Humate-Based Biostimulants Do Not Consistently Increase Growth of Container-Grown Turkish Hazelnut

Abstract

Humate-based products have been aggressively marketed to nursery producers as biostimulants which increase plant growth. Reports of their effect on container-grown trees in organic substrate are few. We tested four distinct types of biostimulants on top and root growth of Turkish hazelnut (Corylus colurna L.), grown in containers with pine-bark substrate. Treatments included: 1) an untreated control; 2) humate, applied as a dry topdress; 3) humate, formulated as a wettable powder and applied as a substrate drench; 4) humate, applied as a pre-plant root soak; 5) humate, to which various purported root growth-promoting additives had been added, also applied as a root soak. All treatments were tested within low, medium, and high fertilizer application regimes. No treatment increased top growth compared to untreated trees, and the root-soak treatments had the lowest top growth. At high and low fertilizer application rates, root length was similar for all treatments except for root-soak treatments, which had lower root lengths. At the medium fertilizer rate, root length was greatest for trees treated with granular humate applied as a dry topdressing and lowest for trees treated with root soaks.

Evaluation of Biostimulants to Control Guignardia Leaf Blotch (Guignardia aesculi) of Horsechestnut and Black Spot (Diplocarpon rosae) of Roses

“…Reasons for this lack of pathogen control efficacy can be suggested by reference to the use of biostimulants for other purposes. For example, biostimulants have been advocated as a means to enhance transplant survival of trees and improve crop yield and quality; however, similar to the results of this study, little influence of biostimulants on these parameters was recorded (Kelting et al 1997;Thalheimer and Paoli 2001). Contradictory to this, Thomp- Note: 1 = No pathogen attack observed; 2 = less than 5% of leaf area affected; 3 = 5%-20% of leaf area affected with some chlorosis; 4 = 21%-50% of leaf area affected, significant leaf chlorosis; 5 = 51%-80% of leaf area leaves affected, severe leaf chlorosis; 6 = 81%-100% of leaf area with complete leaf chlorosis.…”

Response of English Oak (Quercus Robur L.) Trees to Biostimulants Application in the Urban Environment

“…Russo and Berlyn (1990) stated that organic biostimulants improve root and shoot growth, increase resistance to stresses (both biotic and abiotic), and reduce the need for high levels of nitrogen fertilization through increased efficiency of nutrients and water uptake. However, some controversial results do exist, especially regarding their effects on root growth (Laiche 1991;Kelting et al 1997;Kelting et al 1998a;Kelting et al 1998b).…”

Failure of Foliar-Applied Biostimulants to Enhance Drought and Salt Tolerance in Urban Trees

“…Work by Barnes and Percival (2006) concluded that two biostimulant products that are frequently used in the UK and the United States, when applied at differing concentrations to reduce transplant stress, had few positive effects on growth and vitality of trees at week 8 and 20 after bud break. Indeed, many studies on trees indicate little or no effect of bistimulants upon alleviating stress (Kelting et al 1997;Thalheimer and Paoli 2001;Ferrini and Nicese 2002;Gilman 2004;Sammons and Struve 2004;Banks and Percival 2012).…”