12 



manure increased tlie yield of nitrogen but little. Not so in tLo case 

 of the leguminous crop, beans. During the first twelve years, the 

 complex mineral manure (containing a large amount of potash) 

 yielded 61'5 pounds of nitrogen per acre per annum, against 48'1 

 pounds without manure. During the next twelve years, the mineral 

 manure gave 29"5 pounds, against only 146 pounds without manure. 

 Daring the whole period of twenty-four years, the potash manure 

 yielded 45 "5 pounds of nitrogen per acre per annum, against 

 31"3 pounds without manure. Lastly, with the mixed mineral manure 

 beaui. have yielded over a period of twenty-four years more than 

 twice as much nitrogen per ncre as either whaat or barley. 



But notwithstanding that the beans have for a long series of years 

 yielded so very much more nitrogen over a given area than either of 

 the gramineous crops, and much more also than the root-crops, the 

 significant fact cannot fail to be observed that this crop of the legu- 

 minous family, which is supposed to rely almost exclusively on the 

 atmosphere for its nitrogen, has declined in yield as strikingly as the 

 other crops, even when grown by a complex mineral manure, con- 

 taining a large amount of potash. Why should this be so if the 

 supply of nitrogen is from the atmosphere and not from the soil ? 



The results next recorded relate to red clover, and the period of 

 experiment was twenty-two years. It is well known that on most 

 soils a good crop of clover cannot be relied upon oftener than once in 

 about eight years, and on mauy soils not so frequently. It will not 

 excite surprise, therefore, that in the course of the twenty-two years 

 of experiment, in only six was any crop of clover obtained, and in 

 some of those only poor ones. Indeed, the plant failed nine times out 

 of ten during the winter and spring succeeding the sowing of the 

 seed. In one year a crop of wheat, and in three years barley, was 

 taken instead ; whilst in the remaining twelve years the land was left 

 fallow after the failure of the clover. Still the annual yield of 

 nitrogen over the twenty-two years was 30'5 pounds without any 

 manure, and 39"8 pounds by a complex mineral manure containing 

 potash. Unfavourable as is this result in an aj^ricultural point of 

 view, it is still seen that the interpolation of this leguminous crop has 

 greatly increased the yield of nitrogen compared with that in either 

 wheat or barley grown continuously ; and here again, as with beans, a 

 potash manure has considerable increased the yield. 



The next experiment afforus a still more striking illustration of the 

 large amount of nitrogen that may be taken up in a clover crop ; and 

 it further illustrates the fact, well known in agriculture, that the 

 removal of this highly nitrogenous leguminous crop is one of the best 



