FERTILIZERS AND MANURES FOR THE ORCHARD 207 



which of course comphcates the matter but the results after 

 eight years may be summarized as follows: "Exact records 

 of yields and measurements of growth have been taken since 

 the experiment was begun. No differences that could be 

 attributed to the additional nitrogen (or other ingredients) 

 in the fertilizer have been noticed." ^ 



177. The Oregon experiments. — An interesting example 

 of the influence of commercial fertilizers on a cultivated 

 orchard of bearing apple trees is shown by the work of 

 Lewis and Brown in Oregon.- The soils were exhausted 

 by continual clean cultivation without the use of green- 

 crops to maintain the supply of organic matter. Neither was 

 irrigation practiced in order to supply the necessary moisture. 

 As a result, the soils "lacked water-holding capacity, they 

 baked or puddled early, and on hillsides were given to ero- 

 sion." Two years' work demonstrated that no response of 

 a practical nature could be expected from the use of potash 

 or phosphoric acid, but when nitrogen was supplied the ef- 

 fect was immediate. This would seem to be a special case 

 in which the soil had reached the point of exhaustion of 

 available nitrogen, and hence would no longer support the 

 trees satisfactorily. Even though all these soils were cul- 

 tivated frequently and part of them continually, the appli- 

 cation of nitrogenous fertilizer gave as quick returns as 

 when it is added to a run-down sodded orchard. The appar- 

 ent exception here to the general premise in this text is prob- 

 ably largely explained by the authors of the work as follows: 

 "We are all familiar with the fact that shade crops induce 

 bacterial action and by liberating nitrogen, stimulate tree 

 growth. There are many evidences to show that alfalfa, 

 left pennanently in the orchard, does not stimulate wood 

 growth as rapidly as where placed in a shorter rotation with 



1 Me. Agr. Exp. Sta. Bull. 236, 260. 



2 Rept. 1916. Hood River Branch Exp. Sta., p. 37. 



