372 



V. KOZAT, M. TOYOXAGA AND M. XAGAOKA. 



plots and kept constantly filled with water. Toward the end of 

 September, tiie irrigation was stopped as is usually done by farmers, 

 and the water was afterwards given only for two days at the time 

 of flowering. Tlie variety of rice cliosen for these experiments was 

 " Satsuma," since its vegetation jjeriod is of medium length. In 

 1892 the weather was fairly good, but in 1893 it was very unfavour- 

 able, while in 1894 it Avas exceedingly favourable. 



I. SERIES. 



Exhaustiou of Soil Nutrimeats by tlie Successive Cultivation of 

 Rice and the Quantity of the Fertilizer required for the 

 Soil to recuperate, as judged by the Quantities 

 of Nutriments contained in the Crop. 



As alread) stated, these experiments were carried on in order 

 to ascertain the quantity of each of the three essential nutriments 

 which the soil may yield to the rice in the j^lots not supplied with 

 the respective nutriments but manured with the other essential 

 nutriments, and to determine the nutriment required by the soil, 

 as inferred from the quantities of nutriments contained in the crop. 

 The plots used in these experiments were those that had served the 

 same purpose in the preceding years. The quantities of nutriments 

 supplied to the plots were the same every year, and were as follows 

 (per tan =0,0992 hectare) : 



1) 3 plots were left unmanured. 



2) 3 plots did not receive any phosphatic manure, but were 

 supplied with 10 kilogrms. of nitrogen and 10 kilogrms. of potash. 



3) 3 plots did not receive any nitrogenous manure, but were 

 supplied with 10 kilogrms. of phosphoric acid and 10 kilogrms, of 

 potash. 



4) 3 plots did not receive any potassic manure, but were sup- 

 plied with 10 kilogrms. of jihosphoric acid, and 10 kilogrms. of 

 nitrogen. 



5) 3 plots received a comjDlete manure containing 10 kilogrms, 

 of nitrogen, 10 kilogrms. of phosphoric acid, and 10 kilogrms. 

 of potash. 



In these experiments, nitrogen was supplied in the form of 

 ammonium sulphate, phosphoric acid in that of double superphos- 

 phate and potash in that of carbonate. 



