We all know that an adequate and balanced supply of all mineral nutrients is critical for optimum fruit set. I think this year is going to be especially challenging given the amount of rain that we’ve experienced and the amount of mineral flush and heavy leaching of the soil that has subsequently taken place. The exact amount of leaching is difficult to quantify. The answer depends on site-specific soil conditions and the effectiveness of the rainfall. Sandy loam soils have limited ability to hold nutrients to begin with so some soils will be more greatly impacted. Leaching does occur when water moves into the soil, but not all the nutrients (present as anions and cations dissolved in the soil solution) are leached.
Potassium, nitrogen and sulfur are the most mobile nutrients but even nutrients such as magnesium, which is held more tightly than potassium, can be depleted due to excessive rainfall. Nutrients that are leached below the rooting are at least temporarily lost from the system although they may be recycled if roots grow deeper. Nitrate leaching is also a significant source of soil acidification or the buildup of hydrogen cations, also called protons, reducing the soil pH.
Given the amount of rain we’ve experienced in many parts of the country, including California, growers are going to want to give crops nutrient applications early on. Even when soil N is readily available at the time of budbreak, canopy demand exceeds uptake from the soil (Lohenertz, 1991). While the nutrient uptake capacity of vines can increase shortly after budbreak, the majority of nutrient uptake from the soil has most often been found to occur between bloom and veraison. Again, with the wet soils this year, this will be especially true and getting vines ready for a consistent and even bloom and set will require foliar fertilization applications.
We would recommend getting nutrient foliars on early starting at 5 inch shoot growth. We like our OMRI listed foliar fertilizer, Agroprime or sustainable products, Agrostim and Supergrow. Aquasap, our OMRI listed dry powder seaweed extract can also be foliar applied.
I believe that our exceptional products can pave the way for improved flowering and set in any conditions but especially in a wet weather pattern.
