The taste of tree-ripened nutrient-dense fruit is one of the great joys in my life. I love a flavorful apple at the peak of ripeness, the sweetness of a juicy custard-textured persimmon, a glass of vibrant orange juice. Picking ripe wild blackberries was a late summer ritual in western Oregon where I grew up. Now I have a new ritual; every year I plant fruit trees.
Here on the Central Coast of California we are blessed with a climate that allows us to grow apples and avocados, citrus and plums, apricots and persimmons, pears and berries. We have just enough chill hours in the winter to grow apples and pears, but not the freezing weather that would kill citrus and avocados (although the 26 degree nights last winter did take their toll by severely trimming back our most frost sensitive lime and avocado trees).
Fruit trees and citrus are an excellent indicator of topsoil and subsoil deficiencies. Since we are growing in sandy, low CEC soil here at Rancho Reinheimer, I have become a connoisseur of mineral deficiency descriptions and photos, searching for the “silver bullet” that will cause my trees to look like those in the nearby commercial orchards. It is this futile search for the “silver bullet” that originally led me to the use of soil testing and mineral balancing, but that’s a different story.
The long and the short of it is, deficiencies can and do show up in similar ways for different types of plants. They are an interesting indicator of how minerals move or don’t move in the plant. The pH of the soil can also affect availability of certain nutrients in the soil and can prevent their uptake in the plant. For example, high pH (>7.5) can block the uptake of iron.
Many of the pictures of nutrient deficient plants shown below have been taken under laboratory conditions, where just one nutrient at a time was withheld. Insect damage or disease symptoms can also look like nutrient deficiencies! Or a plant may suffer from multiple deficiencies, adding to the confusion.
Any diagnosis of a nutrient deficiency should only be made on the basis of a tissue test – a test where leaves or other plant parts are tested for nutrient content (it is best to test a control “healthy” sample at the same time). The instructions for doing a tissue test are on the test labs’ web site.
The pictures below are categorized by nutrient with references at the bottom of the post.
Nitrogen is one of the major nutrients needed by plants — it is used to make chlorophyll — and it is one of the most difficult to find organic sources for. A deficiency can result in yellowing of older leaves first as nitrogen is translocated to new growth in the plant. Stunting of growth can also occur. Different types of plant exhibit different symptoms — not all plant turn yellow.
Sulfur deficiencies look a lot like nitrogen deficiencies however sulfur deficiency affects new growth first because sulfur does not translocate easily in the plant.
Phosphorus deficiency can occur in cool weather. Our young tomato plants seem to be especially susceptible in early spring. It is characterized by a red or purple cast on new leaves and poor, stunted growth.
Calcium aids in cell wall strength in the plant. When deficient it can contribute to blossom end rot in tomatoes and corky spots in apples.
Magnesium can be deficient in certain soils but certainly not in ours. As with all deficiencies, it is best to have the results of a soil test and tissue test in hand before treating the symptom.
Potassium deficiency is not usually a problem for organic growers who apply composted manure, since manure is a good source of available potassium. Potassium deficiency shows up in the edges of the leaves first.
Manganese deficiency produces a leaf yellowing similar to zinc deficiency where the veins of the leaves remain green while the part between the veins turns yellow.
Iron deficiency tends to occur in high pH soil, where the pH is higher than 7.0 or in soils that are severely imbalanced. Its symptoms appear as a yellowing of the leaves in a manner similar to zinc or manganese deficiency, usually with green veins remaining.
In the mineral world they say that calcium is the trucker (in that it moves all the other minerals) but boron is the truck driver. This is apparent in the pictures of boron deficient fruits and trees. Somewhere along the line the truck has gone off the road, resulting in strange shapes, hollow or hard cores and variable leaves.
Boron is mobile in the soil and subject to leaching.
Zinc is another element that becomes less available at higher pH’s. it can be the limiting factor is tree crops in the drier and more alkaline western US. Zinc deficiency causes a symptom called “little leaf” where new leafs are abnormally small and causes a yellowing of the leaf between the ribs, similar to manganese deficiency but with less smooth edges.
Copper compounds are often used in the orchard in organically approved sprays (and in conventional sprays) that are used to control fungal disease. It is immobile in the soil, so if copper sprays have been used in the past, it is worth doing a soil test to determine the amount of copper present. Because of its immobility, copper tends to build up and can reach toxic or at least unbalanced levels. However, some soils are deficient in copper. Before doing a soil application it is worth considering whether copper would not be better applied as a fungal disease preventative spray.
We’ve got a great example of zinc deficiency in all of our citrus, even the dark green valencia orange tree grows next to the garden, and has ready access to the benefits of water and fertilizer there. Our dry soils and high pH make this a common deficiency in California citrus orchards. Both soil and foliar applications of zinc sulfate should help. We’ll see…
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