Cultural practices to speed the growth of microgreen arugula (roquette; Eruca vesicaria subsp sativa)

Microgreens are salad crop shoots harvested for consumption within 10 - 20 d of seedling emergence. A series of cultural experiments was conducted with the objective of lessening the greenhouse production time, and therefore the production cost, for microgreen arugula (Eruca vesicaria subsp. saliva) grown in peat-lite (a soilless medium). Sowing seeds at a high rate (55 g m(-2)) resulted in a greater shoot fresh weight (FW) m(-2) at 10 d after planting (DAP) than sowing at lower rates, although individual shoots were lighter. Two fertilisation regimes were examined: pre-plant incorporation of 500 - 4,000 mg N l(-1) supplied as ammonium nitrate, calcium nitrate, ammonium sulphate, or urea, and/or post-emergence daily fertilisation with solutions of 21-2.2-16.6 (N-P-K) at 0, 75, or 150 mg N l(-1). The two most economical fertilisation treatments to increase shoot FW m-2 were daily solution fertilisation with 150 mg N l(-1), or daily solution fertilisation with 75 mg N l(-1) plus a pre-plant media incorporation of 1,000 mg N l(-1) from Ca(NO3)(2). Irrespective of these two fertilisation treatments, pre-sowing germination (pre-germination) of seed by incubation in grade-5 exfoliated vermiculite (1.12 g seed in 157 g vermiculite) moistened with 2 g water g(-1) dry weight (DW) vermiculite for 1 d at 20 degrees C, resulted in a 21% increase in shoot FW by 14 DAP compared to sowing non-treated seed. Pre-germinated seed showed 81.5% germination, with radicles averaging 2 mm in length at the time of sowing.