superphosphate has produced 

 an increase of .6 tons (12 cwt.) per acre over the unmanured land. 

 Adding i cwt. sulphate of ammonia to the superphosphate further in- 

 creases the improved yield to i ton 4 cwt. per acre. The further addition 

 of I cwt. of potash sulphate to the superphosphate and sulphate of 

 ammonia shows an enhanced increase of i ton 8 cwt. per acre. To put 

 the matter on a commercial basis, a dressing of 2 cwt. superphosphate. 

 1 cwt. sulphate of ammonia and i cwt. potash sulphate costing approxi- 

 mately 37s. 6d. per acre has produced an extra yield of t ton 8 cwt. of 

 potatoes:, which at £^2 los. per ton would be worth ^3 los. over and 

 above what was produced from the unmanured land. Manuring therefore 

 pavs handsomely. The cost mav seem rather high, but if potatoes were 

 worth ^c^ per ton instead of ^2 los., the profit would have been double 

 for the same expenditure in manures. 



Attention might be drawn to the fact that farm manure alone has 

 produced an increased yield of .5 tons (10 cwt.) per acre, which mav be 

 taken as evidence of the virtue of this much neglected material. Had 

 the farm m.anure been supplemented by artificial fertilisers, the results 

 w^ould have probablv been much more prominent. 



The Field Branch recognises the value of these manuring trials with 

 potatoes, but advises caution in the use of excessive dressings, which might 

 stimulate a too abundant growth of tops to the detriment of the tubers. 

 It is perhaps superfluous to add that the cultivation of potato land must 

 alwavs regulate the action of the manures. 



