74 CROP GROWING AND CROP FEEDING 



potash called " double manure salts/ 7 or the double sulphate of potash and 

 magnesia. This is a lower grade, and contains from 23 to 26 per cent, of 

 potash. From the lower percentage of potash this, like kainit, is more costly 

 so far as the actual potash is concerned, and it is always more economical, 

 especially where the goods are to be transported far from the port of entry, 

 to buy the most concentrated article and thus avoid the freighting of useless 

 matter. 



CAPACITY OF THE SOIL FOR ABSORBING POTASH. 



In some instances, near the coast, it is found that kainit is the cheaper 

 form in which to buy potash. But to get the amount of potash needed by the 

 early potato crop, for instance, would require an application that would be 

 certain to be injurious from the amount of sodium chloride if directly applied 

 to the crop. Fortunately it has been found that while the soil will release 

 the chloride of sodium and allow it to leach away, it will hold on to the potash 

 that was associated with it. Therefore, it has become the practice with a 

 few growers near the coast to apply a heavy dressing of kainit in the fall, 

 to the land they intend planting in potatoes in the spring. The injurious 

 chloride is leached out of the sandy soil during the winter, while the potash 

 remains. It also seems probable that the chloride in the leaching may render 

 soluble other matters in the soil that may be of use, and thus help the crop. 

 But this very fact may be a disadvantage, since there may be formed soluble 

 chlorides of lime, and the heavy application of kainit may result in the ex- 

 haustion of the lime in the soil. But where this practice is followed, the 

 abundance of marine shells at hand will soon remedy this, if used on the soil 

 after burning. There are few localities, however, where kainit is the cheapest 

 form of potash. The application of potash should in any event, be immedi- 

 ately worked into the soil, so that it may be equally diffused in the soil and 

 not fixed merely at the surface. 



DANGERS FROM POTASH. 



The general opinion is that kainit is especially dangerous in contact with 

 seeds or young plant roots, by reason of the large percentage of salt which it 

 contains. This is true, but in our own experiments we have found that the 

 muriate is far more damaging to germination of seeds with which it comes in 

 contact, than kainit is. Carefully conducted experiments have shown that 

 even when covered with an inch of soil, seeds placed above the muriate were 

 seriously damaged. In fact, no fertilizer containing a large percentage of 

 potash should be used in direct contact with the seed, and it is far better that 



