42 HORTICULTURE, FORESTRY, FLORICULTURE 



therefore, that the owners of red land should be especially careful to 

 maintain a liberal supply of humus under all circumstances, and to 

 calculate upon this extra loss due to the presence of the iron. (Mo. 

 E. S. Cir. 22.) 



Making the Plant Food in the Soil Available. As is well 

 known, only a small portion of the plant food contained in any good 

 soil is at any one time available to growing crops. The processes 

 which render this plant food available are going on more or less 

 actively, practically all the time. The rate, however, at which this 

 food is made available to the growing tree will vary according to the 

 season and to the method of treating the soil. For example, during 

 an excessive wet season, when the soil is either water-logged or being 

 leached much of the time, there is unlocked in the soil a relatively 

 small amount of plant food, and much of that w r hich was already 

 made available is lost either temporarily or permanently through the 

 processes of leaching. This means that the soil should be watched 

 carefully the year following an excessively wet season. This is par- 

 ticularly true if the trees following such a season happen to set a 

 large crop of fruit. Then, during a very wet season, the soil solu- 

 tions are so diluted that the trees will actually find less plant food 

 and have greater difficulty in getting that which they do find. 



Likewise, in a very dry season the chemical and biological 

 changes are very much retarded, owing to the absence of moisture. 

 Nevertheless, it should be remembered that in such a season the move- 

 ment of soil moisture is upward from great depths, and large quan- 

 tities of moisture are brought to the surface and vaporized. The 

 plant food that had in wet seasons been carried beyond the depths of 

 the ordinary growing crop is brought by this upward movement of 

 the water to the surface and by the vaporization of the water depos- 

 ited there in a readily soluble form. This does not mean, however, 

 that the plants derive benefit from these salts during tne drouth, for 

 there is not sufficient moisture in the soil to make this possible. 

 Therefore, while a dry season does not favor the breaking down of 

 the plant food compounds in the surface soil, it does in fact favor 

 the accumulation of this soluble plant food in the surface soil, by 

 bringing it from great depths, and also by the limited amounts used 

 by the trees on account of the small fruit crop and the very sparse 

 growth they make in such an unfavorable season. 



Thus should there be expected following a very dry season an 

 extraordinary season of growth, and if by any treatment in that dry 

 season we can without permanent injury to the trees induce them to 

 set a good fruit crop the following year, it is very likely to prove ex- 

 ceedingly favorable for the development of this fruit. Not only are 

 the conditions likely to be favorable for the development of a fine 

 crop of fruit following a dry year, from the standpoint of an abun- 

 dance of plant food to mature a maximum crop, but from the stand- 

 point of a diminution of insect pests and a reduction of the prev- 

 alence of fungous diseases. 



In the ordinary season it is necessary for orchardists to put forth 

 some effort in order to unlock the plant food contained in this soil. 



