Using Mid-summer Leaf Samples to Guide Fertilizer Decisions: How I Apply Potassium

Within our operation, applications of potassium occur throughout the season. Soils on the farm vary, and the lowest CEC identified was around 10 meq/100g. We utilize a 12-0-4 liquid fertilizer as our primary material for fertigation. We target 40-50% of our budget using this material.  In the fall, we will apply remaining budget as a granular potassium sulfate. This material is applied as a targeted broadcast, in which the material is spread over a 5´/1.5m band between the drip irrigation lines of the tree. Within our soil samples, we are targeting >150ppm or 5% exchangeable potassium, but soils tend to be less than that. At the time of orchard development, low levels are generally present within the soil, so potassium is applied in years 1 and 2 at around 60 kg of K₂O/ha, and this is increased in years 3 to account for tree crop. Afterwards, applications match crop removal.Although we tend to rely on potassium sulfate, we do use other sources. Foliar sprays are made with potassium nitrate, but generally at low, somewhat insignificant levels (5-10 lbs/acre or 5-10 kg/ha of KNO₃). Potassium chloride is utilized as a proportion of our budget (~15%) within the blend. This material is utilized due to the amount of rain received which will leach the chloride out of the rootzone. This product may be substituted with potassium sulfate if winter rains are inadequate. Additionally, we utilize composts and other materials on an as available/affordable basis. This includes almond hulls and other biomass which we incorporate at very high rates (>10 tons/ha) several months prior to planting the orchard.