For:
By: Daniel E. Mullins
Extension Horticulture Agent
Soil Fertilization vs. Leaf Feeding? No
Contest!
Our sandy
Gardeners apply fertilizer either by applying it to the soil or by using a soluble product, mixing it with water and spraying it on the leaves. By far, a soil application is the best way to deliver nutrients to plants. While teaching a class about vegetable production one of my co-workers made this statement: “Roots are for taking up water and minerals and leaves are for photosynthesis.” How true. I wish that I had thought of this brief way of communicating such an important point years ago.
The foliar application of some nutrients has its place, but it should not become the standard method. The idea with “leaf feeding” as it is sometimes called, is that the nutrients are immediately available so the plant response is faster. Response might be faster in some cases, but it is not as complete or as long lasting when compared to soil applied fertilizer.
Obviously, the function of roots and leaves is much different. Roots take up minerals and water from the soil where they are transported to the leaves. Using energy from the sun, photosynthesis converts these minerals to usable sugars. This food is then translocated back to other parts of the plant that needs it including stems, fruit and roots.
Leaf feeding on the other hand, has many limitations. First, to avoid foliar burn a relatively weak solution of fertilizer must be used. The product must then be absorbed before being washed off of leaves by irrigation or rain water. And, perhaps the biggest disadvantage is that leaves cannot assimilate all of the various nutrients as well as those absorbed by the roots.
Fertilizers used for soil application are available in several forms including dry granular, slow release pellets or soluble. It doesn’t matter to the plant in which form the nutrients are delivered, as long as they are present in the right ratio and amount.
Foliar applications could be best used to supplement the basic soil application. Iron chlorosis for example, can often be quickly corrected with a foliar spray of an iron solution instead of making a second fertilizer application to the soil. Leaf feeding can also be used to provide a quick, temporary green up of lawns, flowers and vegetables.
Question of the Week: I am
moving to
Answer: The northern Rhodendrons do not perform well here. The better adapted evergreen azaleas are also
in the Rhodendron genus and there are dozens of
cultivars from which to choose. You
might also consider trying one or more of the Rhodendrons
that are native to northern
Rhodendron austrinum, known as
the Florida Azalea produces yellow or orange flowers, flowers early and is
fragrant. The Flame Azalea, Rhodendron calendulaceum, is a
late flowering and deciduous, producing orange-red flowers with an orange
blotch. Rhodendron
canescens flowers early, producing fragrant, white to
deep pink blossoms. Rhododendron
chapmanii is the rarest species. Native
to the