Soil Applied Post-Harvest Almond Tree Nutrition

Like farmers, almond trees continue to work after harvest and superior crops require optimum input management, including post-harvest fertilization and irrigation. In fact, the post-harvest nutrition management program is critical because the yield potential for the next crop is determined by bud formation on this year’s fruiting spurs. Next year’s bloom and nut set can only occur on the flower buds that are already created. Application of up to 20% of the total crop nitrogen demand after harvest will help ensure adequate nitrogen nutrition is available for this critical process.

Applying YaraLiva CAN-17 or YaraLiva CN-9 in the post-harvest irrigation will provide your almonds with readily available nitrate-N as well as calcium which is a critical component of good soil and tree health. Nitrate-N is the preferred form of nitrogen for many crops because it is immediately available for root uptake and there is no concern about ammonium toxicity. YaraLiva CN-9 has almost all the nitrogen as nitrate while YaraLiva CAN-17 provides your trees with 2/3 nitrate-N. 

In addition, YaraLiva CAN-17 and YaraLiva CN-9 supply water soluble calcium which promotes stronger cell walls and more robust cell membranes which help plants avoid pathogens and reduce environmental stresses such as heat and cold. Moreover, calcium works hand-in-hand with potassium to help plants respond to water stress.

Building strong cells within almond flower tissues increases tissue strength. While there is no specific research data, one can assume that a stronger flower will be better able to withstand frost conditions common during the bloom period. Calcium is also critical for root health and optimal soil structure. While fall root growth is slower than in the spring, calcium that is available in the soil is often depleted after a year’s worth of irrigation applications. Strong root growth during the post-harvest period is important for spring root reactivation after dormancy.

Potassium nutrition for almonds

Almonds take up large amounts of potassium – almost 80 lbs of potassium per 1,000 lbs of nuts. Potassium will be depleted from the soil resulting in declining soil productivity unless the potassium that is removed in the nuts is replenished through fertilization. 

Potassium fertilizer should be applied in the fall before rain starts. First, this minimizes the potential for soil compaction that can result from driving heavy equipment on wet soil. Second, the winter rains will move the potassium into the soil where it will be available to the roots next spring and summer. 

Sulfate of potash (SOP) is the preferred potassium source because it does not contain chloride that can damage sensitive almond roots and it has the lowest salt index of the common potassium fertilizers.

Partial salt index of four common potassium fertilizers

Suggested SOP rates based on yield goals

SOP applied in sandy soils or soils with low cation exchange capacity can be split into spring and fall applications. While weather conditions may prohibit this practice, consult with your advisor as to whether this might be a beneficial course of action.