14 



lil l.l.KTIX 4!>i), U. S. DEPARTMENT OF AGRICULTURE. 



basins to supply mulching material. The basins in this grove were 

 small and "were separated in the tree row by spaces about 4 feet in 

 width. These spaces between the basins were bare and unirrigated, 

 the usual practice. The results of the moisture determinations pre- 

 sented in Table VII show no lateral movement of soil moisture from 

 the basins into these spaces during irrigation. 



Table VII. — Available -so// moisture hefore and after irrigation in an orange 

 grove having alfalfa growing in the furrow rows at Redlands, Cal. 





Available moisture before 

 irrigation (percent). 



Available moisture after 

 irrigation (percent). 



Depth. 



In 

 basins. 



In 

 alfalfa 

 furrow 

 rows. 



Between 

 basins in 

 tree rows, 



about 2 

 feet from 



basins. 



In 

 basins. 



In 

 alfalfa 

 furrow 

 rows. 



Between 

 basins in 

 tree rows, 



about 2 

 feet from 



basins. 



First foot 



4.2 



4.8 

 5.1 

 4.3 



-1.4 



- .6 



.1 



.4 



0.9 

 1.8 

 2.1 

 2.9 



7.4 

 6.4 

 5.5 

 4.9 



4.9 



.8 



1.0 



1.9 



-0.7 



Second foot 



1.1 



Third foot 



2.4 



Fourth foot 



3.1 









4.6 



- .4 



1.9 



5.6 



2.2 



1.5 







SUMMER COVER CROPS IN ORANGE GROVES NOT PRACTICABLE 

 WITHOUT AN INCREASED WATER SUPPLY. 



The moisture conditions in the alfalfa furrow rows as shown in 

 Table VII are quite typical of conditions found in other orange 

 groves with alfalfa growing between the trees. In 1914, soil samples 

 were taken in three groves of this kind after irrigation, and the 

 moisture had penetrated only from 10 to 30 inches after a two or 

 three days' run of water. The large amount of water removed by 

 such crops and the bad effect on the orange trees of the competition 

 with the cover crop have already been mentioned in connection with 

 the experiments in the Victoria and Vivienda groves. With the 

 amount of water usually available for irrigation in these districts 

 (1 miner's inch to 5 acres), no summer cover crop of any kind can 

 be grown in citrus groves in the areas studied without causing dete- 

 rioration of the trees. Instances were found where summer crops, 

 such as buckwheat and sAveet clover, were grown quite regularly, 

 but in these cases there was plenty of water available for both trees 

 and cover crop. 



ORGANIC MULCHES MORE EFFECTIVE THAN SOIL MULCHES IN 

 CONSERVING WATER. 



Four cylindrical cans 24 inches high and 18 inches in diameter 

 were filled with soil from the Victoria grove on June 25. The soil in 

 the different cans was treated as follows: (1) Surface soil kept 



