MULCHED-BASIN SYSTEM OP IRRIGATED CTTRUS CULTURE. 7 



common division bank of two basins. 1 These square basins were 

 mulched with manure in 1913, and in 1914 they received another 

 mulching of manure (25 to 30 cubic feet per tree) and about 75 

 pounds of barley straw on top of the manure. In the summer of 

 1915, each basin received l-£ bales of damaged alfalfa hay. 



The experiment included three rows of 16 trees each, making 48 

 trees in all, or approximately one-half acre. The irrigation water 

 was applied by turning the water into the upper basin of each row 

 separately and allowing it to overflow into the next basin below, and 

 so down the entire row. This method of irrigation was found, 

 however, to be unsuitable to the deep sandy loam soil of this tract. 

 The upper basins were under water too long a time before the lower 

 basins were irrigated, and the water at the upper end of the row 

 penetrated the subsoil below the zone occupied by the principal feed- 

 ing roots of the trees, resulting in waste. In order to exercise both 

 control and economy of irrigation water, it is necessary to run a 

 furrow down the entire length of the row just outside the basins, so 

 that each basin can be irrigated separately. This procedure was 

 subsequently adopted and is the one usually followed by growers who 

 are installing mulched basins on a commercial scale. 



MOISTURE DETERMINATIONS IN THE SUNNY MOUNTAIN GROVE. 



At intervals during 1914 duplicate soil samples were taken to a 

 depth of 7 feet in two basins near the upper end of the middle row 

 of basins, and similar samples were taken in two basins near the 

 lower end of the same row, the two outside basined rows being consid- 

 ered as guard rows. Similarly, duplicate samples were taken in the 

 furrow-irrigated part of the grove two tree rows distant from the 

 basined tract, the trees selected for sampling being opposite the 

 basined trees sampled. 



In Table I are given the results of moisture determinations made 

 in this experimental tract during the seasons of 1914 and 1915. In 

 1914 the total moisture averaged about 3.7 per cent higher in the 

 basins than in the check. The moisture available for growth in the 

 first 3 feet of soil in the basins also averaged 3.8 per cent higher than 

 in the check, being an equivalent of approximately 4 miner's inches 

 per acre flowing 24 hours. It will also be noticed (sec. C) that while 

 the first 3 feet of soil under the basins never dried down to the 

 wilting coefficient, the first 3 feet of soil in the check dried out below 

 that percentage three times during the two years, and at four other 



1 While the mulched basin was developed independently by the writers, we have 

 since learned that Mr. J. R. Hodges installed several mulched basins in a grove at 

 Covina, Cal., at an earlier date (1911). So far as the writers know, this was the 

 first use of the system. 



