436 IRRIGATION FARMING. 



two weeks after receiving the most thorough surface 

 irrigation. The trees suffer in consequence, and the 

 size and quality of the fruit is seriously impaired. 

 The diflficulty has been overcome in a measure by 

 breaking the hard-pan crust with a subsoil plow, such 

 as is shown in Fig. no, running the plow one or two 

 rounds, midway between the rows of trees as described 

 in the chapter on orchards. 



Frank L. Palmer, of North Pomona, California, 

 once tried the experiment of tearing up some of this 

 hard-pan by furrowing with a ten-inch turning plow in 

 the middle of July. He plowed eight rows in this 

 manner and turned up large chunks of hard-pan, which, 

 of course, were difficult to subdue, but he finally suc- 

 ceeded in pulverizing them and getting the surface 

 into tolerable condition again. Notwithstanding this 

 the soil began to run together after the first irrigation, 

 and the trouble seemed to be as pronounced as ever. 



Analysis of this formation showed that while it 

 contained no excess of lime or of carbonates, it had 

 four per cent, of aluminum hydrates, and this consti- 

 tuted the bulk of the cementing material. It was sub- 

 sequently ascertained that the water used in irrigating 

 this particular orchard carried excess quantities of 

 lime in solution, and this naturally added to the diffi- 

 culties experienced when applied to the land under the 

 scorching influence of the sun. This perplexing prob- 

 lem is in facft nothing new in Southern California, for 

 the chronicles tell us that as far back as loo years ago 

 a similar condition existed near San Gabriel. The 

 lands formerly cultivated by the padres about the old 

 Spanish missions were irrigated from ditches, which 



