386 V. KOZAI, M. TOYONAGA AM) M. NAGAOKA. 



the phosphoric acid left in the soil is pretty rapidly converted into 

 the forms which are but difficultly assimilable by plants. It is 

 consequently advisable to apply phosphoric acid, at least in the 

 case of soluble phosphatic manures to each crop according- to its 

 want. The same fact has also been noticed by Maercker with 

 different kinds of soils. The conversion of easily soluble phosphates 

 into the forms not easily assimilable by plants is much favoured by 

 the presence of hydrated sesquioxidcs of iron and aluminium, which 

 are present in extremelj- large quantities in our soils. In other kinds 

 of .soils the conversion will not be so rapid as in the soil under 

 experiment. 



III. SERIES. 

 After Effect of various Pliosphatic Manures. 



{Tfii>-<i, Fourth a>id Fifth Years ^ 



These experiments were commenced in 1S90 and were con- 

 tinued until last year for determining the after effect of various 

 phosphatic manures. They were made Avith 57 ^alots with 9 differ- 

 ent kinds of manures, .so that 6 plots were used for each manure, 

 3 with a small dose and 3 with a large dose, the latter being just 

 double of the former, while the remaining 3 plots were left without 

 any phosphatic manure. After harvesting the crop these plots were 

 always left untouched until the May of the next year, when their 

 soil was well mixed with water. In the middle of June they were 

 supplied with 10 kilogrms. of nitrogen as ammonium sulphate and 

 10 kilogrms. of potash as carbonate. The average yield of the third 

 experimental year (1892) is shown in the following table: 



'"Landwirthfcliafliclie Jalirbiicbcr. VA. XXIT. (1893). Ei-gaiizung>l).in(l II. p. 37. 



