FERTILIZERS 
We cannot determine to the exact pound the fertilizer requirements of 
trees because soils vary so much, both in composition and the ability to 
retain fertility. Your soil must have certain physical properties before 
the addition of commercial fertilizer is worthwhile. The most important 
of these are temperature, moisture and proper aeration of the soil. Root 
growth will take place at about 40° temperature minimum and contin- 
uing through the summer as long as sufficient moisture remains in the 
ground. During hot, dry seasons the trees stop growth. The addition of 
humus to the soil in the form of green cover crops, manure, or peat is 
very beneficial because the straw or perhaps peat in the soil holds mois- 
ture while it is decomposing. The bacteria which works in the decom- 
position of this material is making available plant food during the entire 
growing season as long as a certain degree of moisture is maintained so 
the bacteria can work. Because decomposition of humus in the soil is 
adding plant food during the growing season it is not possible by a 
soil test to tell exactly how much chemical fertilizer your trees may re- 
quire. However, if your trees are not performing as you think they 
should a soil test may detect a deficiency in your soil which may be 
easily remedied. 
Another point for consideration. The various elements in commercial 
fertilizers do not take the same length of time to penetrate to the same 
depth of soil. Nitrogen penetrates quickly. Phosphorus about an inch of 
soil a year and Potash about two inches a year on an average. Again 
penetration depends on soil composition. From this you can readily see 
it is important to apply the fertilizer at the approximate place where the 
roots of the trees are and where it can be used readily. The punch bar 
method of fertilizing trees which have become established several years 
is best. Holes should be punched about every square foot over the root 
feeding surface, which is generally ground surface to equal the spread 
