Lettuce Seedling Trials
with assorted Biochars & Fertilizers
First, Second, Fourth
My lettuce trials clearly showed biochar has significant effects on seedling growth. And biochar seems to work best at lighter doses—in the range of 5-12%.
Yet, my second trial results are again unexpected, plus my protocol was disrupted by dought, flood and other disturbances. My attempt to test sea minerals was a literal wash-out. So, I'm left with more questions, and mostly vague answers. Beyond toxicity tests, we must learn about the varied properties of different biochars, and how each contributes to soil structure, function and health. This calls for more replications to examine the observed effects, and check for consistent results.
Jim Welch and I now have retorts to make biochar, yielding steady supplies of various biomass materials—from straw to applewood (photo below). At the moment, I have eight distinct types of biochar. Corn stalks (stover) is another key on-farm feedstock to test, and I have a special interest in bamboo biochar. Each must be checked for toxicity to seeds, plants and soil organisms.
Saratoga Apple has 200 crates of dry applewood—a dense, difficult hardwood. But biochar made from straw and black locust bark has impressive lightness & porosity. Yet, while straw biochar easily crushes to powder in my hand, it may be hydrophobic (water-repellent) in soil. And twice we detected ammonia—the reduced form of N—when we opened a freshly-fired retort of charred straw. A few of many issues to explore in experiments.
This third trial also tests a variety of fertilizers. Saratoga Apple is shifting to "Nutrient-Dense" farming methods, emphasizing natural geological mineral sources over synthetic chemicals. The photo below depicts eight soil amendments. Clockwise, from the top (12 o'clock):
Leonardite (immature coal = geological carbon)
Florastim (composted sea floor clay)
Nutrient-Density (rockdust blend)
composted chicken manure (pellets)
SEA-90 sea minerals (dry crystals)
Planters II (gypsum (calcium sulphate) plus trace elements)
Rock Minerals (crushed mix @ center)
kelp powder (plastic cup @ 7 o'clock)
Traprock (meta-basalt) dust, greenstone and other geological materials are available to test and use in greenhouse beds. We also will test mineral fines from nearby quarries, especially glacial gravel dust. All these amendments are good sources of trace elements.
Saratoga Apple's second greenhouse will be complete in November, and beds must be formed and seeded immediately to establish a winter crop before solar influx weakens. My third trial seeded assorted greens into Accelerator trays with various biochars and fertilizers, and blends. In one month, these seedlings will be transplanted into greenhouse beds. Biochar will be added to beds and seeded with winter lettuce and spinach to monitor through the winter as a fourth trial.
In early October, I began to prepare Accelerator trays for this new, larger, more complex seedling trial. Rainy, windy weather slowed progress on this new trial, but currently, it includes 20 trays with up to 2240 seedlings.
These third trial trays were prepared and seeded in a series of groups, with 2 to 5 trays in each group.
Each tray was prepared with three blocks of 4 rows, plus 2 rows reserved as controls with potting mix only (yellow lines). Each block was carefully filled with potting soil blended with one test material at one of three rates: 20% (4:1), 10% (9:1), 5% (19:1). Fertilizer trays had two control rows together at the bottom; biochar trays had a control row between each 4-row test block. Every effort was made to establish a consistent, uniform framework of materials and organization so any differences are easy to identify visually and compare.
The photo below shows the 8 trays of groups A & B.
Trial groups A through E were seeded (left-to-right, green lines) with 2 columns (14 cells) of smooth-leaf spinach, 2 columns of savoy spinach, 3 columns of assorted winter lettuce, and one column of assorted greens (brassicas). Group F had the four rows of spinach replaced with full columns of broccoli, escarole, mustard, and chinese cabbage.
Trial 3 Results & Observations