April 1933] FERTILIZER EXPERIMENTS ON "rUN-OUT" HAY LAND 7 



From the manner in which the increases from these materials (Table 

 III) parallel each other for the first three years, it seems reasonable to 

 conclude that manure benefited the alfalfa because of the potash it con- 

 tained. At the end of three years, the response from manure became 

 stationary or declined slightly, while the plots receiving fresh applica- 

 tions of potash gave even greater increases than they had the first three 

 years. 



A study of Table III indicates, too, that it is unwise to judge the 

 response for a substance like potash on the basis of one season's results. 

 The increase for 1927, for example, was too small to detect with the 

 eye. As the seasons progressed the differences between the potash 

 plots and the check plots became more marked, the former showing a 

 thicker and more vigorous stand. In 1931 the yield of these potash 

 plots was almost double that of the checks. 



With muriate of potash at $50 per ton and alfalfa hay at $20 per ton, 

 each dollar invested in potash returned about four dollars' worth of 

 hay. Manure gave a return of about $3.50 per ton in increased hay 

 yields. 



Potash was not used alone with the 20 tons of manure applications. 

 It was used in combination with phosphorus and with nitrogen and 

 phosphorus in the MLPK and MLNPK combinations. Yields of these 

 two series (Table II) show that with manure and other elements, pot- 

 ash stimulated the growth and yield of alfalfa. The average annual 

 yield of the MLNPK plots was 7,772 pounds, or 3.89 tons of hay per 

 acre for the five-year period. 



The results for superphosphate (P) are not so encouraging. A study 

 of Table II indicates that the response from this substance is some- 

 what better when used with lime or manure, or manure and lime, than 

 where used alone. The response for the LP treatment when compared 

 with lime (L) alone gives a significant increase, but none of the other 

 comparisons are significant. 



The value of superphosphate as a material for top-dressing is doubt- 

 less limited by the fact that after it is applied, it is quickly absorbed or 

 fixed in the first inch or two of top soil. As few of the feeding roots 

 of alfalfa are in this layer, the full effect of the superphosphate is not 

 obtained by the crop. 



The soil of this field is quite well supplied with phosphorus, a chemi- 

 cal analysis revealing the fact that in the top soil alone there are al- 

 most 1,800 pounds of this element. Liming and manuring may have 

 made these stocks available at a sufficiently rapid rate to supply most 

 of the needs of the crop. 



While all of the increases for superphosphate where comparisons are 

 available are positive and indicate that some benefit has been obtained 

 from its use, it does not seem advisable to make such heavy applications 

 of this substance as applied in this test, except at seeding when the 

 material can be worked deeply into the soil. 



The results for nitrate of soda (N) are not significant nor encourag- 

 ing enough to warrant the purchase of nitrogenous fertilizers for top- 

 dressing alfalfa, where an abundance of manure is used prior to or at 



