t 94 ] 



derbans have to be drained of their excess salt before they 

 become fit for cultivation. The Usar or barren lands of the 

 N. W. P. usually contain an excess of sodium carbonate or 

 sodium sulphate which are locally called Reh. These lands 

 are being reclaimed by drainage, enclosure and light manur- 

 ing. In 1895-1896 Dr. Voelcker determined by a series of 

 carefully conducted experiments, the proportions of different 

 sodium salts which might be present in a soil without pre- 

 venting plant growth. To good garden soil, which was 

 shown to contain no appreciable amount of any of the sodium 

 salts, were added definite amounts of the three salts, sodium 

 carbonate, sodium sulphate and sodium chloride. The 

 amounts of salt varied from -i to i%. Cereals and pulses 

 were sown in separate pots. It was found that each of these 

 salts retarded the germination. The cereals were affected by 

 7% of carbonate or sulphate and by -4% of chloride. The 

 germination of the pulses was retarded by smaller amounts, 

 i.*., by -2 to -4% of Carbonate or chloride and -7% of Sulphate. 

 In the after-growth -2 per cent, of the carbonate did harm 

 whilst -4 per cent, was quite fatal. Up to '2/ Q of sodium Chloride 

 was formed harmless in a few cases whilst 'i% proved harm- 

 ful in others. Sodium sulphate was less harmful, perfect 

 growth both in the kharif and rabi seasons being maintained 

 in the presence of "5% of the salt. As in germination so in 

 the after-growth, the leguminosae were affected more than the 

 cereals by the excess of soda salts. From this experiment it 

 may be inferred how the lands reclaimed in Sundarbans though 

 they become fit for growing rice very readily, are found 

 unsuitable for pulse crops for a long time. 



(5) Another cause of the barrenness of Usar lands is 

 their impermeability to water. 



(6) Waters from 'mines containing aluminium and mag- 

 nesium salts often prove poisonous to plants, also waters 

 containing copper, lead and other heavy metals, in solution. 



