106 Schaffert and Percival: Influence of Biochar, Slow-Release Molasses, and an Organic N:P:K Fertilizer molasses > BOOST Organic + biochar + molasses > molasses + biochar > biochar > molasses > con- trols, when averaged over two growing seasons. A similar ranking order was recorded for crown canopy coverage: BOOST Organic + biochar > bio- char > molasses + biochar > BOOST Organic > BOOST Organic + biochar + molasses > BOOST Organic + molasses > molasses > controls, when data was averaged over two growing seasons. Tree Vitality In both the first and second growing season, soil amendment with biochar, molasses pellets, and an organic N:P:K fertilizer individually increased tree vitality [chlorophyll fluorescence (PI), leaf chloro- phyll content (SPAD), and photosynthetic rates]. In the majority of cases, these increases were significant (P < 0.05). For example, increases in chlorophyll con- tent (SPAD) ranged from 4.5% (slow-release molas- ses pellets) to 27.5% (BOOST Organic), increases in PI values ranged from 13.7% (slow-release molasses pellets) to 59.9% (BOOST Organic), while increases in Pn ranged from 9.6% (slow-release molasses pel- lets) to 25.3% (BOOST Organic) over non-amended soils, when averaged over two growing seasons. Combination of amendments resulted in an increase in tree vitality [chlorophyll fluorescence, leaf chlorophyll content (SPAD), photosynthetic rates] compared to use of an amendment individu- ally. For example, in Year 1, amendment with biochar or BOOST Organic increased leaf chlorophyll con- tent from 38.7 (non-amended controls) to 44.5 and 49.9, respectively. Soil amended with a combination of biochar + BOOST Organic increased leaf chlo- rophyll content to 50.8. Averaged over two growing seasons, combining products enhanced chlorophyll fluorescence (PI), leaf chlorophyll content (SPAD), and photosynthetic rates by 12%–77%. Such a response indicates that combination of amendments tested in this study induce additive effects of tree vitality compared to individual application. Based on leaf chlorophyll content, positive effects were in the following order: BOOST Organic + biochar > BOOST Organic > BOOST Organic + biochar + molasses > BOOST Organic + molasses > molasses + biochar > biochar > molasses > controls, when averaged over two growing seasons. A similar rank- ing order was recorded for PI and Pn values: BOOST Organic + biochar > BOOST Organic + biochar + molasses > BOOST Organic > BOOST Organic + molasses > molasses + biochar > biochar > molasses > controls, when averaged over two growing seasons. DISCUSSION All soil amendments evaluated in this study im- proved transplant survival in the critical first growing season after planting. Although sup- porting evidence exists that amendments, such as carbohydrates, organic nitrogen formulations, and biochar, can positively influence transplant survival, this study generates new and novel data by assessing different formulations of each amendment to include a pelletized slow-release form of carbohydrate (molasses) rather than liq- uid, biochar derived from a purely bamboo feed- stock origin, and a new organic N:P:K fertilizer Table 1. The influence of soil amendments on growth, tree vitality, and mortality of Pyrus communis ‘Williams’ Bon Chrétien’ in Year 1. Treatment Control (no amendment) Molasses pellets Biochar BOOST Organic granular BOOST Organic granular + BOOST Organic granular + Molasses pellets + biochar biochar molasses pellets BOOST Organic granular + molasses pellets + biochar Tree vitality SPAD 38.7 42.3ns 44.5ns 49.9* 50.8* 47.9* 47.1* 50.3* Growth PI 6.2 7.1* 8.2* 8.2* 10.0* 7.4* 9.4* 11.1* Pn 4.01 4.45ns 4.48ns 4.56ns 4.66ns 4.38ns 4.61ns 4.50ns Fruit yield/ tree (kg) 5.8 6.1ns 6.6ns 6.8* 7.2* 6.7* 7.0* 6.8* Crown volume 0.60 0.68ns 0.77* 0.77* 0.88* 0.72* 0.81* 0.76* Mortality (%) 20 0 0 0 0 0 0 0 Notes: All values mean of surviving trees from an initial number of 10. Asterisk (*) = significant differences between means (P = 0.05). P < 0.05 are considered signifi- cant based on Tukey’s Honestly Significant Difference test. SPAD = estimated leaf chlorophyll content, PI = chlorophyll fluorescence, Pn = light-induced CO2 fixation. ©2016 International Society of Arboriculture
March 2016
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