4 RESULTS OF EXPERIMENTS AT ROTHAMSTED, 



readily available nitrogenous accumulations. Thus, over the second 

 half of the period, the Wheat gave 17 -2, and the Barley 18-8 Ibs., 

 against 16'4 Ibs. over 30 years in the various root-crops. 



We now come to the yield of nitrogen in Leguminous crops, grown 

 under somewhat similar circumstances as to the soil supplies of it. 

 Referring first to the results obtained with Beans, it is seen that, over 

 the first half of the period of 24 years, the average annual yield of 

 nitrogen in the crop was 61-5 Ibs. per acre; whilst, over the second 12 

 years, in 3 of which, however, the crop failed, so that there were only 

 9 years of Beans, 1 year of Wheat, and 2 years of Fallow, the annual 

 yield was less than half as much, or only 2 9 -5 Ibs. per acre. Never- 

 theless, the average yield over the 24 years without any nitrogenous 

 manure, was 45 '5 Ibs. per acre per annum. That is to say, under very 

 similar conditions as to soil supply, the highly nitrogenous Leguminous 

 crop, Beans, has yielded over a given area, twice as much nitrogen as 

 either Wheat or Barley, and more than twice as much as the root-crop. 



The next results relate to the Leguminous crop, Clover. It is 

 well known that Clover fails when it is attempted to grow it too 

 frequently on the same land ; and in the case recorded in the Table, it 

 happened that Clover was obtained in only 6 years out of the 22 for 

 which the yield of nitrogen is given ; so that there are included, owing 

 to the failures, 1 year of Wheat, 3 years of Barley, and 12 of Fallow. 

 Notwithstanding this, there was, with the occasional interpolation of 

 the Clover, an average yield, over the 22 years, of 39*8 Ibs. of nitrogen 

 per acre with mineral, but without nitrogenous supply. 



The last results in the Table relate to the yield of nitrogen per acre 

 per annum, over 32 years of an actual rotation of crops ; that is, over 

 8 courses of 4 years, each course comprising Swedish Turnips, Barley, 

 Clover (or Beans), and Wheat, which, as in the other cases, were grown 

 with a purely mineral manure (in this case superphosphate of lime 

 alone), but without any nitrogenous supply. 



The figures show that, when the various crops are thus grown in 

 alternation one with another, instead of each separately year after 

 year, on the same land, the yield of nitrogen is generally greater, 

 and sometimes much greater. Thus, whilst the mineral manured 

 Swedish Turnips, yielded only 18*5 Ibs. of nitrogen per acre per annum, 

 when grown year after year on the same land, they yielded 33*3 Ibs. 

 when grown in rotation ; the Barley yielded 2 2 -4 Ibs. when grown 

 continuously, and 23-5 Ibs. in rotation; the Beans 45-5 Ibs. grown year 

 after year, and only 40'5 Ibs. in rotation, but this is very much more 

 than the yield of the continuous Beans in the second half of the period, 

 which was only 29'5 Ibs. ; the Clover yields an average of 124-5 Ibs. 

 in rotation, against only 39 '8 Ibs. when it was attempted to grow it 

 continuously, and it frequently failed ; and the Wheat succeeding the 

 Leguminous crop in rotation, yields 35-9 Ibs. against only 221 Ibs. 

 grown continuously. Lastly, the rotation crops taken together (including 

 Leguminosce), have yielded, over 32 years, an average of 38 '6 Ibs. of 

 nitrogen per acre per annum, against only about half as much in either 



