THE MANURING OF THE CANE. 



"With regard to the effect of manures on the soil, Prof. Harrison comes to 

 the following conclusions, basing his results on the analytical figures obtained 

 by the extraction of the soil in 1 per cent, aqueous citric acid with five hours' 

 continuous shaking: 



1. That the growth of the sugar cane without nitrogenous manuring 

 is accompanied by a considerable loss of the nitrogen in the soil, amounting in 

 ten years to 18'6 per cent, on not limed land, and to 26*7 per cent, on limed 

 land. These are equivalent to losses from the soil to a depth of eight inches 

 of 880 Ibs. and 1250 Ibs., respectively, per acre. 



2. Repeated heavy dressings with farmyard manure have resulted in 

 an increase in the total nitrogen of the soil. In ten years the increase was 

 20-3 per cent., equal to 960 Ibs. of nitrogen per acre added to the soil to a 

 depth of eight inches. 



3. The growth of the sugar cane on plots receiving only nitrogenous 

 manures has resulted in losses of soil nitrogen : where sulphate of ammonia 

 was applied, the loss amounted to 147 percent., or to 670 Ibs. of nitrogen, 

 and where nitrate of soda was used, to 16'3 per cent., or to 775 Ibs. of 

 nitrogen per acre, in the soil to a depth of eight inches. 



4. On soils manured with phosphates, potash, and nitrogen in the form 

 of sulphate of ammonia, the loss of soil nitrogen in the top eight inches 

 amounted to 14*7 per cent., or to 700 Ibs. per acre, while where nitrate of 

 soda was the source of nitrogen the loss was far higher, amounting to 26-5 per 

 cent., or to 1250 Ibs. per acre. 



5. The soil in 1891, at the commencement of the experiments, yielded 

 0142 per cent, of phosphoric anhydride to a 1 per cent, aqueous solution of 

 citric acid. After ten years' cropping without manure it yielded '0086, which 

 shows a loss of nearly 40 per cent, of the probably available phosphoric 

 anhydride, or of, in round figures, 170 Ibs. per acre. 



6. Where the soil received manures not containing phosphates, the 

 proportion of probably available phosphoric anhydride was reduced to -0096 

 per cent., equal to a loss of 32*4 per cent., or to one of, in round figures, 

 140 Ibs. per acre. 



7. Where superphosphates were used in addition to nitrogenous manures, 

 the proportion of probably available phosphoric anhydride was reduced to 

 0-132 per cent., indicating a loss of 7 per cent., or of 30 Ibs. per acre. 



8. Where slag-phosphates had been applied, the probably available 

 phosphoric anhydride has been reduced to '0102 per cent., equal to a loss of 

 28*1 per cent., or to one of 120 Ibs. per acre. It is worthy of note that in 

 our more recent experiments, while manuring with slag-phosphates produced 

 on the plots which had received superphosphates during the earlier years of 

 the experiments mean increases of only 2-3 per cent., they produced on those 

 which had been manured with slag-phosphates a mean increase of 5-8 per 

 cent. 



57 



