66 BOARD OF AGRICULTURE. 



be applied as a top-dressing to grass-lands under the same 

 conditions as barnjard-manures, as tlie two forms of plant- 

 nutriment exist in the agents under widel}' different circum- 

 stances. Manures, or stable-dung, must undergo some 

 important chemical changes before the active principles are 

 formed, or before they are fitted for plant assimilation: the 

 nitrogenous part, so important in the growth of grasses, is 

 not really formed in manure. The elements must be grouped 

 differently, and new combinations produced, and thus the 

 factor of time comes in to be considered. Ammonia as such, 

 although it holds the nitrogen, cannot be assimilated by 

 plants : in fact, it is destructive to plant-life when brought in 

 contact with them in concentrated form. Horse-manure 

 in its active state of change, and charged with free ammonia, 

 Avill destroy grass, if spread upon it in a still, cloudy day. 

 With chemical salts holding nitrogen in fixed condition, 

 • either as sulphates, nitrates, or carbonates, the case is dif- 

 ferent : these are soluble forms, and readily take the next 

 step which fits them to enter the structure of plants. As 

 regards the other imjDortant elements of food, — the phos- 

 phoric acid and the potash, — similar conclusions may be 

 entertained. 



It is obvious, then, that, in employing the different combi- 

 nations for. top-dressings, we must be guided by an intelligent 

 understanding of the nature of the agents ; and this applies 

 to time of application as well as to methods. I have had 

 considerable experience in this matter of top-dressing grass- 

 lands, and therefore feel competent to advise upon the sub- 

 ject. In the use of stable-dung we say. Apply it rather late 

 in the autumn, but not too late ; that is, do not wait until 

 the ground freezes, but do it about a month before the usual 

 time for the advent of severe frosts. If applied too early, as 

 in August or September, in the northern parts of the country 

 ■it dries hard in the sun, and is not so readily acted upon by 

 frosts ; and, besides, it sinks deep into the grass, and is there- 

 fore not so well distributed as it should be. The active 

 principles have time enough to undergo chemical change 

 from October to April or May of the succeeding year. 



Concentrated fertilizers should not, under any ordinary 

 conditions, be applied in the autumn. The reason is, that, by 

 the rapidity of the change, the active elements of food are 



