Applications of Stimplex™ , An Extract of Ascophyllum nodosum, Improve Apple Yield under Both Water Stress and Fully Irrigated Conditions

Limited water for agricultural production is becoming more of a commonplace.  Water can be less available due to drought, or reduced water availability due to other demands.  The objective of this study was to evaluate the effect of a commercial extract of Ascophyllum nodosum (ANE) (Stimplex™, Acadian Seaplants Limited) on yield and fruit quality of apples under full irrigation and water stress conditions.  The experimental orchard was a block of ‘Top Export Fuji’ at the University of Idaho Parma Research and Extension Center.  ANE treatments consisted of control, ANE foliar, and ANE foliar plus soil applications.  Both ANE treatments received foliar applications at tight cluster, petal fall, and 5–10 mm fruit.  The foliar plus soil treatment received additional soil applications, once per month, throughout the growing season.  Beginning with the first irrigation in May, trees received irrigation at either 100% or 65% crop evapotranspiration (ETc). Tree growth, yield, and fruit quality data were collected.  There were no statistically significant differences in shoot growth and most quality attributes between the controls and ANE treatments under either irrigation level.  However, under water stress, ANE foliar + soil treated trees had numerically longer shoots than the water stressed controls.  Individual fruit weight was similar across all treatments.  Water stress reduced total yield per tree, by reducing fruit number, not individual fruit weight.  In both 100% and 65% ETc, ANE treatments significantly improved yield.  ANE treated trees under 65% irrigation had total fruit weights per tree similar to the fully irrigated trees, while control trees were lower.  Applications of ANE may have resulted in a reduction of  “June drop” or reduced the effect of environmental stress leading to increased fruit set.  The increased set did not result in a decrease in fruit size.  There were no differences in fruit color across any treatments, however there were some differences in soluble solids and starch degradation pattern.  Previous studies have shown that ANE can reduce water stress and wilting as well as improve plant growth and water status under water stress in potted herbaceous and woody plants.  This trial extends the benefits of ANE applications under water stress to yield in a commercial production system, and also supports previously demonstrated benefits non-stressed apple production systems.