34 SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



The effect of green manures. The very definite deple- 

 tion of the yield of rahar under the influence of green- 

 manuring — even when in conjunction with superphosphate 

 — is very remarkable, but it receives some confirmation from 

 the observation recorded above that the introduction of a 

 second leguminous crop led to a slight reduction of the 

 yield. It would almost seem that as if the use of green 

 manures in conjunction with a leguminous crop of the type 

 of rahar were deleterious. It is desirable that- this point 

 should be tested "more rigorously. 



Regarding the cereal crops the returns are very definite 

 and distinctly demonstrate the great benefit derived from 

 green manures, even in purely cereal rotations. The in- 

 troduction of a legume into the rotation gives only a com- 

 paratively small increased benefit. The outstanding- 

 feature is, however, the value of a combination of green 

 manure and superphosphate. 



V. Methods of analysis. 



As recommended by the Chemists' Conference held in 

 February 1919, an investigation of the methods of analysis 

 of nitrogen and phosphoric acid in manures and fertilize 

 has been undertaken at Pusa. Ease of manipulation to- 

 gether with the period of- time involved in the estimations 

 is being taken into consideration along with the accuracy 

 of the results obtained. The results obtained so far are 

 recorded below. 



Nitrogen. Kjeldahi's original method for the estima- 

 tion of nitrogen, and the various modifications which have 

 been proposed by different workers are being closely studied: 

 in this laboratory. It has been found that in Kjeldahi's 

 method where no potassium sulphate is used, as well as in 

 Gunning method where no copper sulphate or mercuric 

 oxide is used, the time taken for boiling is long. In the 

 methods where both copper sulphate and mercuric oxide are 

 used to hasten the decomposition, the chances of oxidation 

 are generally better, but it is still possible to get good re- 

 sults in some of the methods where only one of these is used. 



