The 2012 ASHS Annual Conference

Previous research on wood-based greenhouse substrates has reported enhanced root growth of herbaceous plants compared to traditional greenhouse substrates. These reports have not adequately explained or quantified the differences in root growth that have been observed. Several new techniques are being developed and investigated as potential new methods of assessing and quantifying root growth, one being the use of the Hydraulic Conductance Flow Meter (HCFM). The HCFM provides a value of root conductance which is reflective of root mass and development. Shoots can also be measured with the HCFM, and these values with root conductance values can be correlated with dry weights as an assessment of overall growth.  Freshly harvested loblolly pine (Pinus taeda L.) was hammer-milled through a 6 mm (1/4 in.) screen after being initially processed either through a wood chipper or wood shredder. Perlite (PL), wood chips (WC) or shredded wood (SH) were amended to peat (v/v) at 15, 30 and 45% making a total of nine substrates. On 1 Feb. 2012, uniform seedlings of Tagetes erecta ‘Inca Orange’ (marigolds) were transplanted into 1-L plastic pots with six replications of each substrate. Marigolds were grown for six weeks, at which time plants were prepared for root conductance measurements. Plants grown in 15% WC or SH amended substrates had higher root conductance values than plants grown in 15% PL amended substrate which tended to correlate with root mass development. Root conductance in substrates amended at 45% incorporation was similar across all three components (PL, WC, and SH). This data suggests that root development is enhanced in wood amended substrates at smaller percentages of incorporation. Further investigations using this technique may provide direct correlations for quantifying root system development of greenhouse crops during production.