30 BULLETIN 499, U. S. DEPARTMENT OF AGRICULTURE. 
treatment in 3 months, while basined trees on hght soils required 
from 6 to 12 months to show a growth superior to that obtained with 
furrow irrigation and clean cultivation. The mulched basin is not — 
satisfactory on heavy gumbo souls. 
The set of fruit was very light throughout the Riverside district 
in 1915, owing apparently to cold weather following the bloom. In 
the Sunny Mountain tract, where the mulched basins were first 
installed in 1913, the average number of oranges per tree on the 
check trees in 1915 was 116, while on the mulched-basin trees the 
average number of oranges per tree was 281, or two and one-half 
times as many as on the check trees. The quality of the fruit on the 
basined trees was also superior to that on the unbasined trees. In 
the Victoria tract in 1916 the alfalfa-mulched trees averaged 483 
oranges, the manure-mulched trees 242 oranges, and the check trees 
182 oranges. In the Eureka tract, where the mulched basins had 
been installed the preceding autumn, the alfalfa-mulched trees car- 
ried on the average 550 oranges, an increase of 33 oranges per tree 
over the average yield of these trees for the preceding six years. 
Experiments in this tract with other mulching materials showed a 
decrease in yield during the first season, due in part at least to the 
fact that the new root system below the basins was not established 
at the time the fruit buds were set. 
The new leaf growth on the basined trees was less mottled than 
the new growth on the unbasined trees after sufficient time had 
elapsed for the mulched-basin system to produce response in the 
tree growth. 
The new leaves on the basined trees were larger and darker in 
color and had a better texture than those on the unbasined trees, 
especially on heavy soil. 
The new growth of rootlets under the mulch in the basins was 
very much greater than in the check treatments, the soil in the 
basins being filled with rootlets to within about 2 inches of the 
surface. | 
Great numbers of earthworms were often found in the basins under 
the mulch, and their burrows honeycombed the entire soil mass. The 
worms help to incorporate the organic materia! with the soul, while 
their burrows facilitate the absorption of water in heavy soils. 
No soil crust of any kind has been found in the basins where the 
mulch completely covered the soil surface. A complete mulch must 
be maintained at all times, however, to prevent the surface from 
crusting. 
The experiments indicate that alfalfa and bean straw are superior 
to stable manure for mulching purposes. 
In the mulched basins the quantity of humus, as measured by the 
intensity of the color of the alkaline extract, increased markedly in 
