Feb. J5, 1918 Humus in Mulched Basins 517 



however, to be due more to the humus added with the manure, than 

 to the greater " humification " of the manure over the alfalfa. 



When manure alone was used as mulch in basins the increase in hu- 

 mus was greater than when lime was added with the manure. 



In most cases when lime was added to alfalfa in basins greater increase 

 in the humus content occurred than when alfalfa alone was used. 



Blood, acid phosphate, bone meal, tankage, or sulphur did not show 

 any appreciable influence on the changes of humus content in mulched 

 basins. 



It was not evident that there was any appreciable accumulation of 

 humus in the lower depths of soil due to the leaching of humus from the 

 surface foot of soil. 



Thsre was no evident correlation between the amount of humus in the 

 soil in mulched basins and the amount of fruit on the trees. 



There was no evident effect of lime on orange production in these 

 experiments. 



Alfalfa and bean-straw mulch in basins on the heavier soil types 

 produced from 30 to 100 per cent more oranges per tree than manure 

 mulch. Manure mulch produced more oranges per tree than either 

 barley hay, sweet clover, bur clover, or pine shavings. These differ- 

 ences were obtained in the summer following the application of the 

 mulches in the preceding fall. 



Alfalfa mulch and manure mulch in basins on the lighter types of 

 soil produced no observable differences on fruit production of lemons 

 in the course of one year. This statement is based only on observation 

 and not on picking records. 



In all experiments so far conducted by this Office in the Riverside area, 

 the mulched-basin system on the heavier soil types has produced favora- 

 ble growth response in a few months. It usually takes longer to produce 

 appreciable response on the lighter soil types. 



It would appear directly from the work here reported, and indirectly 

 from work elsewhere reported that the degradation products from 

 freshly decomposing organic substances are more effective in orange 

 production than the amount of "humus" formed. And the value of a 

 given mulch does not necessarily depend upon its being a legume or 

 nonlegume. 



LITERATURE CITED 



(i) Briggs, L. J., Jensen, C. A. and McLane, J. W. 



1916. mottle-leaf of citrus trees in relation to soil conditions. In 

 Jour. Agr. Research, v. 6, no. 19, p. 721-739, 4 fig., 3 pi. (partly col.) 

 (2) 



1917. THE MLTLCHED-BASIN SYSTEM OF IRRIGATED CITRUS CLT^TURE AND ITS 

 BEARING ON THE CONTROL OF MOTTLE-LEAF. U. S. Dept. Agf. Bul. 499, 



31 p., I pi. 



