On-Farm Testing of Johnson-Su Compost Extract as a Biological Inoculant in Wheat and Soybeans

Bioreactors

• 4 Bioreactors were built by hanging bulk seed tote bags inside the cages of bulk shuttle totes, and hanging 5 perforated sewer pipes inside the tote to serve as the air chimneys. The bottom 6-8 inches of the inner plastic bladder were cut out and placed back inside the cage to catch any excess leachate from potentially overwatering the bioreactor. Pallets were cut to fit inside the cages and placed inside the plastic liner, below the tote bags to allow extra water to drain out of the tote bag and into the cut out bottom of the plastic bladder, which could be drained using the shuttle tote's ball valve if too much liquid accumulated
• Compost materials included a mix of approximately 50% rye straw chopped with a bale processor, 10% partially decomposed wood chips, 10% mulched oak leaves, and 20% horse manure mixed with hay. The manure was free of dewormer, and the straw was free of chemical residues. 
• Materials were mixed together in a wheel barrow, then transferred to laundry baskets and submerged in water until they were sufficiently soaked, drained for a few minutes and then  distributed around the chimneys inside each of the bioreactors
• An automatic sprinkling system was setup using garden irrigation drip line and an automatic timer for garden hoses to keep the compost moist. Bioreactor compost was also partially covered using scrap pieces of landscape fabric to reduce evaporation. 
• The bioreactors went through their heating cycle over the course of the first week and peaked at about 130 F
• After the bioreactor internal temperature dropped back down below 80F, approximately 2 lbs of red composting worms were added to each bioreactor. 
• Bioreactors were maintained in heated shops above 60F throughout the remainder of the year, adding water as necessary to maintain moisture so that the compost wasn't overly drenched, but a handful of compost squeezed in the hand could squeeze out a drop of water

Extraction and Application

• Fed N Happy worm castings were used in place of Johnson-Su compost in the 2023 growing season, since we did not have access to suitable Johnson-Su compost for the first year. We went with worm castings since the Johnson-Su process with worms essentially results in matured vermicompost, and Fed N Happy's  method of raising worms would result in a similar product suitable for comparison. A BeCrop DNA analysis of the worm castings revealed about 848 species of bacteria and 137 species of fungi present in the castings. 
• In 2024, compost extract from the Johnson-Su compost created in 2023 was used on-farm and in small plots. A RhizeBio DNA analysis of Johnson-Su compost revealed about 6000 species of bacteria/archaea and 60 fungal organisms present in the four bioreactor containers.
• Extract was initially made for the small plot research and the wheat seed treatments by vigorously bubbling 2 lbs of material (worm castings or compost)/gal in a 5 gal bucket using a circular lawn sprinkler attached to an air compressor at approximately 15-20 psi for at least 30 min. The extract was filtered first through a 5 gal paint filter, and then through a finer cone paint filter (micron/mesh size unknown). The extract for the on-farm field plots was additionally run through a system of T-line filters attached to a small sprayer pump set up by one of our cooperating farmers fitted with a 30 mesh and a 50 mesh filter. 
• Wheat seed was treated by spraying the filtered extract onto the wheat seed as it was being augered from a truck to the seed tender/gravity box at a rate of 9 0z/cwt, which is a similar volume rate for commercial seed treatments. Wheat seeds were covered and thouroughly mixed by augering, but were not so wet as to cause bridging or clogging problems. A 60 gal mixing cone held the extract and was attached to the T-line filter/pump sprayer set up with a fine nozzle tip. 
• An additional sunflower plot used a liquid in-furrow drip application at planting instead of a seed treatment. For this extraction, we used 1/3 lb compost/gal, applied at a rate of 6 gal/acre to reach a the rate of 2 lbs compost applied/acre suggested by David Johnson. Compost was again first bubbled inside a 5 gal paint filter hung inside a 60 gal mixing cone. A trash sump pump was also hung inside the mixing cone with a 1.5 inch hose attached, which was used to circulate and agitate the water and compost during the extraction. The initial extract was run through the T-line filtration set up and filtered down to 50 mesh before being transferred to the air seeder's rinsed starter fertilizer tank

On-farm Trial Protocol

On-Farm Plots

• At planting, wheat plots were fertilized with their respective fertilizer treatments using a pull-type spreader or the coop's spreader. The Johnson-Su treated plots were planted first with the treated seed, and then the untreated plots were filled in afterwards with regular untreated seed. 
• The other crop plots (sunflower, corn, pea) planted normally and without any fertilizer treatments, just turning the liquid system on and off through the respective treated and control plots as the field was planted.
• All plots were flagged and marked with GPS at planting
• Tissue samples were collected at late boot/early flag leaf stage in the wheat sites
• Plots were harvested with the grower's combine and weighed in a weigh wagon. Grain samples were collected to test moisture, test weight, and protein content.
• Soil samples were collected after harvest for nutrient analysis and PLFA testing
• Treatments were applied as follows:

2023

1. Control – Farmer fertilizer rate, no extract
2. Compost extract + ½ N rate + 0 P
3. Compost extract + 0N + 0P

2024

1. Control - 100% N rate
2. Control - 75% N rate
3. 75% N rate + compost extract

Small Plots

• Wheat and soybean small plots were set up as randomized split-plots, with the extract as the main plot and fertilizer treatments as the sub-plots. The wheat plot was replicated 3 times, and the soybean plot was replicated 4 times as field space allowed. 
• Wheat seed was treated with extract while the soybean plots received an in-furrow application. The extract was made by bubbling in a 5 gal bucket as described above, following the compost and application rates as described above for either the seed treatments in the wheat or the in-furrow rate for the soybean plot. 
• Tissue tests were collected at late boot in wheat and 3rd trifoliate in soybean
• Plots were harvested with a small plot combine by the U of MN Crookston plot technicians. Grain samples were collected to test moisture, test weight, and protein content.
• Soil samples were collected after harvest for nutrient and PLFA analysis
• Treatments were applied as follows:
  • 0, 120, 180 lbs N; with compost extract (wheat only)
  • 0, 120, 180 lbs N; no compost extract (wheat only)
  • 0, 40, 60 lbs P₂O₅; with compost extract (wheat and soybeans)
  • 0, 40, 60 lbs P₂O₅; no compost extract (wheat and soybeans)