Apeil 21, 1911] 



SCIENCE 



617 



under conditions whicli practically eliminate 

 surface erosion. Both canal and reservoir 

 mud, together with soil and subsoil, are fer- 

 mented with organic matter to be used as 

 fertilizers to an extent which would appear 

 to western nations impossible. Indeed it ap- 

 pears probable that as much labor and time 

 are spent in specific fertilization of the fields 

 as in seeding and harvesting the crops. 



While these people, so far as we can learn, 

 have never used rock phosphates or potash 

 salts taken from mines, as western nations are 

 doing in recent years, they have in effect done 

 so to a remarkable extent through their home 

 manufacture with their compost methods. So 

 far as we could discover they have nowhere 

 developed or applied systems of tillage looking 

 specifically toward physical amelioration, as 

 such, for their soils but they have practised 

 the culture of legumes as a source of nitrogen 

 very systematically, persistently and exten- 

 sively. Feed and water the crops is written 

 on every field in China and Japan. Japan is 

 now beginning to import notable amounts of 

 commercial fertilizers and during the years 

 1906 to 1908 the total import of all kinds 

 aggregated 1,427,658 tons, with a cash value 

 of $55,423,394 and all applied to about 21,000 

 square miles of tilled land, constituting a tax 

 of more than a dollar per capita for the entire 

 population, and this is paying for an addition 

 to an already enormously large yearly fer- 

 tilization. 



But the one factor which is probably equal 

 in importance to all others is the extreme per- 

 sonal attention and care bestowed upon the 

 crops, made possible and necessitated by the 

 dense population and increasingly smaller 

 holdings. But this has not and can not sup- 

 plant their supplemental irrigation and their 

 plant feeding except through a smaller annual 

 output. It must be this factor coupled with 

 the increasing larger return to the fields of 

 plant food which has given rise to the increase 

 in yield during recent years in this country 

 and in Europe, to which attention has been 

 called. It is clear that such increase may well 

 be coincident with a decreasing plant-food con- 

 tent in soils of the stronger type and for the 



simple reason that great care may augment 

 the rate of production of the plant-food con- 

 tent of film moisture for a time, with a de- 

 creasing content of the basal food elements. 

 That the oldest and most densely settled coun- 

 tries should show marked increase in yield is 

 to be expected, for here is where better care 

 pays best, where it is compelled and where it 

 is more readily made possible because of the 

 denser population. But it should not be ig- 

 nored that the countries named are those 

 which are largely importing feeding stuffs and 

 fertilizers which immediately or ultimately 

 find place in the soil, and that those who pur- 

 chase and apply these have faith that they are 

 indispensable adjuncts to better cultural meth- 

 ods, improved varieties and more sanitary 

 conditions. 



There were imported into the United King- 

 dom in 1885, 282,960 tons of oil cakes ; 64,387 

 tons of bones and fish; 25,258 tons of guano, 

 and 238,572 tons of mineral phosphates. In 

 addition, some 300,000 tons of Thomas slag 

 are manufactured annually and largely used 

 at home. During 1861-65 there was a mean 

 annual importation of 1,277,778 tons of 'grains 

 and beans, besides wheat. During 1901-05 

 importation had increased to an annual mean 

 of 4,641,204 tons. A mean of these values 

 may be taken, together with the fertilizers 

 named, as a low measure of the annual impor- 

 tation of plant-food substances into the United 

 Kingdom during the past twenty or thirty 

 years. 



As a rough approximation, it may be said 

 that 2,000 pounds of the products named will 

 contain : 



N P K 



lbs. lbs. lbs. 



Oil cakes 120 18.8 30 



Bones and fish 80 170 



Guano 70 170 



Mineral phosphates 250 



Thomas slag 160 



Grains and beans 50 8 12 



The arable lands of the United Kingdom 

 aggregate 19,528,000 acres and there are 28,- 

 267,000 acres of permanent pasture. 



On the basis of the amounts named the 



