INDIVIDUAL ELEMENTS 145 



unknown. However, certain proteins crystallize as potassium salts; 

 sinigrin is myronate of potash. Complex salts of calcium, magnesium 

 and potassium are not uncommon. Gum arable contains a calcium- 

 magnesium-potassium salt of arable acid. 



During the winter, potassium is stored in both the sap wood and bark 

 and in older branches than nitrogen or phosphorus. In the spring, it is 

 translocated and used in the development of new tissue, but preeminently 

 for fruit and then for leaves. Heavy crops reduce the potassium content 

 of the leaves and much more potassium goes into the fruit than is lost 

 with the leaves. In general wherever potassium is present in large 

 amounts as in seeds and in young tissue, calcium is present in small 

 quantities and wherever there Is a small amount of potassium, calcium Is 

 present in large amounts. 



The Demand and the Supply. — In one way or another the idea has 

 gained credence that fruit trees make heavy demands on the soil for 

 potash and consequently that potash is one of the most necessary in- 

 gredients in fertilizers for orchards. Indeed, so firmly has this Idea 

 become estabUshed that " Fertilize trees with nitrogen for wood growth 

 and with potash for fruit production" is a time-honored recommendation 

 In the literature of fruit growing. It has also been a rather general 

 opinion that potash mainly is responsible for the red coloration of fruits 

 and that consequently potash-carrying fertilizers are especially desirable 

 for Improving color. That this last idea is erroneous is shown by the 

 results of many carefully conducted Investigations of recent years, in- 

 vestigations that are reported In more detail later in this section. The 

 data in this chapter afford some idea of the approximate amounts of 

 potash that are required for usual tree growth and production. Though 

 these are considerable in comparison with the amounts required by 

 many farm crops, the enormous quantities of this element found within 

 reach of tree roots in most soils make the application of potash-carrying 

 fertilizers seem of doubtful promise, at least so far as supplying the plant 

 with larger quantities of this element is concerned. This statement is 

 supported by numerous experiments In which potash in different forms 

 has been applied to orchard trees apparently without positive results, 

 and also by soil investigations like those of Hopkins and Aumer,i°^ 

 showing that in 6 feet of soil covering an area of 1 square mile of the 

 Illinois corn belt there Is as much potash as is applied annually in fertil- 

 izers to all the farms of the United States. It is true that many orchard 

 soils are not so liberally supplied with potash as those of the Illinois corn 

 belt; nevertheless, so far as data are available, they indicate the presence 

 of quantities much in excess of probable requirements for many years, 

 if not for many generations. Beneficial results in greater vegetative 

 growth and Increased yields have been reported occasionally from the 

 application of potash-carrying fertilizers to orchard soils. The question 



