Over the past few weeks, I have attended a few events that discussed the application timings of nitrogen. The results that were discussed at these events were based on an extensive five year study conducted by the University of California at a trial located in Kern County.One of the many findings of this study included the development of a nitrogen application schedule that maintains crop productivity. From this trial, the researchers have determined that 80% of the nitrogen should be applied before the completion of kernel fill (mid-June), while the remaining 20% should be applied in the post harvest. In the study, the researchers applied the spring nitrogen doses beginning in mid-February prior to bloom, and continued monthly until mid-May. They roughly followed a 10%-25%-25%-20% application schedule. The question remaining, especially with impending groundwater and nitrate regulations, is this applicable to all parts of California? The short answer is “Of course not,” as differing climates and soils create different challenges for growing almond efficiently. For example, in Merced County, we receive an average of 10-12 inches of rain and have some areas of very sandy soils. This is in contrast to the trial’s location in Kern County, which receives 6 inches of annual rainfall and is located on a sandy loam soil. Practices of nitrogen application, therefore, will vary by location – especially the timing of the first application. In a previous entry, I wrote about the movement of nitrate and the rationale for applying after leaf out. Although this is still the most efficient timing to apply nitrogen, I have since learned that there is some level of root uptake of nitrogen during the period of delayed-dormancy (bud-swell). This occurs due to nitrate, being found in a greater concentration outside of the root moves into the root to establish equilibrium. The higher

Sourced from AccessScience topic of soil chemistry. Water moves within plant-soil system from wettest to driest. This gradient is termed water potential, and explains why irrigation works. Basically, the water potential gradient between the soil and the plant, from wettest to driest, would be wet soil, dryer soil, root, stem/trunk, branch, leaf, and finally, air. Water, when applied through irrigation or rain, will follow that path, moving through the soil, into and up the tree, and out the leaves through the stomata.The final destination for the water molecule is the driest environment, which is air. As an analogy, think of the plant as a wick of an oil lamp, as the oil is burned, oil moves up the wick out of the reservoir to the point of being burned, keeping the lamp lit. For more information, please follow the links for water potential and the process of mass flow. Since nitrate, the only form of nitrogen that is used by plants, is a water-soluble negatively charged particle (anion), it does not bind with most soils, and therefore remains in the water solution within soils. Once in solution, it moves with the water. As water moves into the plant’s roots and up into the plant, nitrate enters the root and plant as well. If there is no or low water demand by the plant due to conditions of dormancy, very little of the nitrate-water solution will move into the plant. Only when the process of transpiration begins does nitrate move into the growing tips of the plant, providing nitrogen, an essential element for plant anabolism. Since leaves are needed on the tree in order for transpiration of water to occur, applications of nitrogen before leaf-out are at risk for loss due to leaching from the root-zone. For example, lets say that