144 Appendix. 



usual summer temperatures are very favorable, and it is a matter of common 

 observation how rapidly vegetable remains in the soil disappear during the 

 hot months. Well drained, porous soils are always the warmest. 



The third requirement I spoke of is moisture. Too much, indeed, as in 

 the case of the peat bog, is injurious by cutting off oxygen ; but the entire 

 lack of it is just as fatal, for no bacteria are active without the presence of 

 moisture. Keeping an abundance of humus in the soil is one of the best ways 

 of insuring the proper amount of moisture (indeed, this is the most valuable 

 feature of humus — more important than any fertility it adds to the soil) which 

 is also further increased by mulching. The amount of moisture most favor- 

 able to the growth of trees and crops is in a general way most suitable for the 

 bacteria. 



Before leaving this subject I ought also to mention the chemical composi- 

 tion of the soil as one of the tilings influencing bacterial welfare. A soil witli 

 much free acid in it is decidedly unhealthy for these organisms ; thus a sour 

 muck bed, even when properly drained, often refuses to decompose into good 

 loam until its acidity is neutralized by the application of lime. Of course 

 fresh lime actively attacks and breaks down vegetable matter, but' it soon 

 becomes slacked when added to the soil, and its active caustic properties dis- 

 appear. If added in excess it hinders or destroys bacterial action, and also 

 sets free nitrogen in the form of ammonia so rapidly that it is apt to escape 

 into the air and be lost. Its action after slacking becomes similar to that of 

 laud plaster, which has long been known as beneficial, though no one has been 

 able to assign just the reason ; but we may now set it down as more than likely 

 th.it its eSiciency has been due to its pronounced effects in aiding nitrification. 

 A slightly alkaline soil is most favorable for the process, and in soils derived 

 from limestone, we rarely find nitrates deficient. When we turn a cover crop 

 under, then, to supply nitrogen to our land, we consign it to the care of the 

 nitrifying bacteria, different groups of which convert the protein in it suc- 

 cessively into ammonia, nitrites and nitrates ; and to enable them to do this 

 effectively for us, we must manage the land so that they will have the proper 

 amount of air. warmth and moisture, together with a siutable chemical condi- 

 tion of the soil. 



Besides nitrogen, the legumes and other cover crops also contain potash 

 and phosphorus, but the last two are never added to the soil when the crop is 

 turned under, as the nitrogen of the legumes was, but are simply returned. 

 In spite of this, the soil is benefitted by the process, for the salts have been 

 worked over — digested, if you please — by the crop, and made more available 

 while its roots have penetrated several feet into the ground and pumped up 

 to the surface much nourishing material, which on the death of the plant is 

 set free in the surface foot of the soil, just where the trees can reach it most 

 easily. Certain crops, as turnips and rape, are particularly rich in potash 

 salts, and may be termed the "potash-gatherers," just as legumes are known 

 as "nitrogen-gatherers." This is generally a better and always a cheaper 

 way of applying potash than buying it, in the form of kainit or muriate of 

 potash. 



Other kinds of crops, such as oats, barley, rye or millet, contain no one 

 element in excess, but may be considered simply all-around fertilizers. If, 

 then, you have a soil requiring nitrogen, the legumes will serve you ; or if rich 

 enough in that, but lacking potash, turnips or rape ; and if you especially need 

 neither, but still seek the advantage of a cover crop, oats or rye. And what 

 are these advantages? The cover crop provides plenty of humus, which pro- 

 motes nitrification by making the ground more porous and airy, retaining 

 moisture in dry weather and helping drainage in wet ; takes up the nitrates 

 and other soluble foods which would leach away in late summer and fall 

 after the trees have stopped growing ; checks the growth of the trees in the 

 fall and causes them to ripen their wood, by using up the moitsure, (and to a 

 less extent, the food) ; covers the ground in the winter so as to prevent deep 



