Which Fertilizer to Use on My Fruit Trees and Grapes?

Q. I wonder what fertilizer you recommend for my fruit trees? The young trees I recently planted in my small orchard are: plum, peach, apricot, lemon, pomegranate, plus several table grape vines.

A. Lisa. Rather than just tell you what I would use, let me give you a little background on fertilizer selection.

To select the right fertilizer I am supposed to tell you that you should test your soil for nutrients first and then make your selection of fertilizer based upon the test results. That's the right answer but it's not always the most cost effective thing to do if you will have only a few trees. The soil test would cost about $75. You can buy a lot of fertilizer for $75. It makes sense to do this if you are a farmer and spending thousands of dollars on fertilizers and you want to get the most "bang for your buck" but for homeowners it doesn't make a lot of sense.

Mineral or Conventional Fertilizers

A reader applied wood chips around the base of the tree covering the area outlined by the tree canopy. Bender board is used in a circle to keep the wood chips away from the tree trunk while it is small.I suggest the wood chips should be at least 4 inches deep covering the soil around the fruit tree.

Most of our soils will support the use of mineral fertilizers from a bag for many years if we have the soil covered with wood chips that slowly decompose in the irrigated areas. If the fruit trees are surrounded by rock on the surface of the soil than the proper fertilizer selection becomes more critical.

Let's say you have your fruit trees surrounded by woodchips. Fruit trees planted in lawns could be put into this category as well. Just be careful of irrigating the 2 together because they have different water requirements. If the trees are surrounded by rock instead of woodchips, they are growing in the soil that's more similar to hydroponics. Fertilizer selection is more critical when fruit trees are surrounded by rock.

Numbers on the Bag of Fertilizer

Mineral fertilizers have 3 numbers on the bag. If the fruit trees are less than 3 years old, use a fertilizer that has the first and third numbers highest. The middle number, phosphorus, can be lower than the other 2. If the fruit trees are starting to produce fruit, use a fertilizer that has all 3 numbers the same value. Use this fertilizer only once at the beginning of the growing season and apply it about 2 weeks before the flowers appear. In Las Vegas, this would be about the middle of January to 1 February. For grapes, this would be about a month later.

Bag of conventional fertilizer called to Flower Power with 3 numbers denoting nitrogen, phosphorus and potassium

Application of fertilizer is frequent enough unless you have very sandy soils. But if you decide to make a second application, and the trees are surrounded by wood chips that are decomposing, only apply a high nitrogen fertilizer. This would be a fertilizer that has only the first number on the bag and the other 2 are zeros.

Another mineral or conventional fertilizer that contains only nitrogen as a plant nutrient source. This type of fertilizer should be applied less often and in smaller amounts because it doesn't last long in the soil.

Phosphorus

Phosphorus, the middle number on the fertilizer bag, sticks in the soil a lot longer than the other 2. Phosphorus is the only one of the 3 listed on the bag that can create some problems in the future if this mineral is continuously applied, over and over. This is the reason I recommend that people have 2 mineral fertilizers on hand. One fertilizer high in phosphorus, the middle number. And the other one high in nitrogen, the first number. The last number, potassium, should be as high as possible in both fertilizers. Potassium is a little bit more difficult to find in bags of fertilizers.

Compost As a Fertilizer Substitute

When you use a rich compost, it has all of the nutrients present. It is applied in a circle around the tree, about a foot away from the trunk or more, and watered, or lightly dug, into the soil. Rich compost is a very nice fertilizer and gently releases the nutrients to the plants over a long period of time. It is really my favorite to use but a good compost rich in nutrients is hard to find. 

When adding compost as a fertilizer, use a rich compost and keep it away from the trunk of the fruit tree at least 12 inches away.

Viragrow in North Las Vegas is the only place I know in Las Vegas that carries a rich compost like this. It is applied as a substitute to the first of fertilizer application. A second application is never needed and may even extend into the second growing year if enough is applied.