Application Timing Effects of Microbial Biostimulants on High Tunnel Vegetable Production

Project Timeline

November 2018

Spinach growth was monitored on November 13, 20, December 4, and 11.

Spinach plants were inoculated on November 16.

October 2018

Spinach was seeded on October 26.

The juice of pre-selected carrot samples was collected after being press using a standard garlic press. Any remaining solids were are allowed to settle out of the juice. Juice was placed in a handheld refractometer to measure the soluble solid content or °Brix.

June 2018

°Brix was measured for high tunnel, spring-grown lettuce on June 27.

May 2018

Spinach was evaluated for weight and leaf surface area.

Spinach was harvested on May 11 by selecting 1 square foot sample areas

Carrots were weighed, trimmed, measured, and prepped for quality analysis on May 30 and 31.

Carrots were harvested on May 30.

Lettuce was harvested on May 9 and evaluated.

April and May 2018

Lettuce growth was monitored on April 20, 26 and May 4, 9.

Growth of spinach was monitored on April 25, May 4, and May 10.

Growth of carrot was recorded on April 18 and 26, May 4, 10, 18, 25, and 30.

April 2018

Lettuce transplants were inoculated with microbial products on April 6 and 20. It was important to make sure the product would be absorbed into the area surrounding the root zone of each transplant.

Spinach was seeded in a 30×80 feet high tunnel and irrigation lines placed.

Carrots were inoculated microbial biostimulants twice after seeding.

March 2018

Paris Island lettuce transplants were planted on March 22 in raised beds of a high tunnel.

Carrots were hand seeded March 13 in 20 raised beds situated in a 30×80 feet high tunnel.

Spinach samples harvested on March 1 were photographed, weighed, divided and measured for leaf area.

Spinach was harvested on March 1 using a 18×32 inch quadrat in each of the 96 plots of a 30×80 feet high tunnels.

December 2017 to February 2018

Photos were taken on December 5, 19, January 11, 26, and February 2 in order to track changes in growth of the spinach. Square foot frames are used to aid in the process.

December 2017

Preparations for below freezing outdoor air temperatures were made on December 5.

Seedling growth of spinach on December 4 and 5.

November and December 2017

Each lettuce transplant was hand inoculated with one of five different microbial-based biostimulant products on November 3 and December 1.

November 2017

Low tunnels protect lettuce transplants from low night time temperatures in late November.

Spinach seedlings on November 17.

Transplant growth at 10, 19, and 34 days after planting.

Spinach plots were established and direct seeded in early November in a 30×80 foot high tunnel. Emergence was first noted on November 7.


Nearly 2000 ‘Paris Island’ lettuce transplants were planted in raised beds on November 3.


May 2017

The other three halves were used for internal colorimeter readings. Then roots were stored at -20° C for Brix measurements.

Then, roots were cut into half. Three halves were weighed and dried in oven.

External colorimeter reading was then completed using a Minolta Chroma Meter CR-300.

Three representative roots were sampled from each treatment and weighed before quality measurement.

Three representatives were sampled and measured for root length, shoulder and tip diameter.

Marketable roots were weighed for total fresh biomass.

Harvested carrots were washed and sorted.

Carrot was harvested on May 15, 2017.

Saps were then diluted into 50% of original concentration and pipetted into groove of nitrate meter to measure NO3 – N.

Sections closer to leaf were squeezed to collect saps.

Spinach leaf nitrate was measured using a Cardy Nitrate meter. Ten intact leaves were sampled and petioles were dissected and cut into half.

April and May 2017

Above ground and root developments of carrot are being monitored.

April 2017

Spinach was harvested on April 28, 2017. One square foot quadrat was harvested for each treatment within a rep.

Lettuce was harvested on April 27, 2017.

Spinach will be harvested in a week.

Lettuce is to be harvested in a week.

Lettuce transplants are growing well.

Carrot and spinach started germinating on late March.

March 2017

Microbial inoculant solution was applied to the beds by drenching.

Added product solution to water can (other containers such as spray tanks, drip irrigation systems etc. can be used), and then added more water to dilute to the desired volume (in this case, total volume is 2000 ml). Note: application of product can be via multiple ways, including sprinkler, tank, water can, drip irrigation (through injection), and pressure spray (backpack).

The bottle was shaken and agitated to let the product evenly mix in the water and added water to 1000 ml. Note: some products are dissolvable but others can only suspend in the water.

Weighed products were added to a bottle filled with water, and then added water to tube to rinse the remaining product.

Keeping the soil surface moist before applying products favors microbes to move to seed/root and prevents microbes from drying out.

Over 1,150 lettuce transplants were planted on March 21 into each of two high tunnels that were prepared in February.

More than 5,700 carrot seed were hand sown into raised beds inside of a high tunnel at the OARDC on March 17.

Zheng Wang assists with planting spinach seed on March 15 in high tunnel at the OARDC in Wooster, Ohio. Irrigation lines are placed and running.

February 2017


High tunnel soils were sampled and prepped for planting of lettuce transplants in March.