162 BOAED OF AGEICULTURE. 



Dr. Eiggs. They take off the first crop, and plow m the 

 second. 



Prof. Johnson. There are some further facts in regard to 

 clover which are very interesting. Dr. Yoelcker, who has 

 been Chemist to the Royal Agricultural Society of England for 

 the last twelve years, when he was formerly in the Royal Agri- 

 cultural College at Cirencester, found that some of the farm- 

 ers in the vicinity not only thought that clover was an excel- 

 lent preparation for wheat, but asserted that the wheat did 

 better when, instead of plowing in the second crop, th.ey took 

 it off. The doctor we may suppose was rather incredulous ; 

 but he found other farmers who said, " Our wheat does best 

 when we let the clover ripen, and save the seed, and put the 

 wheat in after that." These opinions were put to him in such 

 a way that he could but candidly say, " It would be folly to 

 deny such statements on my knowledge of what is probable ; 

 I will look into the- matter, and satisfy myself by my own 

 trials. I am living here on the ground, and I can make the 

 experiments, and if it be true, that taking off two crops of 

 clover leaves the soil in better condition for wheat than when 

 one crop is taken off, if I examine the soil when one crop has 

 been taken off and when two crops have been taken off, I 

 ouglit to find more available nitrogen and more available 

 phosphoric acid in a given quantity of soil in the latter case 

 than in the first case ; and if it be true, that where tlie plant 

 has been allowed to go to seed, the preparation for wheat is 

 still better than in the other two cases, I ought to find still 

 more of those materials." He made the investrgation, and 

 actually found that the quantity of those nutritive materials 

 left in the surface-soil after the clover seed had been taken off 

 was greater than when two crops of clover hay had been cut, 

 and greater when two hay crops had been removed than when 

 only one had been taken off. That is due to the fact, which 

 I have already insisted upon, that the clover plant, after pro- 

 ducing its seed, is still able, when the character of the soil is 

 adapted to it, to continue its growth and bring up to the sur- 

 face-soil those materials which the wheat plant cannot reach. 

 We cannot, from cases of this sort deduce rules of universal 



