sept-oct-2020

IN YOUR ORCHARD pressure. A lower rate, in the range of five pounds per acre of zinc sulfate, applied in October can be more effective in getting zinc into the trees without damaging leaves. When tankmixing sodium borate (Solubor ® -type materials) and zinc sulfate, keep the solution pH below six with an organic acid material (Trifol ® , MixWell™, etc.) to avoid a low grade incompatibility that can reduce boron delivery to the trees, even though it doesn’t plug nozzles in my experience. What about fall nitrogen fertilization ? In my experience, soil applied fall nitrogen does not improve yield next year in orchards with good production and adequate leaf nitrogen levels in the summer leaf samples. However, especially following a big crop, it is a good idea to double check lab results from July leaf levels. If levels are less than 2.2 percent nitrogen (deficient) then a low rate of fall nitrogen (for example, 30 pounds of nitrogen per acre) may be considered. Why such a low rate if trees are low in nitrogen ? Flower bud differentiation has already occurred, so any nitrogen applied now simply goes to storage for next spring and even deficient trees have limited storage space. Potassium nutrition is a good example of where careful management can maximize return on input investment. Potassium primarily accumulates in the nuts, so its demand is driven by cropload. A big crop requires a lot of potassium, a light crop not so much. In a tight budget year, growers must choose how and when to apply potassium to keep orchards out of deficiency and within budget. The cost of the traditional maintenance rate of potassium fertilizer (for example, dry potassium sulfate at 400 to 500 pounds per acre), applied in the fall long before the new crop set is known, is as much as 10 percent of total cultural costs. This is a solid investment in good years, avoiding the risk of potassium deficiency that can limit yield the next year. In 2021, there might be a reduced rate of potassium application (250 pounds dry SOP per acre) could be enough to keep July 2021 leaf potassium at or above adequate levels. If using a lighter rate this fall, mark your calendar in May or early June of 2021 for a quick early leaf sample to make sure leaf potassium levels are solidly above the July adequate level (1.4 percent potassium). If leaf levels are lower than that, a small rate of fertigated potassium (40 to 50 pounds K 2 O per acre) should keep the orchard out of deficiency through harvest. Pest Management Practices Pest management practices in the fall include careful monitoring and preparing for future practices. Monitor leaves for shot hole and rust in late October. Plan to take a dormant spur/twig sample to look for scale and scab after mid-November. A dormant spray is effective in managing these pests but may not be needed. 3 6 A L M O N D F A C T S