MULCHED-BASllsr SYSTEM OP IRRIGATED CITRUS ci;i.Ti;i:|.;. 5 



Prof. Fawcett had returned from a iriji to Florida and Cuba and brought bad 

 reports of having seen very marked recovery ..of trees, apparently similarly 

 affected, brought about by heavy mulch, we selected six rows 49 trees long 

 through the very center of our worst affected area. We first plowed l In- ground 

 and, after running three large furrows for irrigation, covered three of Hm-si- 

 rows, spaces and all, with manure and three of them with bean straw to a depth 

 of 4 to 6 inches. From the road in the valley below looking up toward fin- liill 

 slope where this orchard lies one can see these six rows standing out in contrast 

 like a belt of green ribbon across a yellow background. It is remarkable, and 

 all in nine months. Later observations from the near-by hills reveal the fact 

 that the small tract mulched over two years ago is also darker green than the 

 surrounding orchard, though the contrast is not so great, because it lay among 

 healthy trees and was itself a group of normal trees. 1 



While surface mulching of orchard trees in humid regions with 

 organic material has long been practiced on a small scale, it has not, 

 in the United States at least, been followed to any great extent. The 

 results of recently reported investigations in Pennsylvania by Stew- 

 art 2 indicate, however, that surface mulches of strawy manure, alfalfa 

 hay, or other organic material may be used with advantage and profit 

 in the culture of apples on a commercial scale. Stewart summarizes 

 his investigations in part as follows: 



In general the mulch treatment, reinforced by outside materials, has been 

 most efficient in improving the yield, growth, and average size of fruit in 

 orchards up to about 20 years of age. In older orchards it has been surpassed 

 slightly by tillage and cover crops, unless accompanied by adequate fertilization. 

 It has also been most efficient in conserving moisture in all cases that have been 

 determined. 



The crop value of the present mulch has averaged 76^ bushels per acre 

 annually in the seven normal comparisons available. Its annual gain over 

 tillage and cover crops has averaged 15.S bushels per acre in the same experi- 

 ments. The mulch is therefore a valuable treatment when properly managed 

 and when mulching materials are available at not over $7 per ton, unless 

 tillage is not practicable. All mulches should be kept at least a foot away from 

 the tree trunks, and a greater distance is desirable as the trees enlarge. 



Fawcett, 3 of the California Citrus Experiment Station, has re- 

 cently made the following observations regarding the use of organic 

 mulches in citrus groves in Cuba, where the distribution of the rain- 

 fall is similar to that in Florida, the greater part occurring during 

 the summer months: 



At Herradura, Prof. F. S. Earle showed the writer a grapefruit grove on clay- 

 loam soil underlain with stiff clay, where part of the grove had been mulched 



1 As this bulletin is going to press Mr. Culbertson informs the writers that the six 

 rows of mulched trees yielded 36 per cent more fruit in 1916 than the adjacent six rows 

 of unmulched trees, although at the beginning of the experiment the rows selected for 

 mulching were the lowest yielding rows in the block. At the present time (winter of 

 1916-17), however, the mulched rows are again becoming yellow, so that the future 

 success of the surface mulch is still uncertain. 



2 Stewart, J. P. Cultural methods in bearing orchards. Penn. Agr. Exp. Sta. Bui. 141, 

 28 p., 4 fig. 1916. 



3 Fawcett, H. S. A comparison of some citrus conditions in Florida, Cuba, and 

 California. In Mo. Bui. Cal. State Com. Hort., v. 5, No. 9, p. 321-337, fig. 10S-117. 

 1916. 



