3 6 
MANURING EXPERIMENTS WITH PADDY RICE. 
young plants applied per plot there were only 0.087 grins., the 
amount absorbed from the soil was 0.519 grms., and as from 
the phosphoric acid only 21.5% can be taken up by the plants 
(p. 32), the available quantity is found to be per plot 2.41 grms. 
or per tan 2.60 kilogrms. of phosphoric acid, equivalent in 
efficacy to phosphoric acid soluble in water. 
Finally, as regards potash, the crop produced without any 
supply of this nutrient but with copious nitrogen and phos¬ 
phoric acid, contained 4.78 grms., from which quantity 0.19 
grms. must be deducted as having already been in the young 
plants. Hence 4.59 grms. of potash had been taken up from 
the soil. As from moderate doses of potash manure rice plants 
are capable of consuming 50%, the stock of available potash in 
our soil is 9.18 grms per frame or 10 kilogrms. per tan. 
By adding to the stock of available nutrients thus calculated 
the amounts of nitrogen and phosphoric acid 15 needed as 
manure on our soil, we get figures which express the quantity 
of nutrients needed by a full rice crop under the climatic con¬ 
ditions and mode of cultivation of our neighbourhood. 
Kilogrms. per tan : Nitrogen. Phosphoric. 
acid. 
Needed in the manure, 7.5 12.5 
Contained in the soil 12.6 2.6 
Total 20.1 15.i 
If these results should be confirmed by researches on other 
soils and under other conditions, they would represent a most 
important basis for the determination of the amount of fertili¬ 
zers to be applied to rice. By three trials, viz. 
1) 15 kilogrms. of phosphoric acid and 12.5 kilogrms of nitro¬ 
gen ; 
2) 15 kilogrms. of phosphoric acid and 15 kilogrms. of potash ; 
3) 12.5 kilogrms. of nitrogen and 15 kilogrms. of potash ; 
each of which must be carried out on 3 or 4 small plots, and by 
16 As the 10 kilogrms. of available potash per tan of our unmanured land 
appeared to suffice to the crops, we cannot, of course, extend our calculations 
to this nutrient. 
