iQig] CURRENT LITERATURE 481 



results, and significance of these experiments can best be presented by quota- 

 tions from the summaries of the two bulletins: 



"The general plan of the field experiment, which is the main subject of this 

 bulletin, is to grow 16 different crops on that number of plats for two seasons 

 prior to growing a different one of the crops over the entire area every third 

 year. No farm manures are used, but fertilizer chemicals are applied on all 

 plats alike, in amounts intended to supply an average of the nutrient needs of 

 the different crops. Information regarding these needs is obtained by soil 

 tests conducted in pots at the greenhouse and in sections of drainpipe sunk in 

 the paths between the field plats. 



"Onions occupied the entire area in 1910. If the preceding crops are 

 arranged in the order of increasing yields of onions of the first class, it is seen 

 that 13-17 bushels of onions per acre were produced following cabbages, mangel 

 beets, rutabaga turnips, and buckwheat; 35 and 87 bushels following potatoes 

 and rye; 131-178 bushels following corn, millet, onions, oats, and red clover; 

 240-314 bushels following squash, timothy, and alsike clover; and 406 and 

 412 bushels following mixed timothy and redtop, and redtop alone. 



"In 19 13, after the miscellaneous crops had been grown on their respective 

 plats again for two years, buckwheat was planted on the entire area. Again 

 arranging the crops in accordance with increasing yields, it follows that only 

 4-10 bushels of buckwheat grain were produced where millet, grasses, corn, 

 and clovers had been growing previously; 13-15 bushels where buckwheat 

 and oats were the preceding crops; 20-23 bushels where the preceding crops 

 had been cabbage, beets, onions, rye, squashes, and potatoes; and 34 bushels 

 following turnips. 



"Alsike clover was chosen for the crop next grown on the entire area. The 

 lowest total yields of clover hay for the two years 1916 and 191 7 were 2.53- 

 2 .60 tons per acre, following the clovers and carrots. The highest yields were 

 4.16-4.33 tons, following rye and redtop, and two years' failure of squashes. 

 Intermediate yields of 3.31-3.86 tons were secured following the remaining 

 crop plants. 



"The divergent efifect of crops on those which follow seems not to be attrib- 

 utable, at least principally, to differences in the amount of nutrients removed 

 by the crops grown previously; that is, the smallest yield may not occur after 

 the crop which removed the largest amount of even the most-needed nutrient. 

 The soil acidity was affected differently by the several crops and, generally, 

 the best yields of the onion, a plant which is sensitive to conditions accom- 

 panying acidity, followed the crops giving rise to the least acidity. These 

 indications assume added importance because of the observed fact that the 

 effects of the crops on those which foUow were much less divergent if the soil 

 acidity was reduced by liming. 



"Even if later work should prove that preceding crop effects are not impor- 

 tant in connection with a neutralized soil, attention should nevertheless be 

 given by the practical farmer to the very potent influences which have been 



