32 HATCH EXPERIMENT STATION. [Jan. 



4. The low-grade sulfate of potash ranks third ; but, as 

 freights cost more per unit of potash for this salt than for 

 the high grade, the latter is generally to be preferred. It 

 is not impossible that in some localities the magnesia of the 

 low-grade sulfate may prove useful ; but we have no evi- 

 dence that such is the case here. 



5. The kainite ranks lowest among all the salts em- 

 ployed. Since this, containing only about 13 per cent, of 

 actual potash, can be purchased at a much lower ton price 

 than the purer salts, such as the high-grade sulfate and the 

 muriate, it is sometimes selected by farmers. It should be 

 remembered that the unit of potash on the farm usually 

 costs more in the kainite than in the others. In view of 

 our results, then, I can see no reason for selecting this 

 potash fertilizer. 



6. The silicate of potash gives the next lowest crop. It 

 is apparently slowly available. The present cost is high, 

 and it can be kept from caking only l)y admixture with 

 powdered peat or similar material. It is prepared espe- 

 cially for use on tobacco, for which crop it is under trial in 

 Germany and in this country. I judge it will have no ap- 

 plication for ordinary crops ; and its usefulness for tobacco 

 is not fully demonstrated, though some favorable results 

 have been obtained. 



Leguminous Crops (Clover, Pea and Bean or "Pod" 

 Family) as Nitrogen Gatherers. (Field A.) 

 This experiment is a continuation of a series begun in 

 1889. The objects in view have been : — 



1. To determine the extent to which plants of the clover 

 family are capable of enriching the soil in nitrogen taken 

 by them from the air through the agency of the nodular 

 bacteria found upon their roots. 



2. To compare nitrate of soda, sulfate of ammonia, dried 

 blood and farm-yard manure as sources of nitrogen.* 



The plots, eleven in number, are one-tenth acre each, and 

 are numbered to 10. Three plots (4, 7 and 9) have re- 



* Only such details are given here as are necessary to an understanding of the 

 nature of the experiment. Full particulars will be found in our ninth and tenth 

 annual reports. 



