Arboriculture & Urban Forestry 42(2): March 2016 Barnes 2007). Consequently, research has evalu- ated the potential of numerous soil amendments at the time of planting to include mycorrhizae, biostimulants, sugars, and fertilizers. Results have been mixed with some studies demonstrating posi- tive benefits on root vigor following addition of these amendments, while others little, if any posi- tive effects (Hensley et al. 1988; Edmeades 2003; Percival et al. 2004; Percival and Barnes 2007). Biochar is the solid co-product of biomass pyrol- ysis, a technique used for carbon-negative produc- tion of second-generation biofuels. Biochar can be applied as a soil amendment, where it perma- nently sequesters carbon from the atmosphere as well as improves soil structure, nutrient retention, and crop productivity (Elad et al. 2011). Evidence exists that biochar will alter the physical nature of most soils to increase the water-holding capacity by increasing the soil surface area as well as pore space to improve drainage problems in clay soils (Lehmann and Joseph 2009). Adding biochar to soil can also result in reductions in acidity, improve- ment of the cation exchange capacity accelerating the composting process, and improved habitat for beneficial soil microbes, which can indirectly cause an increase in plant productivity (Blackwell et al. 2009). Bamboo char has been to shown to com- prise of a broader range of pore sizes (0.001–1000 µm diameter) compared to wood-based biochar (10–3,000 µm diameter) (Thies and Rillig 2009), possibly enhancing the range of benefits provided by biochar originating from differing feedstocks. Sugar has a dual function in plants, as both a nutrient and a signaling molecule (Roitsch 1999; Rolland et al. 2002). Energy expenditure in plants is necessary for establishment (root formation) and survival (respiration), consequently supplying the end product of photosynthesis (i.e., sucrose) as a soil amendment may allow plants to invest more energy in reversing losses encountered through transplanting (Percival 2007). Slow-release sugar compounds, such as molasses, have been proven to have significant effects on plant growth during germination, influencing the mobility of nutrients, shoot and hypocotyl development including sup- pressing elongation, cotyledon greening, and expansion (Rolland et al. 2002). Evidence from sev- eral experimental studies shows that sugar supple- mentation to young and mature trees can enhance 103 root invigoration by increasing lateral root growth and root metabolism (Percival et al. 2004). Sugar as an organic amendment also has the potential to alter the soil rhizosphere populations, resulting in changes in plant nutrient uptake in favor of increased root growth (Blunden and Woods 1969). BOOST Organic Granular is a premium-grade compound organic fertilizer with an N:P:K ratio of 9:6:3. Slow- and quick-release nitrogen is present to provide both instant greening and longer nutrient availability to the root system aſter application to the rhizosphere. Studies investigating the applica- tion of soil-incorporated synthetic fertilizers on establishment and growth of Magnolia grandiflora and silver maple (Acer saccharinum) transplants reported significant increases in stem diameter, height, and growth by the third growing season, (Schulte and Whitcomb 1975; Hensley et al. 1988). However, further studies using Pyrus calleryana ‘Bradford’ indicated no benefits from incorporat- ing fertilizer at the time of planting, if the soil is already of sufficient fertility (Shoup et al. 1981). Consequently, data exists investigating the effect of synthetic fertilizers on tree growth; however, little work has been carried out studying the influence of organic fertilizers. Edmeades (2003) concludes that effects from long-term applications of organic and synthetic fertilizers are similar with both inducing large effects on soil productivity. There- fore, organic based fertilizers may have similar long term beneficial effects for transplanted trees. This trial’s approach of the use of an organic fertil- izer to stimulate root growth aims to generate new information. Likewise, although the influence of each of these soil amendments (biochar, molasses, organic fertilizers) has received some attention when applied individually the influence of com- bining these products has never been evaluated. The objective of this study was therefore to evaluate the potential of these three soil amend- ments (biochar a purified form of carbon, a slow release molasses fertilizer and a organic N:P:K fertilizer) singly and in combination. MATERIALS AND METHODS Bare-rooted Pyrus communis ‘Williams’ Bon Chré- tien’ trees obtained from a commercial nursery grower (Blackmoor Nurseries, Blackmoor, Nr Liss, Hampshire, UK) were used for experimental pur- ©2016 International Society of Arboriculture
March 2016
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