Biochar, Compost, and Microbial Soil Amendments to High Tunnel Organic Romaine Lettuce.

Organic romaine lettuce was grown in a plastic covered high tunnel (16 feet high and 40 by 80 feet).  The soil was a Mountview silt loam that had compost applied the previous year. The project was conducted by students in an Organic Farming class at the University Organic Farm.  The objective of the study was to evaluate biochar, compost and a microbial mix on romaine lettuce yield.  Soil pH, CO₂ respiration, water infiltration, mychorhiza, and root mass and length were determined. Eight soil treatments replicated four times were applied to the raised beds plots, which were 2.5 by 4 feet with a 1 foot buffer.  Treatments included a control, compost, biochar, microbe, compost and char, compost and microbe, char and microbe, and char, microbe and compost.  Compost, biochar, and the microbial mix were applied equivalent to 20 tons/acre, 3 gallons/plot, and at 1 teaspoon/gallon/plot, respectively.  The soil amendments were applied September 9, 2012. Romaine was transplanted October 9, and plants harvested November 8.  Soil pH and electrical conductivity were measured in the field on October 7 and November 6 at three locations in the plots and averaged.  Mychorhiza was determined by subsampling the roots and clearing, staining and counting stained roots on a grid using a proxima projector to magnify the root grid. The middle ten romaine lettuce plants were harvested minus the largest and smallest plant for a total of eight plants and were immediately weighed.  Root mass and length were obtained from the largest plants in the plots and mychorhiza determined.  Romaine averaged 82.8 g per plant over all treatments. There was no difference between treatments with romaine yield at the 95% level using SAS.  Soil pH varied from 6.3 to 7.7 with the biochar treatments have the highest pH and the control and microbe treatment have the lowest.  Mychorhiza, root mass, respiration and water infiltration results will be presented.