MANURING EXPERIMENTS WITH PADDY RICE. 



Peruvian guano and Thomas phosphate showed their effect longest, 

 the effect being still visible in the fifth season after application. 

 Bone ash and phosphorite had rather a small after-effect, although 

 the richness of our soil in acid humus must favour the decomposition 

 of insoluble calcic phosphate. 



Now for the purjoose of getting an information as to the relative 

 efficacy of the various phosphatic manures we have calculated from 

 the above table the following figures, taking into account only the 

 extra-yields of grain caused by the smaller doses of phosphoric 

 acid : 



Kiivl of phos- 

 phntic manure. 



Increase of full tjrain caused by 

 100 grms. of phosphoric acid 

 applied in 1890. 



Relative increase, action 

 superphosphate = 100. 



ill the 1st: 

 season. 



in the 1st & 

 2nd seasons, 

 (inns. 



in the Isi, 

 2nd A 3rd 

 ; seasons. 



= ->■: 



- £S 



in tne 1st 

 season. 



Gnus. 



aj E 3 

 — N X r 



^■^ S 3 



S 3 



i » 



X S 



c =-g 



to ^ . 



— CO ^ 



" -- ^ 



"IS 



Double super- 

 pliosphate 



6247 



7121 



7121 



7661 



7661 



100. 



100. 



100. 



100. 



100. 



Precipitate 1 phos- 

 phate 



6688 



7756 



8366 



S824 



8824 



107. 1 



108.0 



117.4 



1 1(5.5 



116.5 

























Peruvian i^uano.. 



2095 



384s 



414& 



4405 



4892 



33-5 



54-0 



5S.2 



57.5 



63 -9 



Thomas phos- 



3093 



5025 



5563 



6I5S 



^'434 



49-5 



70.6 



78. 1 



80.4 



84.0 

























Steamed lione 



2326 



5388 



5664 



6004 



6004 



S3o 



757 



79-5 



783 



78.3 



Crude bone dust 



3762 



5229 



5432 



591 1 



591 1 



60.2 



73 4 



764 



77.2 



77.2 



Bone ash 



1816 



2309 



2687 



2760 



2760 



29.1 



324 



37-7 



36.C 



36,0 



Phosphorite 



813 



1394 



1714 



2004 



1 



2367 



13.0 



1 



194 



1 



24.1 



26.2 



1 



309 



Before entering into a discussion of these results we shall con- 

 sider the proportion of phosphoric acid absorbed by the plants 

 from the residual phosphates. Chemical analysis of tlie crop of 

 1892 gave the following results : 



