35^ 



Silt of Rivers as Manure. 



Bengal and in districts where they are dammed up for 

 irrigation purposes, whereby the fertility of the land is in- 

 creased. Where tanks are employed as irrigation agents the 

 mud which collects in them is frequently dug out and 

 applied to the land as a fertiliser. Not all the silt carried by 

 rivers is of manurial value, for it appears that in the Hoshiar- 

 pur District in the Punjab enormous quantities of sand are 

 brought down from the hills during the monsoon and cover 

 up the good soil. 



Exact information on the agricultural value of silt appears 

 to have been almost entirely wanting until the recent comple- 

 tion of experiments by Dr. J. W. Leather, Agricultural 

 Chemist to the Government of India, who, in 1893, com- 

 menced to test the manurial value of the silt which is 

 generally carried on to the land by canal water. It was first 

 attempted to carry out the investigation as a field experiment, 

 and fields were accordingly embanked and the canal water 

 run on during the monsoon. A crop was then taken in 

 the following cold weather from this, as also from a con- 

 tiguous field, to which no canal water was applied during 

 the monsoon. It was found that the amount of silt and its 

 contents of nitrogen and phosphoric acid are but very small 

 during the cold weather, and quite insufficient to replace the 

 plant food taken from the soil by a crop of wheat. On the 

 other hand, it would appear to be certain that the silt carried 

 on to the land during the monsoon period contains very 

 material quantities of these plant foods, and that they are 

 probably fully sufficient to replenish the amounts which are 

 taken from the land by the rice crop. 



The results obtained are said to be in agreement with the 

 general practice in regard to rice cultivation in India, where 

 rice lands are rarely manured. They are usually clays, and 

 the water passes from one field to another, removing and 

 depositing silt at the same time. Rice lands may thus be 

 said to annually receive a certain amount of silt from 

 higher levels, and this reason is given as a probable explana- 

 tion of the fact that these rice lands " can do without manure 

 better than any other sort of lands." 



