Investigating the Ecological Impact of Pairing Agroforestry Establishment with Biochar Production

Data was collected on our shelterbelts and experimental fruit trees 2-6 times a season. Qualitative data collection for all trees included noting which trees had survived to first spring (and, eventually, second spring); health of tree including pest damage, leaf health, and sapling ability to support itself; and general field needs, such as mowing, mulching, etc. Quantitative data was collected on our experimental fruit and nut trees, which included Asian pears, American persimmons, three apple varieties, and hazelnuts. We elected to conduct four smaller the field trials on different species, rather than one larger field trial on the same species, to both observe if some species respond significantly to biochar as a soil amendment, and also to have a variety of fruits and nuts to offer to our community when the trees mature. Species were chosen primarily to cultivate native varieties when available, and to supplement with non-native trees to increase our product diversity in the years to come.

We are expecting to see fruits developing on these trees sometime between 2024-2026. To account for land usage without product yield, we implemented an alley cropping system on our asian pear and persimmon orchards. Between these trees, we grew winter and summer squashes, leafy greens, tomatoes, root vegetables, and more, harvesting hundreds of pounds of produce from these orchards. Compared to the hazelnut and apple orchards, which were not alley cropped, the pear and persimmon growth did not seem to be hindered by the vegetable production occurring between them, and, if anything, tending to the land around the trees kept these trees better mulched and weeded, and made managing these trees easier in a 1000+ tree agroforestry system. Thus, we recommend to any farmer who is considering incorporating trees into their agricultural system to employ the alley cropping method to reduce land space costs and ease farm management. In areas of the farm that were less suited to alley cropping, we planted trees where grass had previously been and we left the grass surrounding the trees, mowing it when necessary to avoid shading the young trees. 

Rather than a retort kiln, we compared biochar made in a Rotatable Covered Cavity (RoCC) kiln, and in an open-flame Kon-Tiki kiln because Paul Anderson, inventor of the RoCC kiln, offered us a free kiln and to demonstrate how to best use it. We noticed that the resulting biochar appeared similar between the two kilns. We have not yet been able to conduct lab analysis on the RoCC biochar to compare with the analysis of the Kon Tiki biochar analysis. One benefit to the RoCC kilns was that larger wood could be used, requiring less manual chopping prior to burning. However, there was more smoke and the kiln was more difficult to interface with as people conducting burns.

As noted in our initial application and midterm report, we want to carefully consider in the reporting of data that in field trials of scale this small, it is difficult to produce statistically significant results. However, based on our qualitative and quantitative data, we can comfortably say that biochar as a soil amendment did not hinder the tree growth, and, if anything appears to have supported it. 

To further explain this, let’s analyze the quantitative data collected from American persimmons, which were planted in September of 2021. Please refer to the table below, which has some of the data points from the beginning and end of the 2021 and 2022 growing seasons. Rows highlighted in red indicate experimental trees. All measurements are given in inches.

It’s evident that there is a wide range in tree health and growth both within and across the experimental and control trees. Note the differences in tree height between P-5 and P-2, as well as between P-12 and P-18. That said, on average, the trees planted with experimental values of biochar grew faster. Average growth in height from 9/29/21 to 10/12/22 was 14.3 inches for our experimental trees, compared to 6.6 inches in our control trees. Also, notably, while all trees made it to the first spring, two control trees did not make it past the fall of 2022. 

Based on the height data of our 18 apple trees of the ‘Goldrush’ cultivar, it is difficult to produce statistically significant results due to the small sample size and time frame. The table and graph below show our results. Control lines are indicated in black and biochar treatment lines are indicated in red. Overall, all trees demonstrated relatively consistent growth with no strong outliers. The average height at the beginning of the period was 49.3 inches for both control and treatment trees; 109.7 inches and 110.3 inches, respectively, for control and treatment trees at the end of the period. Trees between the two groups did not demonstrate any notable differences in herbivory and foliar health. The plastic tubes that encased each tree for protection against large herbivores likely provided a sheltered environment for pests, with no significant distance between each tree for pests to travel.

We intend to continue gathering quantitative and qualitative data on all of our trees as they mature to continue observing the effects of biochar as a soil amendment.

As part of our mission to build a better food system and tackle climate change, we hosted several field days and community events in partnership with The Land Connection, Savanna Institute, and Yale University, bringing in around 70 community members, farmers, and scientists to tour our farm and agroforest, learn about our climate solutions, and build local and regional relationships.