192 POMOLOGY 



cated for orchards (at the rate of about 150 pounds to the 

 acre) to release the potash in the soil and thus furnish 

 the trees with that element. Since potash is not often the 

 limiting factor, this practice is not of importance to the 

 orchardist. Some such reaction as the following is believed 

 to take place in the soil: 



NaCl -h KAlSiaOs = NaAlSisOg + KCl. 



168. Animal manures in the orchard. — In several of the 

 fertilizer experiments already cited, the value of manure for 

 the orchard has been shown. When it is used on a sodded 

 or mulched orchard, it not only furnishes plant-food but, 

 what is often quite as valuable, it conserves the moisture. 

 As a top dressing in a sod orchard it is slower acting, how- 

 ever, and on the whole less effective than nitrate of soda, 

 when nitrogen is badly needed. In a tilled orchard it is 

 valuable as a source of organic matter as well as of plant- 

 food. 



That the experimental results from its use are variable is 

 shown by results in two orchards which seemed similar.^ 

 In one was obtained an aiuiual cash gain to the acre for five 

 years of $20.75, while in another the gain was $110.75, or 

 $2.00 an acre less than the adjoining plot treated with ni- 

 trate of soda alone. Unfortunately, these data are not given 

 in terms of yield. 



From work conducted in Pennsylvania ^ • it is reported 

 that ''in ten similar experiments, the gains from stable ma- 

 nure in both tilled and unfilled treatments have averaged 

 79.3 bushels per acre annually, while those from commer- 

 cial fertilizer averaged 73.0 bushels. In five cases involving 

 tillage, however, the gains from the fertilizer have averaged 

 99.6 bushels per acre annually, while those from the manure 



1 Ohio Agr. Exp. Sta. Bull. 301. 1916. 



2 Penn. Agr. Exp. Sta. Bull. 141. 1916. 



