242 



THE ROTHAMSTED EXPERIMENTS. 



Potash 

 manures 

 for legu- 

 minous 

 crops. 



Potash in 

 grain and 

 straw of 

 wheat. 



With superphosphate alone, whilst the beau crops contained 

 only 10.82 and 12.80 lb. of potash, the clover contained 57.63 

 and 65.48 lb. That is, under the influence of the phosphatic 

 manure, probably partly on the plant and partly on the soil, 

 the clover had accumulated in the removed crop five or six 

 times as much potash as the beans, from the soil itself; 

 whilst, of the phosphoric acid itself, little more than twice as 

 much was taken up in the clover as in the beans under the 

 influence of the superphosphate without potash. It would 

 thus appear that the beneficial effects of the phosphatic 

 manure on the clover were largely connected with the 

 increased capability of the plant to take up more potash. 



With the mixed manure, supplying a large amount of 

 potash, the amount of it found in the clover crops was, how- 

 ever, much greater still. Both in the beans and in the clover 

 the amount of potash in the crops grown under the influence 

 of the direct supply of it was about twice as much as those 

 grown with superphosphate without potash. But whilst, 

 under the influence of the supply of it, the shorter-lived, more 

 meagrely rooting, and less successfully grown bean crops 

 stored up only 22.16 and 24.46 lb. of potash, the clover crops 

 contained in one case 123.12 lb., and in the other 132.62 lb. 



The very much larger proportion of the total potash of the 

 bean crops which is found in the corn than in the straw would 

 seem to indicate its greater importance in connection with the 

 maturing than with the merely vegetative and accumulating 

 tendencies of growth ; yet the increased amount of it taken 

 up by the beans coincidently with increased growth, and the 

 much larger amounts of it in the clover with its much greater 

 amounts of growth and produce, and harvested as it is in the 

 unripened condition, are on the other hand indications of a 

 direct connection between potash supply and the luxuriance 

 of growth or vegetative activity of these leguminous crops. 

 Indeed, as already referred to, potash manures are well known 

 to be frequently beneficial to such crops. To these points 

 further reference will be made presently, when calling atten- 

 tion to the amount of lime taken up by leguminous crops. 



The Potash in the Wheat Crops. — The results on this point 

 are given in the bottom division of Table 64. 



It has been seen that by far the larger proportion, both of 

 the nitrogen and of the phosphoric acid of the wheat crops, 

 was accumulated in the grain. But the figures relating to 

 the potash show that of it there was very much more in the 

 straw than in the grain. There was also much more, but not 

 in so great a degree more, in the straw than in the grain of 

 the other cereal — the barley. It has been pointed out that 

 potash is at any rate essentially connected with the formation 



