INSTITUTE, PUSA, FOR 1919-20 43 



and cultivated plots being 0-3 to 0-2 per cent, and 0-3 to 

 0-1 per cent, respectively. There was a sudden rise in the 

 carbon dioxide in the months July to September. In the 

 grassed plot it rose to 1-5 to 2 per cent., in the trenched 

 plot to 1-0 to 0-9 per cent., and in the cultivated plot to 0-4 

 to 0-5 per cent. This rise seems to be connected with the 

 rainfall and with the movements of the soil water level. 

 From the month of October there began to occur a fall in 

 the carbon dioxide content, this being 1-3 to 0-4, 0'6 to 0-3 

 and 0-4 to 0'2 respectively in the three plots. These rises 

 and falls were most pronounced in the grassed plot and less 

 so in the trenched plot. The variations were of the least 

 magnitude in the cultivated plot. The figures obtained 

 during the year 1920 agree very closely with those of the 

 previous year. 



X. Tobacco experiments. 



Determinations of the dry matters of this season's 

 tobacco have confirmed the observations noted in the pre- 

 vious years that the yield of leaves in the case of ' ' topped 

 plants " is as good or even better than that in the case of 

 " spiked " plants; as regards stems, the yield in case of the 

 " topped " is much higher than in that of " spiked " plants. 



XI. Paddy manurial experiments. 



A series of experiments with local paddy were carried 

 out to compare the effect of ammonium sulphate used as a 

 manure abne and also in combination with green manures. 

 It was found however that — so long as phosphate manures 

 were simultaneously applied — an increasing dose of nitro- 

 gen gave increased yields up to 160 pounds nitrogen to the 

 area. Beyond that point there is a falling off and with 

 320 pounds the yields are little better than with no nitro- 

 gen at all. The tendency was for small doses of nitrogen 

 to increase the proportion of straw to that of grain, but 

 with 80—160 lb. to the acre the increase in grain was 

 greater than that of straw and, consequently, the most eco- 

 nomical application would appear to be between 80 — 160 

 pounds of nitrogen. 



