Manuring Experiments with Paddy Rice, 
BY 
Dr. O. Kellner, Y. Kozai, Y. Mori and M. Nagaoka. 
It is a well established fact that of the nutrients required by 
crops some exist in the soils and ordinary manures in sufficient 
quantities, and need not be specially cared for in farming, while 
others are less copious and must be carefully taken into ac¬ 
count in the application of manures. These latter nutrients 
are : nitrogen, phosphoric acid, potash, and sometimes, though 
rarely, lime. Manuring experiments, which tend to reveal the 
needs of a soil or crop, have accordingly to deal chiefly with 
these four nutrients and to ascertain what quantity and form 
of each is the most suitable and economical under given con¬ 
ditions. 
In making researches of this kind the so-called “ law of the 
minimum factor ” plays an important part. According to it, 
the material produce by crops depends upon that essential fac¬ 
tor of production which is least available to the crops. For 
instance, if a soil is well supplied with nitrogen and potash and 
all other conditions are favorable to a normal produce, but 
if at the same time phosphoric acid is available only in a small 
proportion, the yield of the crop will be determined by this 
latter nutrient ; if only water is deficient in the soil, the yield 
depends on this factor of growth, etc. Hence, if we wish to 
find out whether any, and if so, how much of a certain nutrient 
is to be applied to a certain soil and crop, we have to arrange 
a series of experimental plots and to supply them with so much 
