Question
Hello

I live in Sedona Az and we have many trees in our yard, junipers etc.

I heard there is a way to inject the trees, or the soil with  some nutrition (some of them have partially brownish , (not green anymore) leaves.  

I know nothing about it.  What kind, how much, how often?

Any ideas, please?

Thanks,   Gabe  

Answer
Mature trees seldom need to be fertilized. If growing in or near a lawn which is reguarily fertilized they surely get all the fertilizer they need.

Browning of leaves are not typical signs of lack of fertilizer. An overall yellowing of the leaves, but continued growth with smaller new leaves than the older leaves can be sign of nitrogen deficiency. Browning of leaves are probably due to some other problem: insect, disease, lack of water, etc. Fertilizing "sick or stressed" trees will only make it worse.

Normally you inject fertilizer into the soil by digging equally spaced holes 6" deep with a drill in circles in a band extending 50% inside and 50% outside the drip line (canopy) of the trees. These holes are space 4-6" around. E.g. a canopy which is 5' beyond the trunk should be fertilized in a band start 2.5' from the tree trunk extending in a circle another 2.5' beyond the drip line (50% inside/50% outside the canopy). You would start by drilling holes every 6" in circles and moving your way in. In the above example, the outer ring would contain as much as 120 holes, the next ring (just inside) 100 holes, etc. Then fertilizer would be surface applied and brushed into the holes and the holes filled with topsoil/potting soil and watered.

The reason for injection as opposed to simply broadcasting fertilizer on top can be due to desire not to fertilize grass at this time, and make some nutrients, such as phosphorus and calcium which are not highly mobile in soil, directly available to the roots. However, more often than not, broadcasting (e.g. surface application) of fertilizer under and just beyond the canopy is adequate. If you fertilize your lawn already, chances are that the trees get as much fertilizer as they could every want.

I would check out the possibility of disease, insects and/or watering patterns. Junipers can be cut back to re-generate green growth, but make sure you deal with insect/disease first. An arborist is a good place to start.