Application Timing Effects of Microbial Biostimulants on High Tunnel Vegetable Production

Project Timeline

March 2018

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.