2013 ASHS Annual Conference

Due to several environmental and economic factors, the use of the main physical components in common substrates utilized for growing horticultural crops—peat and bark—have either become of limited supply, costly to use, or both. This research looks at composted algae as an alternative substrate for growing the woody nursery crop Ligustrum japonicum.  Plants were purchased as liners and stepped-up to 11.4 L containers over a 12-month period with the experiment continuing for another year.  At 24 months after transplant, data on physical parameters were collected: growth index, SPAD, trunk diameter, and shearing biomass (to 20 cm from side of pot to 40 cm tall from substrate surface).  Treatments consisted of three substrates: Taylor Creek composted algae (TC-CA), Egret Marsh-CA (EM-CA), a peat-based substrate control (PB), and three controlled-release fertilizer (CRF) rates: 0%, 50%, and 100% of the label recommended rate (0, 50, or 100 CRF).  The experiment was a completely randomized design with six replications per substrate x CRF combination.  In the 0 CRF treatment, plants growing in TC-CA or EM-CA when compared to the PB control were significantly greener by as much as 10 SPAD units (52 PB and 62 EM-CA SPAD), had a larger trunk diameter by 8 cm (17 cm PB and 25 cm TC-CA), and a greater growth index by 27 cm (37 cm PB and 64 cm EM-CA).  For all CRF rates, plants growing in either of the composted algae substrates when compared to the PB substrate had significantly greater biomass removed from shearing by an average of 57% (436 g FW for PB and 780 g FW for CA).  This research demonstrates that composted algae is a suitable, if not superior, substrate for growing Ligustrum japonicum compared to the PB control substrate.  Using composted algae, based on the 0 CRF treatment, may require fewer nutrient inputs to produce a marketable plant.