722 EXPERIMENT STATION RECORD. [Vol.38 



produced four months after harvest to account for approximately 50 per cent 

 of the nitrogen added in the material turned under. From the standpoint of 

 the amount of available plant food, it is desirable that sweet clover, to be used 

 as a green manure, should be grown for at least four months. 



" The measurement of nitrate formation in pot experiments is subject to a 

 large probable error. This fact is a real objection to the method as a quanti- 

 tative measure of rate of decay." 



A bibliography of 22 -titles is appended. 



Composition of fallen leaves of forest trees and their quantities, S. Mobiya 

 {Extracts from Bui. Forest Expt. Sta., Tokyo, 1915, pp. 28-33; ahs. in Chem. 

 Abs., 11 {1917), No. 10, p. 1513). — To ascertain the manurial value of fallen 

 leaves of forest trees the fallen leaves of sugi {Cryptameria japonica), akamatsu 

 {Pinus densiflora), kuromatsu {Pinus thunbergii) , kunugi {Querctis serrata), 

 konara {Quercus glanclulifera) , and shirakashi {Qucrcics vibrayana) were col- 

 lected and analyzed. 



" The most important ingredient of fallen leaves is no doubt nitrogen. 

 Among conifers, the sugi leaves are richest in nitrogen, containing 0.972 per 

 cent, or about 1 per cent of the air-dried substance. Sugi is followed by 

 akamatsu, showing a percentage of 0.885, and kuromatsu, of 0.855. Broad 

 leaves are generally richer in nitrogen than needle leaves, those of kunugi 

 containing 1.116 per cent, shirakashi 1, and konara 0.945. 



" Broad-leaved trees have a larger proportion of ash in their leaves than 

 conifers. Among conifers, sugi, however, is relatively rich in ash, containing 6.1 

 per cent of the air-dried substance, which is three times that of the ash content 

 of akamatsu or kuromatsu. Among broad-leaved trees, kunugi has an ash con- 

 tent of 3.55 per cent, while konara contains nearly twice as much as the preced- 

 ing, and shirakashi has a still larger quantity, the content being 9.12 per cent. 



" Taking the three important ash ingredients known as phosphoric acid, 

 potash, and lime among the fallen leaves of the six aforesaid trees, sugi leaves 

 are richest in phosphoric acid and lime. Its richness in lime is particularly 

 noteworthy, as it contains 2.999 per cent of the air-dried substance, or 49.164 

 per cent of the total ash. Phosphoric acid, too, is found in considerable amount 

 in sugi leaves. Akamatsu and kuromatsu leaves . . . are rich in phosphoric 

 acid, being not inferior to those of broad-leaved trees, although they are poor 

 in potash content. The content of silica in kuromatsu is richer than that in 

 akamatsu, and to this is due the difference in the total ash content of the two 

 pines, though there is no particular difference in other ingredients of the ash. 

 Further, among broad-leaved trees, shirakashi and konara are rich in ash 

 content owing to the large amount of silica, while phosphoric acid and lime 

 are found almost in the same quantity as in other oaks such as kunugi. 

 Shirakashi is further characterized by the rich content of potash." 



With the object of determining the difference in the composition of fresh 

 fallen leaves and well-rotted ones, samples were taken from beds of well-rotted 

 leaves in the spots where fallen leaves were collected. It was found that 

 " well-rotted leaves a-re richer in nitrogen than fresh fallen leaves. Since 

 well-rotted leaves of akamatsu and kunugi contain 1.5 per cent of nitrogen in 

 round numbers, they both have a certain manurial value owing to their nitrog- 

 enous content. . . . Compared with freshly collected leaves, the silica, mag- 

 nesia, and oxid of iron contained in the ash of well-rotted leaves are remarkably 

 large in quantity. Phosphoric acid, potash, and lime are, however, gradually 

 washed away and decrease with the lapse of years." 



Studies of the soils of sugi, akamatsu, and kunugi woods showed them to 

 differ considerably in composition, " This is chiefly due to the difference of tree 



