As part of my bachelor of honours degree in Environmental Science at Stirling University, I was able to conduct novel research in my own self-contained project and all in all I am truly happy with the results. Since I already knew that my academic future may lie somewhere at the intersect of agricultural productivity and nature conservation, an agroecological study was just the right choice for me. More specifically, I was investigating the potential of using insect poop or in more technical terms “insect faeces”, and its potential for increasing plant growth in spring onions, which can potentially also increase quality of life for subsistence farmers in Sub-Saharan Africa through higher plant yields. Furthermore there is a high potential to preserve or even increase ecosystem health through reduced pesticide and inorganic fertiliser inputs. My project was part of the bigger Ento-prise project, which looked at several facets of insect frass in a social and ecological context.
To really be able to investigate the potential of insect frass, I also studied naturally decomposed compost, which originated from the same source material (banana, avocado and mango peels) as the insect frass. This allowed me to truly attribute my plant growth results to the processing techniques (insect larvae consumption or natural processing) rather than to the source material itself, which was not part of this study.
In order to allow for equal soil conditions in all my plant pots, I had to sieve the soil (2mm mesh), which I excavated from an unimproved (no fertiliser or other inputs added) grassland at Stirling Campus. However, due to the high moisture content of the soil, sieving became rather impossible and kept clogging my mesh, which then turned rather impenetrable. I thus ended up drying the soil first by spreading it into numerous trays with minimal soil depth and exposing it to room temperature. A rather tedious job but with great results!
The sieved soil was then mixed with the different inputs (compost, insect frass and NPK fertiliser) at different rates and placed into plant pots in which spring onion seeds were thereafter sown. I decided to grow the plants in a controlled environment by using climate chambers in which I could accurately control light intensity, humidity and temperature. With the unpredictable and often harsh weather in Scotland, this growth experiment would have been very difficult to implement outside and the controlled environment thus allowed me to create a climate that at least partially resembled conditions in Sub-Saharan African.
Before I started growing my plants however, I undertook measurements of the soils to determine its quality, which is an important consideration since soil quality can also significantly impact upon plant growth. I achieved this by taking pH as well as Electrical Conductivity (EC) readings, which gave me a really good indication of the soil quality by using actually very simple instruments. In order to take accurate readings however, a careful methodology is highly important, which in my case included the mixing of a specific amount of soil with distilled water (distilled water does not affect the pH nor EC of the Soil). Subsequently probes were submerged into the soil-water solution and after a specific amount of time removed again.
Another soil measurement I undertook was the determination of organic matter content in the soil, since it can also greatly affect plant growth. This, too, is a very simple method! You dry the soil in an oven at around 90 degrees overnight to ensure that no moisture is left in it, since moisture is not what you want to be weighing. Then you weigh the completely dry soil and leave it in a special oven at 450 degrees over night. This will basically burn all organic material, thus releasing the carbon into the air and consequently leaving you with only the mineral content. After you have weighed the mineral content of the soil, you can now determine, using the two established weights, the proportion of organic matter in the soil. Simple!
Throughout the plant growth experiment, I also undertook a variety of measurements at regular intervals, most importantly plant height. I undertook these measurement in a very simple manner as well, by utilising calipers with which I measured the distance from the top of the soil substrate to the highest point of the plant. While this may not be the most representative measurement for plant growth, it nevertheless was easy to measure and provided me with a lot of data, which I could visually arrange easily to be viewed as a plant growth curve.
After I had conducted all of the aforementioned measurements and my little spring onions had turned into very much harvestable adults, it was time to carefully excavate all plants from the soil to be able to weigh the root as well as the shoot content of all plants individually, since knowing the ratio of root and shoot weight is again a great indication for potential plant stresses, because many plants will develop more extensive root systems, if nutrient uptake becomes more difficult in the soil. However, while this all may sound very logical and straight forward, the actual separation of the individual plants in each pot was certainly not, since the roots of several plants had to be entangled first.
Finally, I had gathered all my necessary data, thus enabling me to move on to analyse and consequently visualise it in graphs and tables in order to see possible trends between my different inputs and plant growth.