30 BULLETIN 499, U. S. DEPARTMENT OF AGRICULTURE. 



treatment in 3 months, while basined trees on light 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 soils. 



The set of fruit was very light throughout the Riverside district 

 in 1915, owing apparently to cold weather following the bloom. In 

 the Sunn}' 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 material with the soil, 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 



