Effects of Biodynamic Preparations on Compost Development
L. Carpenter-Boggs, J.P. Reganold, and A.C. Kennedy

Biological Agriculture and Horticulture 17:313-328. 2000

Biodynamic (BD) agriculture is based largely on scientist-philosopher Rudolf Steiner’s recommendations, including the use of herbal preparations that purportedly enhance compost quality. There are doubts among some scientists as to the value of BD practices. Furthermore, past studies have been criticized for possible researcher bias, lack of necessary experimental controls, and publication through non-refereed venues.

The present replicated (r=5) study compared composting processes and products obtained with vs. without BD herbal preparations 502-507. These preparations are, in numbered sequence, derived from yarrow blossoms (Achillea millefolium), chamomile blossoms (Matricaria recucitata), stinging nettle shoot (Urtica dioeca), oak bark (Quercus robur), dandelion flowers (Taraxacum officinale), and valerian extract (Valeriana officinalis).

Compost raw material was dairy barn waste, comprising manure and pine shaving bedding, with initial carbon-to-nitrogen ratio (C:N) of 55 to 60:1. Mean water content of the starting compost was 70 percent. Each of 10 compost piles measured approximately 2 x 2.5 x 1.5 m, with mean mass approximately 3.5 metric tons. Five of the piles were randomly assigned to receive the BD preparations, and five control piles remained. The preparations were applied as prescribed by BD practitioners, at concentrations of approximately 1.1 mg preparation per kg of compost. The piles were not turned, but were allowed to develop for eight weeks.

During the eight weeks, BD compost had significantly and consistently higher mean temperature at 55-60 cm depth. The pH was significantly lower in BD compost near the end of the eight-week period. The 24-hour redox change, respiration (CO₂ evolution per hour), and dehydrogenase enzyme activity were not statistically different for BD compost.

After eight weeks of development, BD compost had a significantly higher ratio of dehydrogenase-to-CO₂ and higher concentration of nitrate, but no significant differences in final carbon percentage, C:N, ammonium concentration, available phosphorus, available potassium, cation exchange capacity, or cation exchange capacity per unit carbon.

Phospholipid fatty acid profiles, used to distinguish soil microbial complexes, showed that BD compost had a higher indication of bacterial and a lower indication of fungal activity than did control compost.

One point of contention regarding BD practices is the use of such small amounts of the preparations. Carpenter-Boggs et al. noted that bioactive compounds (e.g., plant hormones) often show activity at concentrations below those used for the addition of BD preparations. The four medicinal plants used in the preparations (yarrow, chamomile, stinging nettle, and valerian) are known to contain a variety of bioactive compounds, which might be present in the BD preparations and act at low concentrations. The authors also consider that the BD preparations may have served as microbial inoculants, accelerating the composting process and otherwise altering the dynamics.

For more information: L. Carpenter-Boggs, USDA-ARS North Central Soil Conservation Research Lab, 803 Iowa Ave., Morris, MN 56267.

DEC. 606
Contributed by Robert L. Bugg