MULCHED-BASIN" SYSTEM OP IRRIGATED CITRUS CULTURE. 21 



Table IX. — Relative yields of oranges with different mulching materials in 



the basins. 



Mulching material. 



Alfalfa hay. . . 

 Bean straw . . 



Manure 



Barley hay... 

 Sweet clover . 

 Bur clover. .. 

 Pine shavings 



Number 

 of trees. 



Yield in 1916. 



Average 

 number 



of 

 oranges 

 per tree. 



550 

 463 

 358 

 280 

 314 

 302 

 224 



Corrected 

 on basis 

 of pre- 

 vious 

 perform- 

 ance of 

 trees. 



532 

 400 

 358 

 313 

 305 

 300 

 217 



Percent- 

 age of 



iriKin 



yield 



of whole 



block. 



150 

 130 

 101 



It is evident from Table IX that the mulching materials tested 

 differ greatly in value. The highest yield of fruit was obtained when 

 alfalfa was used as a mulch, while the bean straw and manure rank 

 next. The quantity of bean straw used, however, was not sufficient 

 to make an effective mulch, and it seems probable that alfalfa and 

 bean straw are of approximately equal value for mulching purposes. 

 The other legumes were much less beneficial than alfalfa and bean 

 straw. The lowest yield was obtained where pine shavings were 

 employed as a mulch. This material effectively protected the basins 

 from evaporation, so that the beneficial action of the other mulching 

 material is clearly attributable to the organic products from the de- 

 composing mulch which are carried into the soil with the irrigation 

 water. 



The average number of oranges on the trees basined and mulched 

 with alfalfa hay was 8 per cent greater than the average yield from 

 these same trees during the preceding six years under furrow irriga- 

 tion and clean cultivation. The other treatments all show a falling 

 off in yield compared with the average yield of the preceding six 

 years. Up to the time the basins were established, the trees had been 

 irrigated by means of furrows between the tree rows. When the 

 basins were established under the trees, the irrigation between the 

 tree rows was discontinued. The excavations of the basins to a 

 depth of 6 to 8 inches necessarily destroyed some of the small feed- 

 ing roots, and this fact, combined with the discontinuance of the 

 irrigation between the tree rows, forced the trees to establish a new 

 root system during the time that the fruit buds of the 1916 crop were 

 being developed. A decrease in yield accompanied in most instances 

 the redistribution of the root system, and this fact emphasizes the 

 desirability of a gradual transition to the basin system if the entire 

 surface is not basined. Irrigation and cultivation between the basins 

 for the first year following the installation of the basins would help 



