894 EXPERIMENT STATION RECORD. 



beans) or bare fiillow, and (4) wheat. One section of the field has 

 received no fertihzers since the experiments began. On the other two 

 sections fertilizers were applied only to the root crop, hence only once 

 in 4 years. In the second section minerals only were used, superphos- 

 phate alone being applied in the first 9 courses (3G years), supple- 

 mented in succeeding courses by salts of potash, soda, and magnesia. 

 The third section of the field received a complete fertilizer, supplying, 

 in addition to minerals, 140 lbs. of nitrogen every fourth year, equiv- 

 alent to an average annual application of 35 lbs. \)er acre. Tliis com- 

 plete fertilizer consisted of superphosphate, salts of jjotash, soda, and 

 magnesia, and rape cake. 



In each section the turnips on half the area devoted to this crop 

 were fed on the land ; on the other half both roots and leaves were 

 permanently removed. 



Crop yields under different conditions. — The turnip crop, sometimes 

 regarded as a restorative crop, gave practically no yield without fer- 

 tilizers. Superphosphate largely increased the yield, a result regarded 

 as largely due to its increasing the growth of feeding roots in the sur- 

 face soil, and thus enabling the turnip crop to quite completely exbaust 

 the nitrogen previously accumulated in the soil. Hence soil fertility is 

 very rapidly exhausted by growing and removing a turnip crop ferti- 

 lized with superphosphate alone. 



Tlie addition of nitrogen to the mineral fertilizer practically doubled 

 the yield obtained from superphosphate. 



On the unmanured section the crop of turnips was so small that it 

 mattered little, as shown by subsequent crops, whether it was removed 

 or retained. On the section treated with superphosphate, feeding 

 turnips on the land increased the yield, and the advantage of this 

 practice was still more marked on the more productive area supplied 

 with a complete fertilizer. The yield of turnips was practically identi- 

 cal wht'ther the field was fallowed or in a leguminous crop 2 years 

 previous. 



Barley, the second crop of the course, suffered less from the absence 

 of fertilizers than did turnips, the average yield of the unfertilized sec- 

 tion being more than 30 bu. per acre. This was attributed to the 

 thorough preparation for barley, viz, the clean cultivation of turnii)S, 

 and to the slight draft made on the soil by the small (unfertilized) 

 turnip cro]>. Naturally the removal or retention of the small turnip 

 crop did not affect the yield of barley. On the plats on which turnips 

 treated with superp!iosi)hate had yielded fairly well, the feeding of the 

 turnips on the land considerably increased the yield of barley. How- 

 ever, on the section thus manured the removal of the turnip crop so 

 far exhausted the soil as to reduce the yield of barley below the yield 

 on the unfertilized section. A complete fertilizer applied to the pre- 

 ceding turni]) crop largely increased the yield of barley, especially on 

 the plats on which the heavy turnip crop had been fed. 



