INSTITUTE, PUSA, FOR 1916-17 27 



VI. Starch. 



The experiments on sweet potatoes (Ipomoea batatas) 

 referred to in last year's report have been continued. Five 

 varieties were grown on manured and unmanured soils. 

 The effect of manuring was clearly marked in all the plots 

 and it would appear that the application of manure would 

 pay in the cultivation of sweet potatoes. 



Last year's result, that the best time of harvesting the 

 crop is the middle of February, was confirmed this year. 

 The analyses made show that the percentage of starch in 

 the tubers continues to rise till about this time, after which 

 it remains practically constant. There was, however, this 

 year a well-defined increase in the yield of tubers after 

 February, probably owing to rains which fell during the 

 first week of February. It is possible that irrigation of 

 the crop during the latter stages of growth would increase 

 the output. 



A point of practical importance is that if the manu- 

 facture of starch be taken up on an estate, it might be in- 

 advisable to restrict manufacture solely to the sweet potato 

 as the latter would be available only during a short period, 

 namely, about two or three months. In Bihar there is 

 another root crop which is also very suitable for the manu- 

 facture of starch and comes on to the market at a different 

 time of year. This is the suthni {Dioscorea fasciculata) 

 mentioned in last year's report. If both crops are utilized 

 the manufacture of starch would be continuous from Nov- 

 ember, when the harvest of suthni begins, until the end of 

 January or early February when the crop of sweet potato 

 would become available and enable manufacture to be con- 

 tinued until March. In July and August a second crop 

 of sweet potatoes would be obtained and could be utilized. 



A sample of starch manufactured from sweet potato 

 (Ipomoea batatas) here has been very favourably reported 

 on by Messrs. Reckitt & Sons, Ltd., Hull, who state that at 

 the present time such a product would sell very readily in 

 Great Britain for industrial purposes provided that the 



