Archive Nut, Prune and Olive Programs

Using Nemaguard seedlings growing in sand, we conducted a series of experiments comparing different zinc formulations. The seedlings were grown with a nutrient solution containing no zinc until deficiency symptoms were observed.

We have conducted research to show that foliar urea sprays in the fall can contribute to the total nitrogen needs of a peach or nectarine tree.

Zinc deficiency is common in peach, plum and nectarine orchards in the San Joaquin Valley. Generally, it is a rootstock problem as typical orchard soils are not deficient, but Nemaguard is a poor forager for this nutrient. Some other rootstocks do not exhibit the same problem.

We have several year's experience with a dormant season procedure for sampling shoots. There are still many details to work out, but it appears to show promise for some nutrients.

Phosphorus is an important nutrient in all plants as it is required for membranes, energy molecules and nucleic acids. However, it is seldom deficient in stone fruit trees in California.

Sulfur deficiency has never been documented in California stone fruit orchards. This is probably because S is found in many fertilizers and is abundant in most soils. In addition, it is found in the atmosphere and is carried into the soil by rain.

Copper deficiency is rare in California stone fruit orchards but has been observed in plums growing on Nemaguard rootstock. Symptoms include shoot dieback and formation of small, chlorotic and malformed young leaves. Rough bark accompanied by gumming also occurs.

Both these nutrients are needed in very small amounts in fruit trees. Deficiencies have never been documented in the field, so leaf threshold levels have not been established. When we have analyzed leaves for Mo, values have generally been between 0.04 and 0.30 ppm.

Chlorine is needed in very small amounts in fruit trees, but is seldom deficient. The more serious problem with this element is when it is in excess, leading to salt toxicity. Peach, plum and nectarine are particularly sensitive to this disorder. Leaf levels need to be kept below 0.

Having peach trees in the lysimeter for nearly 20 years has allowed us to determine precise crop coefficients for orchards under different conditions. The graph on the right and chart below show average crop coefficients for mature peach trees.