accumulates, the ammonia is prevented from escap- 

 ing. The gypsum must be moist for this use to be 

 effective. 



If, however, it is not desired to get the benefits of 

 plant food quickly, the manure had better be applied 

 fresh and incorporated with the soil at once. Decom- 

 position may be slower in such cases, but loss of 

 ammonia is surely prevented and a much better 

 mulch obtained. 



" Humus is not only the principal source of nitro- 

 gen in soils, but it influences to a marked extent the 

 available potash and phosphoric acid. Humus- 

 forming materials, like green manures and yard 

 manure, have the power, when they decompose in 

 the soil, of combining with the potash and phosphoric 

 acid of the soil and thus converting them into forms 

 which are readily utilized by the plants." (From 

 Experiment Station Work, V. of the U. S. Department 

 of Agriculture. ) 



GREEN MANURING. 



The object of sowing the leguminous, or pod- 

 bearing plants is four-fold. 



1st. To obtain the nitrogen which they produce 

 by their growth. 



2d. To set free unavailable plant food by the 

 action of their roots. 



3d. To lighten the soil by plowing them under 

 while green. The capacity of soils for absorbing and 

 retaining moisture is thus increased, part of the cost 



41 



