10 Nov., 1917.] Composition of the Potato Plant. 655 



crop removes large quaiililies of plant t'cjdd from the soil per medium 

 of the eolleetion and reiiioval of the tuhers. 



As previously stated, tiic absolute dry weight of tuliers in the above 

 crop would be 2 tons. 



Calculating from Tabic VIll. we tiud Si lbs. of nitrogen, ul lbs. of 

 phosphoric acid, and 144 lbs. of potash removed per acre in the form 

 of tubers. 



The 81 lbs. of nitrogen is equivalent to a 4-cwt. dressing of ammo- 

 nium sulphate. The 31 lbs. of phosphoric acid would be contained in 

 1| cwt. of su|)erphosphate, whilst 144 lbs. of potash would be supplied 

 by approximately 3 cwt. of potassium sulphate. 



These figures represent the actual loss to the soil, and are given with 

 the object of impressing the potato grower ^vith the requirement.s of the 

 crop, and the necessity of manuring to make good actual loss from the 

 soil by cropping. 



Summary. 



1. The three essential plant foods, viz., nitrogen, potash, and phos- 

 phoric, once absorbed by the potato plant, are utilized, as no migration 

 from the plant to the soil takes place. 



2. The critical period of growth is the first six or eight weeks. 



3. The greater part of ]3hosphoric acid enters the plant in the early 

 stages of growth, concentrating in the haulm, and then playing an im- 

 portant part by migrating to the stolons for tuber formation. 



4. Potash and nitrogen play a consistently even part right through 

 the growing period. 



5. Practically the whole of the root development takes place during 

 the first two months. 



6. Haulm development is most active during the first two months. 



7. The amounts of lime and magnesia assimilated by the jjotato 

 plant seem to bear a definite relation. 



8. The very young potato tuber is richer in phosphoric acid than 

 the .semi or mature tuber. (Table VIII.) 



9. Phosphoric ■acid and nitrogen present in the seed set are largely 

 utilized in sprout formation. Potash apparently is not directly utilized. 

 (Table V.) 



10. The results of the experiment taken collectively show that 

 manures must be available during the first month. 



11. Potatoes can be grown on poor sandy soils, provided that avail- 

 able plant foods in the form of artificial fertilizers, in conjunction with 

 farmyard manure, are judiciously applied, the quantity and quality of 

 the produce being favorably comparable with the best potato soils. 



12'. The value of the dried haulms and roots may be compared to 

 famiyard manure in favour of the dried haulms, 1 ton 6f which would 

 supply three times as much nitrogen and phosphoric acid, and approxi- 

 mately ten times the amotmt of potash as would be contained in 1 ton of 

 farmyard manure. 



13. The composition of the potato tuber, under experimental con- 

 ditions, may be influenced in so far as the ])hosphoric acid content if 

 concerned. 



14. During the growing period the potato plant utilizes phosphoric 

 acid, nitrogen, and potash, in the proportion of 1, 4, 6, i.e., 1 part of 

 phosphoric acid to 4 parts nitrogen to 6 parts potash. 



