244 



Journal of Agricultural Research 



Rape was also grown upon sand. The sand employed was obtained 

 from the Wausau Quartz Co., Wausau, Wis. It was an angular product, 

 designated as No. 2, which passed almost completely through a sieve of 

 40 meshes to the inch, but was half retained by a 6o-mesh sieve." It con- 

 tained small amounts of impurities, but no sulphates. Fifteen kgm. (33 

 pounds) of this sand were placed in the usual boxes with the following 

 fertilizer treatments: 



Boxes Nos. Gm. 



Tricalcium phosphate (Ca3(P04)2) 12. o 



Potassium chlorid (KCl) 4. 5 



Magnesium nitrate (Mg(N03)2) 2. 5 



Sodium nitrate (NaNOg) 8. o 



Calcium carbonate (CaCOj) 5. o 



Iron chlorid (FeClg) i. o 



3-4. Like I and 2+calcium sulphate (CaSO^) 12. o 



5-6. Like I and 2+sodium sulphate (Na2S04) 12. o 



7-8. Like I and 2+sodium sulphate (Na2S04) 6. o 



All of the salts, except sodium nitrate, were mixed with the sand 

 before planting, but this was applied to the growing plants in portions 

 from time to time. At 84 days of growth, when the plants gave the 

 usual signs of maturity, the crop was harvested. The yields of the 

 air-dried rape crops are given in Table VI. 



Table VI. 



-Average weights {in grams) of air-dried rape crops 



In these cultures the calcium sulphate was beneficial, but the sodium 

 sulphate depressed the yields as compared with the basal complete ferti- 

 lization. The data show this effect of the sodium sulphate least where 

 the smaller amount of salt was applied. This again seems to indicate 

 that the depressed effect was due, in part at least, to an excessive con- 

 centration of soluble salts. If such an effect were appreciable, one would 

 expect it to be more pronounced in the case of the sand than with soil 

 on account of the lower absorptive power of the former, and such was 

 the case. The calcium sulphate exerted a remarkable effect on the 

 development of the rape roots in these cultures. An objection might 

 possibly be raised that the beneficial effects upon root growth apparent 

 with the soil cultures may have been due to imperfect separation of the 



